If you're only using it for small jobs around the boat, why not get the smallest (usually 1 gallon) wet-dry vac they have at Wal-Mart or Target. I have one in the garage for small jobs, like vacuuming out the cars, and works just fine, even on pet hair. They're small, compact, relatively powerful, and they're only $20-30. Use it until it dies, then pitch it overboard.
(I'm just kidding about throwing it overboard. Don't do that. Do as I say, not as I do.)