A Collection of Unique Ideas for improving Marine Reliability, Safety, Comfort, etc..

    Do-It-Yourself instructions, drawings, parts lists, where to buy. Some KITS and/or parts available.

Anchor Alarm
Wakes you up if your anchor drags. Do-it-yourself instructions.
Auxiliary Battery Bank Adding a remote battery bank for anchor winch or bow thruster.
Battery Box How to install (actually how NOT to install) a battery box
Battery Saver Protect your battery banks from "short cycle" damage.
24 Volts from 12 How to get 24 volts for a bow thruster from a 12 volt system.
Combiner Specs. Never again get caught with a dead starting battery.
Trolling battery Charging a trolling battery automatically from an outboard.
Bilge Alarm. Save your boat from sinking.
Compass Software Software creates a deviation chart for your compass.
Dinghy Saver Protect your dinghy from theft.
Fire Prevention How to prevent 120v electrical fires from damaging your boat.
DIY Flag The easy way to make your own flag.
Head Flushing How to avoid extensive plumbing maintenance on your head.
Mildew Removing and controlling mildew on a boat.
Propane Switch An automatic propane shut-off switch and some great tips.
Pump Saver Prevents your pump from self destructing if it runs dry, for under $5.00.
Siphon Breakers - Vented loops Fix siphon breakers on vented loops so they stay working.
Venting Trapped Air. Automatic elimination of trapped air in filters, strainers etc.
new.gif - 1027 BytesPump Priming Automatic Repriming Centrifugal Pumps
Save Water Gadget to save precious fresh water.
Clogged Strainer How to clear clogged inlet strainers in less than 60 seconds.
Diving Compressor DIY diving setup using the Hookah type regulators.
Teak Decks How to maintain, clean but mainly how to Re-Caulk a teak deck.
Fixing Loose Teak Deck Plugs How to get teak plugs to stay in when the hole is too shallow.
Electrolysis A non-technical education on boat electrolysis and problem solving.
The Galvanic Isolator A brief description of the Galvanic Isolator, and how to test it.
Capacitor for Galvanic Isolator Does my Galvanic Isolator need a capacitor to conduct AC?
Combiner Remote Build yourself a remote indicator/control for the Combiner 50 or 150. (Not for beginners.)
2 part polyurethane How to mix small batches of 2 part polyurethane.
Mixing Lead-Acid and GEL batteries. Use our 150 AMP Combiner as a voltage regulator to charge AGM/GEL batteries from an alternator with an internal regulator set for Lead-acid voltages.
Refrigeration battery saver Automatically disable your refrigerator when there is no 12V charging source.
Depth marking an anchor chain. A simple scheme using only 3 colors that lets you read the depth from the marks on the chain without counting.
Anchoring in tidal areas How to set two anchors so you are not resetting them on tide changes and not twisting multiple rodes.
Teach Yourself Morse Code. A free program you can download that will do a good job of teaching you code.
Making Battery Cables How to solder the terminals on battery cables.

Prevent 120V Electrical Fires From Destroying Your Boat

When you have an electrical overload on your shore power or a generator, especially on an unattended boat, it can fall into one of two categories. If the current is greater than the fuse or circuit breaker setting, the circuit is interrupted and the fire is prevented. BUT if the current is high, but not enough to blow the fuse or breaker, that heat energy is being generated somewhere, usually in the wiring between the power source and the short or partial short. This heat will slowly heat the wire until the insulation starts to melt and smoke, then eventually catch fire. Electrical insulation smoke tends to be very dense and detectable.

The FIRE BREAKER consists of one or more smoke detectors placed in auspicious locations. The detectors should be of the Infra Red Optical type since they are much more immune to false alarms than the ionization chamber types, especially in a galley. Use the smoke detectors which have a radio transmitter included such as are used on central alarm systems (about $95 each). Install a radio receiver (about $45) beside the circuit breaker box and connect its output contact to a "Solenoid Trip" main breaker. This is a circuit breaker which has an additional magnetic coil which trips the breaker when 120 volts is applied to it.

Now when the smoke from the electrical fault is detected by the smoke detector it transmits a signal to the receiver which closes the 120 volt circuit to the main breaker which disconnects the power source before the fire starts.

The solenoid trip breakers are available to replace the main breaker in your electrical panel however they can be difficult to locate in the size and model required, and if you have an old fuse panel it is not practical but there are two alternatives - One is to install an additional main breaker before the panel which has the solenoid trip or second (but not recommended), install a heavy duty contactor which can close across the downstream side of your main fuse/breaker which will draw enough current when it shorts the power to blow the main.

WARNING: This project involves major wiring changes to your shore power connection. If you are not thoroughly experienced in electrical wiring practises, especially related to marine installations, you should have a professional installer do this work.

Parts List

Photo Electric Smoke Detector with Transmitter
Linear Corp. Model LN-373 about $95
Wireless Receiver, 12 volt,
Linear Corp Model LN-D67 about $45
More to come - including circuit diagrams.

Battery Saver

This is an empirical article is based on 10 years of cruising experience, with no technical verification.

WARNING, if you are not competent in 12 volt marine wiring practises you should have a professional installer perform this installation.

The deep cycle batteries or battery banks usually found in cruising boats were designed for deep cycling. This may seem rather obvious but it turns out that if you don't deep cycle them you can destroy them. This is no problem when you are cruising away from shore power but for those long stays at the dock you need to take protective measures.

