Boat Refuses to trim correctly

[southman61]

I have a 9 foot speed boat (Moccasin is the brand name) with a 25 horsepower Evinrude. I've had some problems with my trim at plane and wondered if any of you have had similiar problems or some suggestions.<br /><br />The problem is this, when on plane at half throttle the boat rides the water perfectly. The water surface area starts at the middle of the hull. At full throttle however the nose dives in, water is sprayed hard to the sides and it bow steers pretty bad. Here are some things I have attempted:<br />-Hydrofoils on the motor help planing and porpoising, I raised the height of the motor so that foils are not in the water when on plane.<br />-I have tried all motor tilt settings, when I trimmed out, the prop comes out of the water, like the boat wants to stay level.<br />-I have tried without the foils, and the results are the same at full throttle.<br />-Removing all weight from the bow has no effect at full throttle, only prevents planing.<br /><br />You might say I have too much motor, but the boat is rated at 25hp and the boat is very stern heavy. It seems like no matter what I do, the boat just wants to be level, which is not the correct trim level. Its a fun boat but I can't get its max speed when its plowing the water. Thanks in advance for your help.

 

[LubeDude]

Re: Boat Refuses to trim correctly

Is this an old boat? There may be a "Hook", in the bottom of the boat towards the back.. Take a straight edge of some kind an lay it along the bottom to see if there is any light shinning through from the straight edge to the boat bottom.

 

[walleyehed]

Re: Boat Refuses to trim correctly

Another thought that comes to mind is that your 25 is pretty light and I think your CG is farther FWD than you want.<br />Some set-back may help the issue.<br />I realise you've removed weight from the front and tried, but you lack the leverage to lift the bow...set-back will give you more leverage.<br />The fact the boat won't even plane with weight removed from front indicates to me being over-powered isn't an issue.

 

[southman61]

Re: Boat Refuses to trim correctly

I'll have to check about the hook in the hull. Another thing about CG, when at rest the bow is higher than the stern, signficiantly because the 25 is heavy for a 9 foot fiberglass boat. The interesting thing is that at half throttle on a plane the boat is riding perfectly but it does not at full throttle, this makes no sense to me. Any more suggestions would be helpful, thanks guys.