Porpoising issue

[Seanymph90]

I bought my son. 16 1/2 sea nymph aluminum boat. It has a 90hp force outboard on it which is a little more than the rating on the boat. It planes out well but if I trim it up any at all it starts to porpoise. Could I minimize it with a different pitch prop?

 

[ahicks]

On a boat that size porpoising is usually about your trim, in my experience anyway.

The only reason to trim up is to get more boat out of the water. With your setup, I'm thinking you already have a lot of the boat out of the water and it's porpoising to tell you something - like you're over trimming!

A different prop to allow you to trim higher might have you thinking about the boat blowing over backwards if you hit a gust or things get sideways on you.

If you want to go fast, consider getting a hull that's designed for that. Your combo sounds like a recipe for disaster if you push it any harder. There's a reason for those HP ratings....

 

[jimmbo]

Try moving some weight further forward in the boat.

 

[WesNewell]

OR engine is mounted too low causing av plate to dig in the waterpulling down back end of boat. When it get the bow up to level the av plate, the bow then drops. Check mount height first.

 

[Faztbullet]

The above.......