With a battery charger maintaining a constant voltage, those intermittent loads such as flushing a toilet or running a water pump take just a tiny charge off the top of the battery capacity which is replaced in a few minutes by the charger. This short cycle, always at the same place on the battery plates can produce a layer which can materially reduce the capacity of your expensive battery bank and shorten its life drastically.

There are two solutions. One is to turn off your charger until the bank is about 20% discharged so that the battery is not short cycling at the same spot. This has the problem of remembering to turn it back on and also that you are using up the cycle life of your expensive battery bank. A much better solution is to completely disconnect the battery bank from your system and replace it with a regular automotive starting battery. These batteries are designed to operate in this manner and one small battery is adequate for supporting those intermittent 12 volt loads with the help of the on line charger. Now days you can purchase one for about $30.00 with a 3 to 5 year life guarantee. You probably are voiding the warranty by using it on a boat but you will be getting a battery that will support the load for many years at minimal cost.

West Marine sells an economical single pole battery switch which makes the changeover simple. Put one in series with the battery being isolated so it can be disconnected. Leave the cheapo 12 volt in circuit all the time - it adds a little extra capacity.

If your (now) isolated house battery is of the maintenance free type, it can be left idle for long periods with no significant loss of life but your should put them back on charge once or twice a year to keep them ready. If they are the lead-acid type, you will need to check the voltage more often.

WARNING, If you are using an inverter on the battery, make sure its capacity meets the requirements of your inverter manufacturer. Inverters can draw and charge with very heavy currents and damage to the battery and/or the inverter can occur if the battery does not have sufficient capacity.

HOW TO INSTALL (actually how NOT to install) A BATTERY BOX.

The typical battery box serves a number of purposes. In addition to mechanical support, the obvious one is to contain acid and water spills and the nasty damage they can do. There is, however, a very important function that is used rarely but can be vital to survival and a function that is often negated by incorrect installation.

The battery box is designed (usually) to protect the battery from salt water in the event of a dunking. During an emergency you could need the battery to get an engine started or maintain a bilge pump so you don't want salt water shorting it out, causing steam, chlorine or worse problems. This function is achieved by having a bubble of air trapped under the battery box lid. If it remains reasonably horizontal, it will also prevent water ingress to the box itself as the bubble extends down below the lip of the box.

So in view of this desired function, always make the electrical connections with the wire coming vertically through the access skirts in the lid. NEVER DRILL HOLES IN THE LID FOR WIRE ACCESS. Also, avoid purchasing battery boxes made by uninformed manufacturers that have "knock-out" holes or vent holes already in the lid.

Automatically disable your refrigerator when there is no 12V charging source.

This is a simple way to make sure you don't discharge or even destroy your house battery by forgetting to turn off your refrigerator load. Many installations only have the capacity to support the refrigeration while on shore power or when the engine is running. But a manual switch is often forgotten when you start the engine, wasting refrigeration time, or even worse, you forget to turn it off and deplete your battery after the engine is turned off.

The process can be automated by installing a Combiner 50 between the refrigerator and the battery. One red lead goes to each, and the black ground lead is connected to the 12 volts negative. Whenever a charging source raises the battery voltage above about 13.3 volts, the combiner will close and supply the refrigerator. When the voltage drops, it will disconnect. The built in timing circuits in the C50 will prevent short cycling that is detrimental to refrigeration motors. No power is used by the C50 when the refrigerator is not running.

If you want to be able to manual override the automatic control and allow the refrigerator to run while no charging source is available, you can add a small switch to the remote control feature of the Combiner 50.


Dinghy theft, especially when visiting overseas, can be a constant worry but for only $9.95 we have the ultimate solution, suitable for all types of dinghy up to 15 feet.

Introducing the BURGLAR PROOF KNOT

Tie your dinghy to a solid fixture using our BURGLAR PROOF KNOT. Although you know the secret and can tie and untie it in seconds, the burglar will struggle for hours and be thwarted. This secret knot, imported from India, comes with full instructions and a sample knot for only $9.95 plus $3.50 shipping by priority mail. Full refund excluding shipping if anyone (who has not been told the secret) can untie it and steal your dinghy.

This item now comes with a genuine CERTIFICATE OF AUTHENTICITY.

SPECIAL NOTE: This secret knot will not be sold to thieves. If you are dishonest, we will accept your order but will ship you a fake knot and will not refund your money.

Simple audio alarm can save your boat.

   If you can hear your bilge pump, its frequency of operation, how long it runs, if it runs at all and how long it stays off between runs, are all characteristics of your boat. Usually, long before trouble occurs you are aware of a change in these patterns, but if the pump is quiet you miss the signal or engine noise when underway can mask an impending emergency. A simple electronic beeper connected in parallel with the bilge pump can keep you informed and solve this problem. The beeper should be carefully chosen to have a distinctive sound so it is not confused with all the other alarms and it should be a comfortable sound so that you are not always tempted to turn it off, especially on a wooden boat where it may run periodically.

