exceeding the top speed?

[dukchunter]

Hey guys I have a 1994 Johnson 10 hp on the back of a 12 foot homemade sneak box. The motor is converted to 15 hp. I've been having issues with this motor running correctly for over a year since I had a buddy borrow it and blow the lower unit. Long story short I got it running good and took it out for a test run. Motor ran great but at wot I could not keep the front of the boat on the water. Drop it down to 3/4 throttle and it planed level as it always did but open her up and it would just bounce and get down rite hairy to control. The only change I made to the motor was go with a higher pitch prop. Running 13 pitch as the old prop allowed the motor to over rev. Am I just exceeding what the boat can handle? We are talking 35 mph gps

 

[MikDee]

Wow! 35mph is really moving for a 12ft boat! If you want to stabilize it, just get yourself a Doel fin! This should calm it down, and keep the bow down. Make sure it's a Doel fin or exact copy, anything else might be too big!

 

[kbait]

pull the tilt pin all the way in. If that doesn't help, distribute all weight to front of boat..

 

[dukchunter]

I'm strongly against a hydro foil although it may fix the issue. I run a shallow rocky river and hydrofoil don't like rocks. Kbait, I had the trim pin pulled so the motor could be in the furthest down position. Also all the weight as well as me being in front of the boat. This included a full 6 gal fuel tank, battery and myself. As I thought that would fix the issue it made it a little less hairy I am still not comfortable with what it was doing. The boat is 1/4 ply with fiberglass and could feel the integrity of the boat being comprimised.

 

[GA_Boater]

Doctor, It hurts when I do this. Says the doctor, then don't do that. You don't have to run it wide open.

You have a 13 pitch prop, what was on it before the change? Can you post a couple of pics of the boat?

 

[dukchunter]

I have a couple here. And I was mistaken it is a 11 pitch up from a 9 pitch. I had a 13 pitch and I didn't like it. Sorry for the mix up. Any way. Attached is a pic

 

[dukchunter]

Or the pics won't attach....