15' glastron not planing

[nick1224]

I have an early 70's 15' glastron tri hul with a 1969 evinrude 33hp motor. After a bunch of work I finally got to put it in the water yesterday, unfortunately I did not get onto plane. I tried adjusting the tilt of the motor and even took the adjusting pin completely out. It sounds like the motor is reving a bit high but is not cavitating. The current prop is a 12, does anyone have any suggestions as to how large of a prop I could try. The motor has very good torque and hopped up quick but would not level out on plane. Any suggestions would be appreciated.

Thanks,
Nick

 

[180Fisherman]

Re: 15' glastron not planing

Not enough motor would be my guess.

 

[45Auto]

Re: 15' glastron not planing

33HP on a 15' tri-hull sounds like it would be VERY low on power. A friend of mine had a 70's 15' tri-hull with a 50HP motor on it. According to him, it could not plane until they put a "whale tail" on the motor. Even then it was pretty marginal.

Nobody will be able to tell you anything about what prop to try unless you can tell us how many RPM's the motor was turning with your current prop. Was it under-revving or over-revving??? No way we can know unless you measure the RPM. If you "think" that it's revving a bit high, then we'll "think" that it needs a bit bigger prop.

You usually won't be able to get the motor up to full WOT RPM until the boat comes up on plane.

Has it EVER planed with this motor before, or did you just put it on the boat?

 

[nick1224]

Re: 15' glastron not planing

I don't have a tac for it but my best guess by ear is that it was over revving. I put this motor on the boat, the motor the came with was beyond repair. I pretty much gutted the boat, I don't think there is much I can do to make it lighter. Any thoughts on how large of a prop that motor can handle?

 

[steelespike]

Re: 15' glastron not planing

The 33 should plane the boat but be under powered.First be sure it is running on both cylinders.Just carefully pull one plug wire at a time off the plugs.Be sure the throttle plate in the carb is opening all the way.Check the compression.The smallest prop available in 69 was an 11 1/2 so your not far off prop wise.
We had a 40 on a monster of a fiberglass boat back in the 70s it planed easily but was pretty guttless when you started to add weight.