A signalling device which meets these requirements is the Mallory electronic Chime model SC616CP. It only draws about 6 milliamps but its distinctive bell chime sound is quite loud, it is easily identified and yet it is not objectionable. It mounts on any flat panel in a round hole about 1 1/8" in diameter. It is salt spray resistant from the front and the electronics is sealed in epoxy with terminals on the rear. It operates on 6 to 16 volts DC and you must observe the correct polarity when connecting it (but no damage if you screw up). Mount it in an appropriate location and wire it in parallel with the power going to your bilge pump so it "dings" when the pump is running. I installed a cut-off switch on Yandina but I have never had need to turn it off although I have been known to cover the chime to reduce the volume. Even if the operation is frequent, the sound is not objectionable considering the information it gives. Unfortunately this device costs about $40 but it is worth it for a premium installation. If there is enough demand to justify stock for a volume discount, Yandina Ltd., will make them available for $40 plus shipping, - call or email for availability.

Radio Shack sells a cheaper version for about $10, Catalog number 273-071. It uses 6 times as much power for the same output but this is still small compared with the pump itself. I assume it is not so waterproof and it does not mount flush on the panel.

If you have more than one bilge pump, you can wire them all to the same alarm using isolation diodes. On Yandina we have a display panel in the shape of the boat with LED indicators where the bilge pumps are located to show which pump is running, and a single alarm. You can download the circuit diagram if you are interested.

Chime, see above.
Isolation Diodes, any 1 amp diode from your local Radio Shack store, eg 1N4001, for about 50 cents, catalog number 276-1101.
12 Volt Panel Mount LED. You should use the ones with the resistor built in for simplicity and ease of construction. Radio Shack catalog number 276-084 for about $2.00 is excellent for operation on 12 volts.


Propane Safety:

Propane gas is heavier than air and will settle in the bottom of a boat to create a highly explosive atmosphere. To avoid catastrophic accidents, all propane tanks should be stored in an on-deck container which is vented on deck and sealed so that any escaping gas could not penetrate below decks. There should be a low level vent on the propane storage, just like a water drain vent so that any escaping gas can "run" overboard and a top ventilator is also advised to maintain air flow which will not only clear gas but reduce condensation and mildew.

The gas line to appliances below deck should pass first through a pressure reducing valve (the ones supplied for RVs are excellent, especially the two tank with automatic changeover). It should then pass through a solenoid valve which is operated by a 12 volt circuit so that the gas can be easily turned off from a remote station such as the galley. If you have a propane water heater, it should be fitted with a demand switch which turns on the electric propane valve and also automatically turns if off when the thermostat cuts off. All copper tubing below decks should ideally have no couplings or if they are necessary, they should be accessible for testing with soapy water.

Fail Safe Control Switch:

The traditional ON/OFF switch with light panel has the problem that if you forget to turn it off, you have defeated the whole safety design. Instead, purchase a 6 hour spring wound timer. The spring wind-up style which uses no power is quite reliable - I have been using one for 10 years now. They mount in a standard electrical box with the calibrated cover. Run the 12 volt solenoid supply through this instead of the ON/OFF switch. Drill a small hole and add a 12 volt LED indicator in parallel with the solenoid so you can see when it is on.

Now when you need to use the galley or appliance, estimate the time required and set the switch slightly above it. If you forget to turn it off, it does so automatically, maintaining the safety feature. In fact, for a 3 hour roast in the oven, you now have an oven timer.

Parts List

1.    Spring wound timer: Intermatic Model FF6H or equivalent. Check with your local electrical supply house. We have a few available at $29.14 plus shipping (maybe less if volume picks up).
2.    12 Volt Panel Mount LED. You should use the ones with the resistor built in for simplicity and ease of construction. Radio Shack catalog number 276-084 for about $2.00 is excellent for operation on 12 volts.
3.    12 Volt solenoid gas valve. West Marine Model number 308890, about $60.00.

Some special safety tips while on the subject of propane.

NOTE:- You should be familiar with all the conventional safety requirements for use of propane on board a vessel.

1.    How to test your system for leaks without any special equipment.

With the appliance off, or just after turning it off, turn the solenoid off as normal. This will leave the gas line pressurized and that pressure should remain undiminished for at least 30 minutes if there are no leaks in the low pressure side of your system. After 1/2 hour, turn the appliance on but leave the solenoid off, and with a flame or audibly listen for the supply line to release the small quantity of gas which still should be under pressure in the line. The amount will depend on the length of run and tube diameter but you should be familiar with what is normal and notice any degradation.

2.   Special warning about pressure regulator failure.

This is best explained by repeating the experience of a boater that was reported on the Cruising World Boating Forum. Summarized the story goes - The propane stove would not light one morning. The trouble was tracked down to the solenoid valve on the low pressure side of the regulator. It was getting 12 volts but failed to open. As a temporary fix to get a cup of coffee, the owner bypassed the valve plumbing, intending to get a replacement later in the day. Meanwhile, the gas could be turned on and off at the tank. When he turned the gas on at the tank, before his wife could light it, gas and boiling liquid propane started blowing out from various controls on the stove filling the boat with gas. Fortunately they lived to pass this story on.

Although very reliable, the pressure regulator can fail. If it does, high pressure liquid propane can be delivered to the appliance that is designed to take very low pressure gas. The important fact is the low pressure solenoid valve, either by brilliant design or by dumb luck, will not open under high pressure, so if you have a similar experience, check the regulator before bypassing that valve.



