Brian;
With advice from Don Casey's book, I built the following system.
Attach a small pump (500 GPH) to a float switch and use a really small hose (1/2 inch). The intent of this pump is to pump out rainwater, any water you pick up with aggresive sailing, etc. The benefit of the small hose is that when the float switch finally shuts off, the water in the hose drains back into the bilge - but there is not very much and it easily evaporates.
In the case of an emergency, mount a 2000 GPH (or larger) pump to a much larger hose (1.5 inch) with it's float switch higher in the boat than the small pump's switch. It will only run when the small pump is overcome or fails.
I had an emergency last year where the little pump could not keep up with the leak. The big one saved the boat while I made it to to boatyard for a quick hauling.
I used Rule equipment and it worked exactly as planned.
One annoying note - I did install one of those switches that is "off-auto-momentary on". My intent is to leave it in "auto" all the time, but occasionally it gets switched to "off" unintentionally with the annoying side effect of a wet bilge.
I hope this helps.
-Steve