Hi there. Try this site for some relevant discussion:

http://usrwww.mpx.com.au/~pcarter/pumps.html

I think it's the site Pete Rudie was referring to (he gave it to me after a similar conversation). After some practice sessions of my own with a small handheld pump, it became clear to me something else was needed: You can't paddle while pumping with them, and they are somewhat exhausting to use for the amount of water that gets in my cockpit.

I was getting hung up on trying to design my own foot-operated pump, but maybe this is the way to go. I've seen similar pumps at West Marine in the $40 to $50 range that I think could be adapted to this use.

They also have a small submersible electric pump. It's good for 5 to 6 gallons per minute at 2.4 amps at 12 VDC. Only problem (aside from waterproofing against salt water) is that the only battery I have capable of running it for more than a few minutes is a 7 amp-hour rechargable unit that weighes 6 pounds, which I think is on the heavy side. I think the foot pumps weigh less than half that.