Siphons can sink a boat. A typical situation is a bilge pump which turns on when the water level operates the bilge pump switch. This pumps the water overboard and in the process, removes all the air from the pipe leading from the pump to the outlet. If the outlet is high enough above the waterline, when the pump stops air sucks back in the outlet as the water in the pipe drains back into the bilge. The only problem with this arrangement is some of the dirty bilge water dibbles down the topsides of your boat leaving a nasty stain. To reduce this problem, the outlets are often placed just above the waterline, or even below it so the discharge is out of sight. But now when the pump stops, there is no way for air to get back in the pipe and as the water drains out back into the bilge, seawater comes back in the outlet and your boat starts to sink. Even outlets just above the waterline can cause problems when the boat is heeling under sail, or has settled too low due to a leak, just when you need it the most.

So a siphon breaker is added at the highest point of the pipe running from the pump to the outlet. This is just an air valve which shuts under the pressure of water from the pump going out but opens and lets air in as soon as the pump stops.

Why siphon breakers fail.

Siphon breakers are notorious for not breaking a siphon. The reason is the valve is typically placed at the top of an inverted U pipe at the highest point. Every time the pump runs, the water shuts the valve but it also gets it wet with nasty salty oily gooey bilge water. After the siphon breaks, evaporation allows the liquid to evaporate and deposit a small amount of debris on the valve each time. Eventually it sticks closed and the boat sinks, or at least the bilge pump has to cycle continuously. The choice of materials for the valve is often poor, combining metals which corrode and rubber flaps which stiffen or rot.

The simple solution.

Siiphon.jpg - 1808 Bytes

Separate the valve from the liquid with a vertical pipe about 3 inches long which starts from the top of the U. Now when the pressure builds up from the pump starting, the valve closes and a small amount of air is trapped in the tube from the top of the inverted U up to the valve, keeping the valve dry. Any liquid which may creep up the tube a little runs back out when it turns off and air is admitted. With the valve remaining dry you can substitute a valve designed for air only. We recommend the Plast-O-Matic tubing valve, model PMMPC025SI-NY, which is all nylon construction with a Silicone diaphragm. It operates on very low pressure, seals bubble tight and can stand pressure cycles up to 40 psi. We supply a kit consisting of the valve, a short length of tubing, and a 1/4" NPT nylon hose barb if you have trouble locating one. Having obtained a reliable valve, there is no need to spend from $25 to $70 on a fancy "U" tube to mount it on - a couple of PVC hose barbs with some PVC fittings from your local hardware store will do the same for under $5.00. You will need a reducing bushing to go from the T fitting you use on the top to the 1/4" NPT hose barb which connects to the valve.


BubbleOut.jpg - 3779 Bytes

While on the subject of siphon breakers, above, let me introduce you to one of the handiest plumbing gadgets.

We have problems in a number of places underway where air bubbles come in via through hulls and collect enough to cause problems and allow pumps to lose prime. In particular, the Oil/Water separator on our RO watermaker collects air and eventually fills with air if you don't vent it manually. Often A/C raw water cooling systems will have a loop where air bubbles can collect and then get sucked into the pump when you start up next time, which make it lose prime.

We have put together this combination of valves that allows air out but blocks liquids. You can see the specifications at Trapped Air Extractor


It is not uncommon for centrifugal pumps to lose their prime while underway, especially if they are not running. Small bubbles entrained at the bow wave travel all the way under the hull and some accumulate in the inlet through-hull of the centrifugal pump, eventually accumulating enough to require re-priming.

First in will be necessary to turn the pump off for a short period of time with any technique to regain prime because the bubble of air in the centrifugal chamber will be stuck there while the pump is running. If it is running, the bubble can't "back out" because that would allow water into the pump from the outlet which immediately gets pumped out, sucking the bubble back in. Quite often in these conditions you can hear the pump oscillating back and forth as this happens.

For it to work, there must be a "high" point to which the air will rise when the pump is turned off. Depending on the orientation and shape of the pump chamber this may be just a high point on the inlet tubing, or quite often centrifugal pumps are fitted with a valve or screw-in stopper at the high point of the centrifugal chamber for priming purposes. If it has the latter this would be the best choice. The system must also be configured so air anywhere in the tubing, including the strainer, can rise to this highest point so the re-primed pump doesn't suck in another bubble from the strainer and lose prime again.

The simple solution then is to connect this high point to a riser tube, 1/2" or more in diameter that goes (more or less) vertically to at least a foot or two above the waterline. At the top end, where it is always dry, you connect a "normally open" solenoid valve. The valve (12VDC or 115AC to match the pump) is wired in parallel so it closes when the pump is running. The other side of the valve vents to atmosphere. Whenever you turn the pump off, any air rises under water pressure into this tube and bubbles out the top. When the pump is turned on, the valve closes to prevent water under pressure (or suction depending on where it is placed) passing through the vent tube. The stationary bubble at the top, between the waterline and the valve, keeps it isolated from the salt water so it only has to work in air and will be much more reliable. This means the valve can be a small 1/8" or 1/4" solenoid valve even though the vertical tube is 1/2" or 3/4" in diameter. This diameter is necessary since rising bubbles must pass through the standing water in the tube without forcing water up the tube which would slow or stop the venting process.

So whenever your pump loses prime you just turn it off for 30 seconds and turn it back on.

