Cavitation Plate Height Question

[Klink]

I've read here that ideally, the cavitation plate should be anywhere from one inch above the bottom of the stern to 1.5" below it. Now, I have a 1992 6hp Johnson and it has 1/2 the water intake above the cavitation plate, the other half below it. The other day when testing it in the tank, it would not draw water at idle unless the top half of the intake was under water. Does this change at high speed? In other words can the cavitation plate run out of the water at high speed and the engine still draw water?

 

[midcarolina]

I would ensure the top of the water intake stays below the water line..........if you get too aggresive with the motor height you will suck air instead of water at high speed.........if the pump sucks any air the pump will not pump properly.
Depending on the boat the motor was on I always set mine up so the top of the intake was level or slightly below the bottom of the boat.........just depends on the type of hull.

 

[Klink]

Excellent, thanks for the advice.

 

[F_R]

It would be hard to imagine any situation where the intake would be above the waterline at idle when mounted on the boat. Also, there is very little reason to jack up a 6hp so high that it would have a water problem. After all, this ain't no race motor. Put that poor thing down in the water where it belongs.