Question:

[Destroyer]

Originally Posted by mawshj

the theory is that the vanes act as a positive displacement pump at low speeds and flex more and more as speed increases there by regulating water pressure so to protect gaskets and hoses. also allows sand to flow thru . at w.o.t. the vanes do not touch the outer pump housing but act as a turbine pump. I do not know if it really works that way but that's what I was told by O M C man.

I'm a mechanical engineer by trade.. (or at least I was until I retired a few years back) What you were told by the OMC man is correct as far as how they operate in principal. I've never questioned that. All I'm asking is is there anything else that might work instead.

And by the way, to point out to everyone else, a turbine pump is, in fact, a form of centrifugal pump in that the blades do not touch the outside of the pump body at higher rpm speeds.. so all the arguments about them passing sand and debris etc. fall exactly into the same category as a centrifugal pump. They both will do the same thing, in the same manner. It is only when the pump is operating at lower speed that it acts as a positive displacement pump... and that is exactly what the lower speed British Seagull outboards do with their centrifugal pumps. So if a centrifugal pump can operate at low speed and provide enough cooling, and a turbine style pump can operate at higher speed, why not combine them into something that does both jobs and isn't made of a material that can self-destruct if run without water in less than 20 seconds.