The technician at Amel in Le Marin (the fellow that used to work with Jean Collin, has been there a while) talked me into buying a spare pump last year. The new pump looks nearly identical to the old one, same manufacturer. I have not used it yet.
We are currently cruising full time and the original pump gets a fair bit of run time. It runs for about 15 -30 seconds to drain the gray water sump. I'm not sure which Amel supplied pump you have, but the one that came with my SM (#37) has been good, except for the suction flapper valve becoming misaligned...which I finally fixed with a modification....don't tell Bill R.
Anyway the pump that came with my hull seems to be reliable, you might want to see if this version would fit with your layout.
Oh and Bill K is right, centrifugal pumps are sensitive to crud in the water. I would not rely on one as the primary water mover.
about to sail out of St. Augustine.
I have to say that at first I wasn't too impressed with the 'un-Amel' solution that was installed on Adagio when we got it, but after further review I believe it was a good decision on the part of the P.O.
The original pump has been replaced by a 24v Whale Gusher diaphragm mounted about a meter above the full water level. The hose from the pump run straight down into the sump and has check (standard joker) valves both before and after the pump to prevent loss of prime. I installed new jokers in Feb., 2014 and have not had a lick of trouble since. The pump is easily accessible, a rebuild kit is readily available (although I haven't had to rebuild it yet) and it's 'relatively' inexpensive.
It probably isn't a fast to pump the bilge as the original one (takes a full minute or so) but it's quiet and I've kind of grown into liking it. Just my 2 cents worth on this kind of project.
SM 209 Adagio