You can save the cost of the solenoid valve by pluming the top end to a convenient ball valve and operate it by hand - just open when the pump is OFF to release the bubbles of air.

TIP. If you are having trouble finding a 12 volt DC solenoid valve, the 24 volt AC valves sold by WW Grainger work just fine on 12 volt DC. See their Catalog Entry. You will need the valve for about $53.50 (Use the "Normally Open" port) and any of the 24V AC coils for about $20. They do show a 12 VDC coil but why pay $50++ when the cheap one will work?.

See the information at Pump Saver about preventing your centrifugal pump self destructing from over-heating if it runs too long without a prime.


First a WARNING:

NEVER connect a dock water supply to the pressure side of the water system on your boat. Not even with a pressure reducing valve. This is an invitation to sink your boat as I have witnessed it on two occasions. All you need is for one of those hose clamps to quit, or a flexible section to rupture and there is an unlimited supply of water to fill your boat. Far better to fill your water tank periodically using a hose and using the on-board water pressure pump to supply your requirements. Now if there is an accident, no more water can come on the boat than was already there and you can't sink. Keeping your pressure pump working on a regular basis is also better for it. Nothing kills pumps quicker than being idle for long periods.

And while on the subject, NEVER have a water tank that overflows anywhere on board. Plumb the overflow overboard or to a drain which always runs overboard because sooner or later you will go ashore and forget you left the hose filling the tank and your boat!

OK Now for saving water.

If you have ever been cruising, even with a water maker on board, you know how precious fresh water can be. On Yandina, with four heads, the run from the hot water heater to the aft head is about 60 feet of 3/4" pipe. By the time you run hot water back there for a shower, you have wasted over 3 gallons of water. This is proportional on smaller boats but still an unnecessary waste.

We installed a 12 volt solenoid at the far end of the hot water line and plumbed the outlet from this to a hose which returned to the water storage tank. Push button stations were installed at each place where hot water would be needed. Now you can dump the cold water back into your tank and use the hot water with a clear conscience. We got rather fancy with a relay and holding circuit which was broken by a thermostat monitoring the dump water so the whole process was automatic. Actually, a simple on/off switch at each station is all that is really necessary as it is unlikely you will forget and leave it on.

Do not use a PVC valve which can fail at the hot water temperatures. Also avoid valves with a pressure servo like the ones used on sprinkler systems because they often vent a little water and may not operate at boat water pressure. There is now a CONSTRUCTION ARTICLE with schematic and parts list.


Sucked some plastic or weeds into your through-hull strainer? Opened the strainer but it wasn't too bad? So the problem must be at the through-hull fitting itself. Hate to have to dive down to clear the inlet? Here is the solution:-

First some hints. The worst offenders are cooling water for air conditioners and refrigeration. They run long hours in summer, especially for cocktail boats at the dock, and suck in plastic, weeds, fish, and worst of all, barnacle and coral polyps of various kinds which set up house in your strainer. Hint #1. Keep the strainer in the dark - it discourages algae and some marine growth. Hint #2. Try to turn the system off for as long a period per day as possible in one session. While the water is not flowing, it stagnates and kills the infant shellfish before they can get established. Hint #3. Well this hint is only distantly related to the subject matter. ALWAYS turn off the device using the sea-water cooling when you are scrubbing the bottom. Even the tiniest pieces of copper bottom paint that get sucked into the strainer basket (if metal), will corrode it out in no time flat. (Don't ask me how I found that out.)

OK, here is the method (for centrifugal circulation pumps only). There is one snag (although the snag has some side benefits) and the snag is that the solution uses compressed air at about 80 to 100 lbs per square inch - more later - keep reading. I plumb in a Tee fitting just after the circulation pump outlet. On the Tee junction, plumb a ball valve (plastic or bronze only) and go to an air hose fitting (brass!). When the air conditioning or refrigeration cuts off due to over-pressure (= over-temperature), you do the following:-

  1. Turn off the device.
  2. Close the outlet through hull valve, leave the inlet valve open.
  3. Attach compressed air line to the new air hose fitting at water pump outlet.
  4. Open the ball valve on the Tee - WOOSH, the water in the pump and strainer is forced out under high pressure, taking everything with it.
  5. Close the Air Valve.
  6. Close the water Inlet Valve and open the water Outlet valve.
  7. Repeat the Air purge to blow out the lines going through the heat exchanger and to clear any debris from the outlet through hull.
  8. Open the Inlet Valve.
  9. Remove the air hose and open the air valve until water comes out to re-prime the pump. (Not always necessary but on some installations where the outlet is below water level, the pump won't self prime.)
  10. Close the Air valve and turn device back on. 60 seconds including getting the air hose!

This will not remove trapped debris in the strainer although it does remove mud, and dead fish. Sometimes I let the water back in the strainer and purge it a couple of times to flush out mud and goo. If the strainer needs cleaning, close both through hulls after both air purges and open the strainer for cleaning. Every boat should have a wet/dry shop vac which makes for quick and easy cleaning of the strainer and basket. On large vessels where the owner expects everything to be running all the time - plumb the compressed air to each strainer with PVC pipe and make a permanent installation.

A reader pointed out that PVC is not advisable for compressed air lines due to the explosive nature of a failure. He recommends as follows:- "Use of semi-rigid flexible plastic tubing works quite well as a substitute in this application as it is easy to string from place to place, uses common brass compression fittings, and is non corrosive. It will, of course, leak if damaged or excessively heated, but will not explode!"

