Hey Doug, What about the oversized racquetball-type balls used for "Wallyball". (Volleyball played in a racquetball court). They might have enough memory.

I think for me it would be worth the hassle of fixing a spring inside the pump, rather than hoping a ball has enough memory to pull water in. Of course, if I install the ball only and it doesn't work well enough, I can always add a spring later.

For a spring mount, I was thinking of a 1/2" to 3/4" rubber disc, sized slightly larger than the ID of the spring. Use some good quality rubber adhesive (like Aquaseal) and glue it to the center of the inside of the ball. The spring could then be forced over the rubber disc to keep it permanently indexed at the center of the ball. A similar wood or rubber disc could be mounted to the bulkhead/forward end of the pump chamber. I should check the prices of a suitable SS spring to see whether it's economically feasible, or if I should be searching for a "memory ball"!

: That would work reliably and be large volume. If a basket ball is 12 inches
: in diameter and half of it were used the volume would be about 450 cubic
: inches. That's about 9 times the volume (per stroke) of the hand pumps
: I've used!

Nearly 2 gallons per stroke would be awesome, wouldn't it!?!? We'd probably need a large enough valve body to allow that much water to flow through in 2-4 seconds. I wouldn't want a stroke time much larger than that.

I was thinking about an 8" ball (like anyone else cares!) but half that ball would give us a mere 135 cubic inches, or 0.6 gallons, which is still almost 3x better than a hand pump, and probably 5-6x better than the "average" foot pump. Let's see, if you could pump 0.6 gallons at 1 cycle every 3 seconds, you would pump nearly 12 gpm, and 700 gph, which is faster than some small electric pumps.

With a 2" deep pump body, the whole pump could protrude as little as 1.5" into the cockpit, and you could expel most of the volume of a hemisphere with each pump (figuring that you won't squash the ball completely flat, yet you will push slightly into the pump body.

: Your solution is better I think!

Thanks, but I can't take ownership of the whole solution! You and Tim get credit too, ain't brainstorming great!?

Shawn