[Destroyer]

Originally Posted by THEFERMANATOR

Rubber impellers are used because the yare self priming by nature, and are forgiving to debris going through them like sand, and provide good output at low RPM's. There are other optons, but the rubber impeller is still the best overall option for reliability, longevity, and durability.

Ferm, I know that you know your stuff, and everything you said it true,
but just for the sake of arguement, let me put forth the following. Both of my Seagulls pump a ton of water when they run. One is a 2 1/2hp and the other is a 4hp. Both have solid impellers similar to the kind found on just about any pedestal sump pump. I have a pedestal sump pump, and looking at it I find I was wrong, it's a 1/2hp motor, not the 3/4 I thought it was. Regardless, it still pumps to a 25 foot head. At 3 feet of head it will pump about 4000 gph. According to it's specs, it's designed to pass up to 3/8" solid debris, which is far more than any rubber impeller will.
You say that rubber impellers are self priming by nature, but if submerged, so is a pedestal pump. You would probably have to redesign the lower unit a little to get the pump impeller under the water intake ports, but other than that the self priming feature is pretty much a wash.
As stated above, the solid impeller will pass debris like sand and seaweed about the same as a rubber unit... perhaps a little better. Finally, my pedestal pump impeller is direct coupled to the motor via a shaft, turns at 1725 rpms and pumps 4400gph at zero head. That's a lot of cooling water at idle speed.

I know that this is all just conjecture, but it would seem to me that there's really no good reason to not use a solid impeller, especially given the fact that the British Seagull engines, (considered by many to be the best, most reliable small outboard engine ever built), use a solid impeller in their design. Really, I cannot see why they could not be used on larger engines. I wish some engineer could give me some hard facts documentation as to why the rubber impellers are used. (Other than the fact that it's just good business to make a unit that needs yearly replacement at about $35 per unit)... Multiply that by how many hundreds of thousands of outboards in use and that's really big business.