cavatation plate position

[Dorkynhymer]

I have a 1969 fiberglass tri-hull bass boat 16 ft with a 1969 Johnson 33hp my boat will not fully plane but gets close! I have found that the cavitation plate is 3 1/2 inches below the bottom of the boat. is this keeping me from planning?.i would guess top speed now is maybe 20 mph but the bow rides high. wondering if a hydrofoil would be the answer...any advice would help..sorry I have no photos yet

 

[Triangleboater]

Re: cavatation plate position

Really the plate should be even with the bottom of the hull....I would raise the engine up somehow, just rig something up...plans are all over the place and if you post phots, we can help come up with something...

I would first raise the engine to the proper place, try that out and go from there. If that doesn't work, try trimming the engine and shifting weight around to the bow. that should bring it down and get it to plane out better.

 

[jsr_1648]

Re: cavatation plate position

I'd say the motor is too low. when i got my boat my motor was too high and would not even get close to planing out. Now my anti cavitation plate is even with the bottom of my boat and when im on plane its perfectly visible and it works great.

 

[JB]

Re: cavatation plate position

Sounds like a lot of un-needed drag, Dorky. The anti-ventilation plate (often incorrectly called a cavitation plate) should be right at the surface when on plane. You can probably get her to plane by raising the outboard so the AV plate is even with, or slightly above, the bottom of the transom.

 

[airshot]

Re: cavatation plate position

Along with getting the cavatation plate even with the boat bottom, how does the motor run? Weak performance will not get you going, a 33hp on a heavy tri-hull is working hard. Also the prop....is it in good condition and the correct pitch? Check to see if you have any excess water stored up in the hull or soaked foam flotation as this will create excess weight. Good luck

Airshot

 

[Dorkynhymer]

Re: cavatation plate position

I have photos now - how do I get them posted? its a smaller Fiberglass trihull 16ft- I just replaced the floor -all wood was rotted and the foam waterlogged- guessing I took out 300lbs wet material! the old 33 Johnson has 118-120 compression and I put on a new prop -10 1/2-12 and also put in new plugs , points and condensers..the motor runs great. I'm making a home made plate (1/4 steel) -U shaped to slide onto the transom to raise the height by 3" . I will drill and bolt it to the transom and mount the motor to it and get the anti-cavatition plate even with the keel. i'd like to use aluminum but cant find it. can anyone tell me how to post photos of my boat from my Facebook to IBoat?