Our Kingscraft has a diaphram type sump pump. The PO told me this was so it could such up the last bit of water. This weekend I got to the boat to find about a foot of water in here (different thread) so had an opportunity to use the pump. It seemed to pump VERY slow. I know there was a problem with the strainer (leaky gasket and stripped screw) but even when I sealed it up with waterproof elecrical tape (the stuff kind of like a rubber caulk) it didn't seem to pump very well.

Are these pumps worth repairing and using, or should I just replace with a different type pump? For those not familiar with the Kingscraft, there is a "V" in the bottom where the water collects, and the standard rotary type pump you get at Bass Pro Shop won't get the last inch or so out of the boat.

Diaphram pumps are slow, unless they have a VERY large diameter. The centrifugal type moves a lot more water. I look at bilge pumps as if you'd should never need them - fix the leaks first and should the unexpected happen - like blowing a hose - the pump helps out. I would sponge or wet vac the remaining - in the rare occasion you should get water in the hull.

This pump has a 3/4 inch ID hose, though I don't know the flow.

The water was from the clean water system (a drip in the line to the pump, dripping for 2 weeks), so the leak is fixed pretty quick and easy. The problem with the centrifugal pumps, at least the ones I've seen around, is that they won't get down into the "V" of the hull. Even vacuuming isn't working great because I suck out the area I can get to and it takes a while for the water in the areas I can't get to to run down. I think I make just need to stuff a bunch of old clothes down there some weekend and pull them out the next.

I did pull the strainer last weekend to see it I could either fix it or find a replacement and found a bunch of stuff plugging the inlet to the strainer. I'm guessing that was at least part of the problem. Hopefully when I get the air leaks in the strainer fixed it will work better.

Looking at the way the previous owner had the water tanks set up, I think he probably added a few quarts of water every time he filled the water tanks. He also had just replaced the water pump on the engine, so he might have been having to empty the bilge from that also.

I guess I could get a centifugal pump with an auto switch and put in in in case of emergencies (the current pump is manual only) and to pump high volumes and keep the diaphram to try and suck up the last bit. I just hat drilling holes in a boat hull. It just seems wrong some how.