> I can squeeze the pump with my hand fairly easily. I also squeezed my
> bathroom scale to what I thought was the same pressure and came up with
> 25-30 lbs.

Well, uh, I may be wrong, but I had this theory, see... .

Using Roszyk Math, I calculated that in order for a Guzzler pump to lift the advertised 12' on the suction side, it would need to generate a 5.2 psi differential. With a 3" diameter pumping diaphragm (7 sq in), this translates into a 36 lb force, which the spring "generates". Or rather, you do when you compress the spring with each stroke. The spring stores the energy,then releases it on the suction stroke.

As we need only a 1' lift, I was contending the spring likewise could be weaker and still do the job: a 3 lb. spring as opposed to a 36 lb. Thus 90% of the effort was wasted with every stroke. Seemed like a waste in a situation where conservation of energy was a good idea.

I gave Guzzler/Bosworth a call, but the official spring compression strength was not at their fingertips. By the way, that duckbill valve isn't available for the 400 series.

> Another thought: If the spring were "just right" wouldn't that
> make the flow almost zero.

I don't think so. If the spring is too weak, it won't draw water into the pump body. If it's too strong, the stronger it is, the more energy is wasted in compressing the spring for work that does not help empty the cockpit. If it's just right, the force of compression would match the suction side requirement and no more.

In a kayak, with the pump mounted low, water in a filled cockpit will want to flow into the pump until the cockpit water level drops below the the pump body. You wouldn't even need a spring until then, but I'm ignoring this for the moment.

> It seems to me that a stronger spring gives
> higher water flow rate. This sounds better when pumping out a boat as long
> as the spring isn't so strong that it affects how fast you can compress
> it.

A stronger spring will refill the pump body more quickly than a very weak spring, given the same system. This may be where I'm going wrong, as I'm not calculating time (horsepower) requirements. We want to pump quickly, so if we have to wait for the weaker spring to push out the diaphragm, then that's no good. I'm trying to optimize, that's all.

BTW, I still like the bungee thing. Without the spring inside, the pump can be left in the final discharge position. That saves me a couple of inches of precious foot room.

Thanks for checking it out for me. Guzzler also gave me another number: 1-888-438-1110.