25hp 2 stroke cavitating

[lcs215793]

Hi folks I have a 2009 25hp 2 stroke on a 1436 tracker topper boat 05 model and it is cavitating bad. When I first put it on the boat it wouldn't even get on plane. I drilled holes in the prop 1/2" in diameter and it would finally plane but still cavitating bad. I ordered a stilleto prop with 14" of pitch for it and got the same results will plane but still cavitating. Any suggestions?

[99yam40]

Are you sure it is cavitation and not ventilation?
Is your motor set up properly?
anti- ventilation plate at or just above bottom of boat?
Maybe this will help understand what the difference is
http://www.boatfix.com/how/props.html

[lcs215793]

This anti-ventilation plate does it mount to the boat or on the motor?

[99yam40]

It is part of motor

[lcs215793]

Ok so I seen pictures of the anti-ventilation plate and built one out of thin aluminum. It measures 10" wide to ensure I got the prop covered. Mounted it on my motor and tried the boat. Still having the same problem. I also moved my motor back away from the transom on a frame I built trying to get the motor back to some cleaner water hoping that might help. Still no change. If I have done all this to the motor and have had no change at all I'm wondering if the maybe the boat is the issue? Would any other flat john boat have different characteristics of water leaving the back of the boat? Before this 25hp yamaha I had a 15hp yamaha that run like a scalded dog on this boat. The transom on my boat is 16" and I had the 15hp mounted 1" above the transom and never had any trouble unless I was in a hard turn then it would ventilate a little, but still nothing like this.

[99yam40]

lower the motor to see if that helps, never heard of some one needing to drill holes in a 25 HP prop

What are your RPMs doing?

Could it be the motor is not running properly?

[lcs215793]

I've been up and down with the motor. To go any lower I would have to cut the stock transom. I'm at a complete loss here. Don't know what to try next. The motor seems to be running fine. Don't know about the RPM's don't have a tach. If you work with it will get up on plane and you can let off the throttle it wil stop slipping (it feel like a transmission shifting gears) then you can go on easing the throttle to it until WOT. Speed at WOT is about 38mph.