Porpoising like a BAD BOY! Any suggestions??

[Woodboater]

I have a 1948 11' outboard mahagony runabout with an OMC 30HP. If and when I get it up on plane, usually just myself in the boat, it bounces like a badboy. The transom is straight, but a motor board is attached and it sits at about 12 degrees from straight up. I have fuel tank, and battery at the transom and 2 ft forward is the bench seat. the rest forward is empty. Do I need to move weight forward or re-angle the motor where the foot is "under" the boat more? the hull weight is about 165lbs without motor and gear.
H E L P ! ! !

[inboats]

Sounds to me like that is your problem. Your motor should have a trim pin to let you adjust the angle of your motor in relation to the transom, which in turn will raise or lower the attitude of your boat.
Closer to the transom lowers the bow,further away lifts it. However if it is trimmed up too high it can be very difficult to come on plane as well as porpoising once up there.
I would trim in until you hole shot increases but not too far that your top end will suffer.
Good luck.

[crazy horse]

My last wood hull started porpoising and it turned out to be the bottom of the hull. It had a small amount of bow in it. It was a old 11ft. class D runabout with a 50 hp four cly. merc.

[baddjonny]

Or a few shims under the the rite ribs.

that was the wood way when I was a kid.

baddjonny

[airide18]

Sounds like you need some transom shims.

[Pro-Comp 2.5 260]

What type of prop are you running! 4 Blades help with this. And moving weight to the front should help.

[Woodboater]

I've posted this question on another board and have tried , tested, and found the solution. I fabricated a battery box and mounted it to the stem (front bow support beam) and it flattened it right out. Doing 37-38 mph (GPS) with an old Johnson Big Twin 30HP ! Very happy now.
Thanks everyone for your input with my problem.
Travis