For engine and generator cooling strainers where it is an impeller pump, the Tee needs to be placed just before the pump inlet so you can blow back through the strainer. You will not be able to blow through the heat exchanger. The outlet water valve should be left shut when purging so that no excess stress in put on the impeller blades.


How to make your own diving setup

Typical 2 HP Compressor

Select an OILLESS compressor with a suitable pressure tank and automatic pressure switch. They are readily available from places like WalMart, Home Depot etc., for $100 to $200 depending on size. For diving, the compressor should be at least 1 horsepower with a minimum output of 2.5 cubic feet per minute at 100 psi. Get a 2HP one if you want to dive with a buddy. The one pictured is 2.6 SCFM @ 90 PSI and should handle two divers. Unless it is a big boat with a genset, you are only going to be able to run it on shore power or I run mine for short dives from a 2KW inverter. Make sure you get one with a pressure shut-off switch. Some cheaper ones just run all the time with a safety valve that vents the excess and you don't want to be wasting that energy if you are running from an inverter.

You will need a water separator/air filter fitted to the output from the compressor if it doesn't come with one. They are about $20 to $30. Due to humidity on a boat, a water separator with an automatic drain is a good feature but not essential. For a more versatile and permanent installation, you can purchase a belt driven compressor to run off your engine. I ran permanently installed PVC schedule 40 pipe to an outlet in the cockpit to make connecting quick and easy. You will need a bunch of quick connect air couplings to make assembly and disassembly easy when diving. Always use the all brass couplings, the galvanized ones will only last about 7 minutes. Even the "all brass" female couplers use steel balls so rinse with fresh water and spray a little WD40 on them to keep them working. I use a 2HP Gast brand electric compressor that has maintained compressed air on my boat now for over 12 years with (virtually) no maintenance. The compressor should be bolted down so it doesn't move around while underway so remove the manual valve from under the air tank and plumb it to a ball valve to make draining water much easier. If you can plumb the outlet from the ball valve so it vents overboard it will be easier as it is hard to catch the water when it comes out under pressure. (How do I know that?)

You will need to purchase a "Hookah" type diving set that lets you dive to about 40 feet with a compressed air line tether to the boat. Check you local dive shop - the valve is not that expensive - it is made to work from the 80 to 100 lbs per square inch from the compressor, but otherwise it is just like a scuba valve. There are no tanks and it comes with a small harness that anchors the air line to your back. The dive shop may try to sell you a stainless pressure equalization tank that floats on the water surface to provide cooling and give you a small reserve if the compressor shuts down. You don't need this. Always use a long hose (40 ft minimum) for diving to provide cooling and you can hear the compressor from under the water so if it doesn't come on periodically you can head for the surface before the tank on the compressor runs out. I used regular neoprene style air hoses although some have reported problems using commercial air hoses so use with care or use the ones sold for diving.

I made float with a "DIVER DOWN" flag on it and terminated a (multiple) 50 foot air line at the float that came from the outlet in the cockpit. This line has a Tee and two couplings so you can plug in one or two diver lines. That way you can work in a radius around the boat and only use the final length of line for the vertical part of the dive which keeps a control on depth. The float also makes a great storage area for tools, fishing gear, and occasionally fish, out of the water for safety from predators.

You can't get into too much trouble if you restrict your diving to 30 feet but for your own benefit I strongly suggest you enroll in a scuba diving course and get your diving certificate. They teach you a lot more than the problems with nitrogen at depth, and the safety techniques are very important even at 6 feet under your boat.

A reader pointed out that there are significant dangers diving at 30 feet, in particular concerning rate of ascent. I can't stress the necessity too much of doing that diving class and getting certified for your OWN safety.

Another reader pointed out that PVC is not advisable for compressed air lines due to the explosive nature of a failure. He recommends as follows:- "Use of semi-rigid flexible plastic tubing works quite well as a substitute in this application as it is easy to string from place to place, uses common brass compression fittings, and is non corrosive. It will, of course, leak if damaged or excessively heated, but will not explode!"


Unfortunately mildew is a common problem on boats. Commercial mildew removers are expensive and have a limited life in storage. Apart from the obvious of keeping dry and ventilation, here are a couple of tips for combating mildew.


You will need to purchase some concentrate. I use AQUA CHEM spa care SHOCK TREATMENT. It is a white powder and the active ingredient is Lithium Hypochlorite, 29%. It is sold as a chlorinating shock treatment for spas and hot tubs and you will find it, or an equivalent, at any pool chemical supply. I purchased 16 ounces for $5.97 at Walmart. 16 ounces should supply enough mildew remover for approximately 50 years on a 71 foot boat!

Mix in the ratio of one level teaspoon of powder to one gallon of water. That teaspoon full doesn't look like it will be enough in that big gallon of water but don't be tempted to put more in - the powder is super concentrated and this ratio works very well. Since the label says it is a Federal offense to use this product other than indicated on the label, I suggest you take your boat out beyond the three mile limit before performing these illegal acts.

The solution should be kept in a sealed container, plastic bottles with a screw cap work well. Label well to avoid accidents. Transfer as required to a spray bottle but don't store it in the spray bottle since the air vent seems to allow the strength to weaken in a few days. Even in the sealed container it lasts only a few weeks but it is so cheap compared to commercial preparations - go ahead, make another gallon.

