Quote:
Originally Posted by THEFERMANATOR
Contrary to what you might think, higher head pressures CAN cause problems inside the engine. The gaskets and such for the cooling system would have to be completely re engineered to handle pressures in excess of 20 PSI. The only sealing surfaces meant to hold higher pressures are the sealing ring for the head gasket in the cylinder area only. Also higher pressures can have a negative effect on cylinder liners not only from abrasion, theres also cavitation, and micro bubbling at the cylinder liners from the engines combustion process. You are going to get micro hot spots which form tiny air bubbles along the cylinders in the cooling jackets, and these air bubbles under pressure can act like a snad blaster when a combustion event occurs. It is like a hammering action when the cylinder fires, and that hammering action acts upon the cylinder wall in the cooling jacket. As pressures increase, this event is worsened. Believe me, there have been attempts at finding something better, but if it existed don't you think somebody would have come out with it by now. The engines you are talking about with hard impellers osund more like tender engines used on non planing hulls where ingesting air at speed, high RPM useage, and other factors are not a concern, hence why they can use what they use.
And engineers have come up with a pump that can do multiple applications, it just so happens to be the rubber impeller that has proven itself for over a century now.
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Ok, I'll go along with what you say as far as the re-engineering of various gaskets to take a higher pressure. So you'd have to use an automotive type of gasket. (Or some kind of pressure regulator elsewhere in the engine) But the cavitation and micro bubbling you speak of I have my doubts about. After all, you would have the same effects in a car, and I don't recall ever reading about it in and of my shop manuals.
You are spot on about the seagulls.. they are low speed engines for sailboats and other non-planing hulls. Still not convinced about the rubber impeller though.
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1987 V20 w/1987 150HP Yamaha on a Shoreland'r Trailer
1978 16.5 Airslot w/1996 120HP Force on a Four Winns trailer
1996 V21 w/1993 200HP Mercury on a Shoreline Trailer
All towed by a 5.7L Hemi Durango.
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