Dewatering Equipment for Offshore Sailing

Dewatering Equipment for Offshore Boats

Offshore boats must be prepared to handle a major flooding problem. Most electric bilge pumps will be of little use when there is a hole in the boat. High capacity manual pumps and/or engine driven pumps will be required to move large amounts of water from the boat.

This topic covers dewatering equipment for offshore boats that may be days from outside help.

Keeping Tabs on the Bilge

Most boats are not equipped with a high-water alarm. Without an alarm, your first indication that there is a problem will be floating floorboards. It's easy and inexpensive to install a float switch and an audible alarm signal. You may also wish to include a warning light at the helm in addition to the audible alarm. Set the float switch about 6" above the normal level of water in the bilge. Test the high-water alarm on a regular basis.

Another useful monitor is a bilge pump cycle counter.

Dealing With Offshore Flooding

Once the alarm alerts you to a problem, your first action should be to switch on the electric pumps, if not already on, then find the source of the problem. Unless you've hit a reef or rock, two of the most likely sources of flooding (according to a BOAT/US report) are leaks at through-hulls, or leaks at the raw-water cooling system.

It's critical to quickly isolate the problem and stop the flooding. Consider the rate at which a hole in your boat will admit sea water. If, for example, your 1 1/2" diameter transducer for the depth sounder is damaged, and the transducer is only 2' below the waterline, water will rush into your boat at a rate of 88 gallons per minute (over 5300 gallons per hour!). There are no manual or electric pumps that can keep up with this flow rate. They'll handle part of the problem while you find the hole but you must reduce flooding to a rate that your pumps can handle. See the related topic on tools and supplies for damage control.

Once the hole is found and patched, your pumps will dewater the boat and keep up with any residual flow of water until you can make it back into port.

Electric Pumps

The electric bilge pumps in most boats can be counted on to move only a moderate amount of water. Manufacturer's claims for gallons per hour of water moved are grossly overstated, and your real-world performance will be much less than they claim. A good review of bilge pumps can be found in this comparative report from PowerBoatReports.com.

See the section on 5 tips for a better bilge pump system for ideas on making your electric bilge pumps as effective as possible.

Engine Driven Pumps

Engine driven pumps can move a substantial amount of water in a short time. If you have sufficient space in your engine compartment, you may be able to mount a belt-driven pump on the front of the engine. Most boats have room for a shaft-driven pump such as the Ericson safety pump. These are the only pumps that will keep your boat afloat if you can't stop the source of flooding.

One option available to everyone is to put a Y-valve on the raw water intake hose between the seacock and strainer. Closing the seacock and switching the Y-valve allows you do pump bilge water out of the boat through your engine.

Manual Bilge Pumps

There's an old saying that "the best bilge pump is a scared sailor with a bucket. All offshore boats should carry at least two buckets and a simple, sturdy manual bilge pump. These pumps will keep working when electric pumps fail. A high-capacity manual pump with a long handle, like those made by Edson, can be relied on to move large amounts of water from the boat.

Maintenance and Clog Prevention

Here are a few tips for making sure that your bilge pumps will work when you need them most:

Keep your bilge clean of debris. Rinse it out thoroughly twice a season.
Clear out the "limber holes" that let water flow between bilge compartments.
Make sure bilge pump wires are not sitting in standing water. Wires will quickly corrode if they are in water.

Dewatering Equipment - Inshore Sailing

	Item	Link to Detail
Automatic Pumps
	Electric bilge pump of sufficient capacity to clear the bilge in a reasonable time
	Smooth bore hose with no check valves or other obstructions. Anti-siphon loop extends above the waterline when the boat is heeled.
	High-water alarm in bilge - set for 6" above bilge pump trigger level (optional)
	Wired directly to batteries through a circuit breaker; won't turn off when you turn off your master battery switch
Manual Pumps
	Buckets (at least two)
	Manual bilge pump (permanent mount)
	High capacity emergency manual pump, hoses, strainer, spare handle

Links to Outside Resources

	Item	Link to Detail
How-to Articles
	How to install a bilge pump system; different types of bilge pumps.	Link
	Test reports: 20 different bilge pumps compared	Link
	Basics of Installing a bilge pump from BOAT/US	Link

Manufacturers
	Ericson engine-driven emergency pumps	Link

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