The typical through the deck bilge
pumps are just toys. They don't move enough water
to put a dent in even a small leak. Really only useful to pump the bilge from nuisance deck leaks
Whale makes a great pump that is easy to clean, trash is the cause of most pump failures, and moves a lot of water. Negative is it is expensive and fairly tall so hard to find an unobtrusive place to mount it. Can be mounted on a board and deployed when needed, but once again, takes up a bit of space in a locker.
I have the Edson pump mounted on a board. The low profile makes it relatively easy to to store in a locker. It will move a lot of water quickly. Filled my relatively deep bilge to the floor boards when a torrential down pour caught us in the boatyard with all the hardware
and hatches removed. Only took a few minutes to empty and wasn't tiring. New, they are very expensive. Got mine at Blue Pelican 2nd hand store for a third of new cost. They were common on commercial
boats and turned up regularly. There is also a guy who is selling the aluminum
variety at a good price
. He's posted notices on this site. A search of the archives
should lead you to him.