Question:

[THEFERMANATOR]

Originally Posted by Destroyer

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.

The micro bubbling is more an issue with diesels due to the higher cylinder pressures, but it is present in gas engines as well. Do a search on INTERNATIONAL 7.3's(not the powerstroke, but the IDI version), and you will find plenty of problems with cavitation and cylinder erosion due to the micro bubbling and it's effects. As pressure increases, the effects are normally worsened. Outboards already use automotive grade gaskets or better. Most automotive engines rarely see more than 16-18 PSI whereas in an outboard that is common pressures, and 20-25 can be seen. I understand your thinking, but your over thinking it. I know many think they can build a better mouse trap, but i nthe end the tried and proven design normally wins out. This is one of those situations.

[Destroyer]

Originally Posted by THEFERMANATOR

The micro bubbling is more an issue with diesels due to the higher cylinder pressures, but it is present in gas engines as well. Do a search on INTERNATIONAL 7.3's(not the powerstroke, but the IDI version), and you will find plenty of problems with cavitation and cylinder erosion due to the micro bubbling and it's effects. As pressure increases, the effects are normally worsened. Outboards already use automotive grade gaskets or better. Most automotive engines rarely see more than 16-18 PSI whereas in an outboard that is common pressures, and 20-25 can be seen. I understand your thinking, but your over thinking it. I know many think they can build a better mouse trap, but i nthe end the tried and proven design normally wins out. This is one of those situations.

Not looking to build a better mousetrap, just wondering if one has already been built but they want to sell us new impellers instead.

[RidgeRunner]

Popcorn... Must remember the popcorn...
My flats boat with the jack plate all the way up puts the cav plate (anti-vent plate) nearly even with the surface of the water. At idle I do think there might be a problem with prime on a centrifugal pump.
Not that it matters much, they make positive displacement pumps with harder vanes than the rubber impeller we see in the modern outboard. Jabsco makes a hard vane puppy pump that I like for fuel transfers. Debris MIGHT be the only spoiler and I know it will move a lot more debris than you would ever want in the water jackets of your outboard.
I am not arguing, The question has no correct or incorrect answer!