cavitation height ??

[Roy Wirebaugh]

Hi folks, I have a quick question on my plate height. I have a 95 alumacraft v16. My motor is a 68 johnson 20hp short shaft. The plate is about an inch below the bottom of the boat. I can raise the motor about 1/2" by placing a piece of wood under the bracket. Will this improve performance or should I not even mess with the 1/2"? Will there be any noticable difference? ..Thanks, Roy

 

[JimS123]

Re: cavitation height ??

My guess is that you will see an increase in speed and a decrease in fuel consumption. Having the cavitation plate at or slightly above the bottom is usually the best place.

Just be sure that when you do a sea trial the motor is firmly clamped to the transom and you have a safety chain attached. When you decide where you want it, drill the tansom and bolt it on.

I have only experimented with larger motors that had bolted on transom brackets. I had one that was optimum at 3/4" up, and one at 1.5 inches up. I keep moving them up till I notice cavitation, then lower it to the previous notch.

 

[tmcalavy]

Re: cavitation height ??

Depends entirely on your boat/hull/keel. Shimming a motor to gain a little height on the transom is common. Try it and report back.