Don't dispose of excess solution or powder in the water unless extremely diluted as it is toxic to marine life. If left over solution gets too weak to use, I dilute it in my bilge and allow it to sit there exposed to the atmosphere for a few days before pumping overboard. So long as there is no oil in your bilge this helps keep your bilge clean and kills any smelly bacteria before emptying. I have a large bilge and plenty of ventilation, smaller boats might need to find an alternate disposal method but in small quantities it should not be worse than having an indoor spa.

On smooth surfaces - paint, vinyl, varnish etc., - spray on, leave a few seconds to work, and wipe off. You can even wet a paper towel and just wipe slowly and it will work. There is no need to rinse the surface, in fact I think the residue inhibits the re-growth of mildew. There is some chlorine smell so make sure you have plenty of ventilation.


Chemicals and scrubbing work fine on smooth surfaces but on halyards, dock lines, awnings, etc it is impossible to scrub down into all the cavities so a black residue is left which not only still looks dirty but is the seed for new algae to start growing.

The easiest way to get these looking like new is a pressure washer. You can do lines without removing or lay them down and move them a couple of times until you get all sides. It doesn't take much pressure and you may do some damage with a commercial high pressure unit so experiment with a pressure adjustment if there is one, or back off sufficiently so there is just enough pressure to remove the dirt and mildew. Just use plain water, you don't need to add any soap, detergent chlorine or Lithium Hypochlorite.


Most marine stores and catalogs sell a product called DI-GAS or MIL-DU-GAS and I have occasionally seen the equivalent in WalMart. These products are labeled "HAZARDOUS TO HUMANS AND DOMESTIC ANIMALS" and contain PARAFORMALDEHYDE. When not sold to the marine market these products are labeled "NOT FOR INDOOR USE". With the restricted ventilation in boats this warning should be more applicable! CAUTION, they are quite nasty, in fact, if you use it as instructed you boat will become uninhabitable. DO NOT USE AS INSTRUCTED.

Despite the above warnings against these products, they do work well to prevent mildew and the "boat odors" in closets etc. Use these products by opening the seal as instructed but then enclosing them in a zip lock plastic bag. Cut a " hole high in the side of the bag and hang in your closet. The reduced dissipation is still sufficient to prevent mildew and the bag of poison lasts a year or more instead of a couple of months. This works well for enclosed spaces but I do not recommend trying to control mildew by treating the whole boat space, unless the boat is unoccupied for an extended time.


WARNING: If you are not familiar with 115 volt electrical wiring techniques you should have this work performed by a qualified installer.

Many larger boats that have 115volts AC available from shore, generator or inverter, use a traditional domestic well pump for pressurized water. These pumps have the advantage of being cheap and readily available however they suffer from one serious problem, especially on a boat where the water tank can run dry. The impeller in them is usually made of plastic and if the pump continues to run when dry it will overheat, melt the impeller and self destruct.

One solution is to use a pressure switch which has a low pressure shut-off. So long as the pressure remains above about 5 pounds, the switch operates normally but once the pressure drops too low (usually due to running out of water), the switch cuts off and must be reset manually.

But this is only a partial solution and is usually not reliable because there is usually enough pressure in the the pressure tank to hold the switch on even though the pump is running, trying to build pressure up to the high cut-off, but failing due to lack of water. Well here is the trick. Remove the thermostat from an old abandoned water heater, or if necessary purchase the cheapest one you can find (usually under $10). Set the temperature to the lowest setting. Mount it so the rear is flush on the body of the pump (cable ties, epoxy etc.) and wire it in series with the supply to the pump motor. I covered it with a PVC junction box to provide protection from the exposed wiring. Now when the pump starts to overheat, but long before it gets hot enough to self-destruct, the thermostat shuts it off until it cools down again.


I was greatly impressed with the way my friend made a Union Jack flag:-

Purchase a full size piece of fabric in each of the colors you are going to need and trim them all to the outline dimensions of the flag plus about 4 inches. She used the ripstop type sail cloth although the reds faded quite rapidly with this material.

Lay the pieces on top of each other in any order and stitch around the outer edge to hold them all together, perfectly flat.

Then using a grid layout, an old flag or your favorite method, reproduce the complete artwork of the flag on an outer surface, with a fabric marker, leaving at least 2 inches outside the drawing to the edge of the material on all 4 sides.

Next take the sewing machine and stitch along all the lines you drew, which will later become a seam where the color changes. On a larger flag you can run two lines of stitches very close to each other for extra strength.

Now using the original picture or flag as a guide, remove all the wrong colors from each bounded area with a pair of scissors. Cut from both sides as necessary until you reach the desired color. Leave a small seam edge to the sewn line to prevent unravelling. Depending on the material this could be as small as 1/16 inch, or up to 1/4 inch on larger flags.

Finally, remove the original outer stitching and make an outer fold-over seam around the outer fabric.

Doing it this way keeps everything flat, no messing with up to dozens of little strips of cloth that you forget where they go, no sticky tape to mess with and remove later, and no stretching or trimming trying to get all those seam allowances to fit.


