All About Bilge Pumps
Those Essential Devices for Keeping Your Boat Off the Bottom
by David H. Pascoe, Marine surveyor
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Emergency Pumps - Who Should Have Them and Why
"It can't happen to me." That's the attitude. Just as people head out to sea without a life raft, so do they go cruising without a high capacity emergency pump in the event something goes wrong. But it can happen, and it does happen, to all those good folks who thought they'd never need it. Every time you head out, the odds increase that it will happen.
Anyone who does any long range cruising should have an emergency bilge pump. No, I'm not talking about one of those hand pumps. Anyone who's ever tried to work a hand pump for five minutes knows that these things won't do. Even a man in good physical condition can not operate one of these things for very long. A typical disaster that could have been prevented by an emergency pump is the loss of a propeller shaft or a rudder, which opens up a hole just large enough that ordinary bilge pumps can't handle. That's where an engine driven pump can save your boat and your life. If you're going cruising, you should have one. Period.
Yes, they are expensive to install, but they can be MORE valuable than life rafts or life jackets because it may obviate the need to ever use these things. The idea is to keep you from having to abandon your sinking boat. Engine driven pumps are very high capacity with the volume being controlled by engine speed. They are more reliable than electric pumps because they're mechanical. The average size pump runs about 50 - 65 gallons per MINUTE, and that's a lot. An honest 3000 GPH, a capacity that can deal with some serious hull flooding.
For smaller sailboats, installing one can be more difficult because there's no space at the front of the engine. The solution is to add a pulley to the propeller shaft and drive it from there. It has to be operated with the engine in gear, but it will still do the job. You may be able to find a split pulley (in 2 halves) that will make installation a lot easier. Instead of having to remove the coupling, all you have to do is drill a slight detent hole.
Shown in the photo below is another good option, a suction taken off from the main engine pumps. It's a whole lot cheaper, but the only draw back to this arrangement is that if you run the engine pump dry, you burn up the impeller and now you've got another problem. This arrangement is a lot cheaper than adding a belt driven pump, but if you go this route, make sure that you understand what you have to do to operate it without wrecking the engine. It takes two people. Also make sure the T-off is BEFORE the sea strainer so that you're not sucking up bilge debris into the engine.
Okay, we've covered just about everything with the pumping system except the power source. For larger boats with big batteries, this is rarely a problem. It's a huge problem for small boats where all the builder saw fit to provide were an el cheapo car battery or two. I don't care that it says MARINE on the side of it, it you've got those brightly colored, thin casing plastic batteries, it's not a marine battery. I don't care if it says "deep cycle" or that it can light up the universe, I've yet to see one that isn't a piece of junk. My auto mechanic tells me the same thing; the average car owner is replacing batteries every two years because they are junk, junk, junk. Just a big sales racket.
If you want to save bucks by using cheap car batteries in your boat, you've wasted your time reading this because your pumping system is no better than the batteries that run it. Batteries die, pumps die. Here's the deal: as batteries age, the amount of charge they hold begins to drop dramatically. Two 14 amp pumps equals 28 amps, and wired to a common 60 ampere hour battery means that the two pumps would theoretically exhaust a new battery in two hours. But it never works out that way because as the battery declines, it's ability to provide power declines at an accelerating rate. When the battery is older, the problem is even worse. The average one year old 60 AH battery will barely run a 14 amp pump for 30 minutes. And if you have to pump that water uphill, it gets even less than that because the pump is straining at maximum current draw.
Do you get the picture? Take it from someone who has screwed around with cheap batteries most of his life, it is not worth fooling with those things. Go for a heavy duty commercial or marine battery. Surette, American, Exide, any of the big battery makers. You can tell if it's for real if it's big, black, very heavy and costs twice as much. Good batteries are heavier because they have more lead, for one thing. You are better off with one size 8D battery than you are with two smaller, cheap ones. Capacity is DIRECTLY related to size. Paring up two small ones is no match for one large one. An 8D (250 AH) costs about $250.00; two 90 AH auto batteries are going to cost around $100 each, so the cost isn't that much more. A pair of 4D (125AH) will work nearly as well.
The common mistake in wiring pumps is to wire them after the shutoff switch or the main circuit breaker on the panel. It happens often that someone turns off the main power without realizing that he is also shutting of the bilge pumps. To test whether your boat is wired wrong (and many are) turn all the power off and then test the pump by lifting the float switch. If it doesn't go on, then you know what the problem is.
I do not agree with the ABYC standard that bilge pumps must have circuit protection. Far too often, the circuit breaker or fuse is the cause of a boat sinking. If you want to eliminate circuit protection, try to keep the wire run as short as possible. While it's not good practice to wire anything direct to the battery, I'd say the lone exception would be bilge pumps. If there's no other practical way, go ahead and do it. This applies to submersible pumps only. These pumps have no history of burning up and starting fires.
When adding pumps, the easiest way is to purchase the small Rule three-way switch panel which has an indicator light too. Where to find a power source can be one of the more difficult tasks, especially if you're adding a pump up forward. Don't make the mistake of tapping off some other equipment or bus. Take the time to string the wire right. Your options are to go to the main panel, direct to the battery, or from the terminals on the back of the battery switch, making sure that you get the one that's always energized. In most cases, going direct to the battery will be easiest.
No doubt someone will send me an e-mail saying "How dare you recommend violating the rules," but I am not telling you that you must go to the main panel because with many panels that is nearly impossible to do.
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- What Makes for an Adequate System?
- Evaluate the Number of Compartments
- Determining the Number of Pumps
- Outboards and Stern Drives
- Capacity of Pumps
- What Brand?
- Pump Installation
- Float Switches
- Open Versus Covered Switches
- Doing It the Right Way
- The Discharge Outlet
- Emergency Pumps - Who Should Have Them and Why
- Battery Power
- Wiring Pumps
Posted November 10, 1998 (First posted 6/10/98 at www.yachtsurvey.com. Page design changed for this site.)