Anchoring where the tide shifts 180 degrees, (up to 8 times a day where we dock) can risk pulling your anchor out with the repeated changes and can twist your chain or rode up. In particular, if you put out 2 anchors like the Bahamian method, the rodes twist up making recovery difficult if not impossible, especially with 1/2" chain exiting from hawser pipes.

So here is how we do it. These instructions apply to our 71 ft, 75 ton steel ketch where the Danforth anchor weighs 165 lbs and the Bruce 130. Smaller boats can accomplish the following in a similar manner.

1. Head upstream and drop and set your first anchor.

2. Pay the chain out as far as as you can as you back down with the tide or under power if necessary.

3. Drop the second anchor and leave the chain loose.

4. Winch in on the first anchor about 25% of the length out.

5. Attach a line and chain hook to the second anchor rode and keep some tension on it.

6. Winch in on the first one another 25% of the length while walking the attached line along the side to the aft end and allowing more chain to pass out on the second anchor.

7. Winch in another 25% on the first while holding some tension on the second with the attached line and an aft cleat, then cleat it off.

You are now anchored fore and aft. If the forward one is all chain, you should put a 3 strand nylon snubber on it.


I use the clear 2 part awlgrip polyurethane for varnishing so I often need small batches from larger containers. It makes a long lasting, hard surface brightwork job with just 3 coats, but it doesn't go well over conventional varnish - it has a tendency to bubble. It may not look as good as a fresh conventional varnish job but averaged over the 2 years (or more) I go between refinishing, the AVERAGE appearance over the period is far superior.

The polyurethane mixing ratios are usually not 1:1 so you need to take a tongue depressor type stirrer and mark the depth on it that you think you need - (which can only come from experience) - with a ball point pen. Divide the space below it with a second line in the ratio of the mix, and add a third line above it for the 10% or ?% of brushing thinner that you need. Since it always runs out when you have just a little more to do, the extra % from the thinner will get you through the job (Yeah, right).

In really hot weather I give the mix a head start by cooling the components in the refrigerator before dispensing, and avoid leaving the mix in the sun while using it.

Pour each of the components in slowly to avoid bubbles so each reaches the next mark on the stirrer held vertically in your mixing pail. Have paper towels handy and wipe the screw tops and caps very thoroughly before replacing them. Then stir gently but thoroughly. The manufacturers say to wait 15 minutes after mixing before using and although I usually do this, however I have not had any problems when I skipped it.

When painting with a brush, draw paint from one side of the container, but wipe the brush out on the other side so the bubbles have to traverse the width before getting to your brush.


The combination of urine in salt sea water causes the calcium to be released from solution and deposited in your plumbing. If you are cruising in sea water, and fresh water is precious, Pipe.jpg - 4285 Bytesyou do not have much choice and the only preventive measure is to flush copiously until there is not only fresh seawater remaining in the pipes but the pipe walls have been flushed clean. We're talking gallons of sea water, not 10 strokes on the pump. With inadequate flushing, a 2" PVC pipe can be reduced to a 1 inch cavity in just a few months. If you carry any muriatic acid (which you probably shouldn't on a boat), an ounce added to the last flush once per week can help reduce build-up. To make cleaning sewer pipes easy, do not use glued joints. Purchase a rubber sleeve for each elbow or joint and use two hose clamps to make the joints. You can purchase rubber elbows which can attach the same way. Now disassembly and cleaning will be much easier.

When you are at a dock, however, flushing with fresh water is the best solution (literally). Ideally you should place a "Y" valve in the input line to the head. One side of the "Y" connects to your sea water supply, the other to a line connecting to your fresh water tank through a one-way check valve so water can only pass from the tank to the head. It should be a direct connection to the tank itself. Avoid Teeing off the line going to your fresh water pump which may produce a negative pressure at the check valve which would make flushing difficult when the pump is running and may allow water to pass the wrong way by the check valve if it does not seat perfectly. All flushing water lines to the head should have a siphon breaker in them above the water line to prevent siphoning in or out of the head, especially if connected as above to the potable water system. This can be placed between the water pressure pump and the head connection. Where the pump is attached, the line may go down and up into a bulkhead cavity to keep it out of sight, so long as the siphon breaker is at the highest point and above the water line of both the seawater and the freshwater tank. See our article on siphon breakers after finishing here.

SAFETY WARNING: Siphon breakers and check valves are notoriously unreliable. Despite the very good reliability of our siphon breakers, and the use of a good quality check valve in fresh water, if they should both happen to fail there is the possibility of siphoning water back from the rim of the toilet into the potable water. Unnamed experienced sanitation aficionado persons (UnESAPs) recommend doubling up on these items to give an extra margin of safety. You should judge the necessity of this for your installation. If they should fail, the functioning of the flush should be obvious to an experienced user since the bowl would remain completely dry instead of having the water from the rim and pipe up to the siphon breaker fill it at the bottom after each flush. However if you allow strangers to use your boat they might not notice such a subtle change.

The Y valve should be selected to make sure the sea water side shuts off before the fresh water side opens as the valve is operated. With the difficulty I had finding a suitable valve, and the traditional unreliability of marine Y valves, I opted for two PVC ball valves and a sign warning that the sea water should be shut off before the fresh water was turned on.

Another solution is to provide a lever operated ball valve from your pressurized water system that Tees into the flush line going to the head. Again it is important to have a siphon breaker so water could never go the wrong way from the head if your pressure system was not working.