How Much Hull/Water Contact at WOT?

[BlackSmoke]

18' 1969 tri-hull w/OMC 120 hp electric shift Stringer sterndrive. Fixed trim adjustable by bolting front engine mounts in one of three vertical hole positions. Currently trimmed all the way in. At WOT boat runs 28 mph at 4700 rpm w/about half of hull in contact w/water. Should I trim out to reduce hull contact?

 

[Solittle]

Re: How Much Hull/Water Contact at WOT?

The less hull contact the more efficient. What I would do is get her goin about 4500 rpm (so you have some room to WOT) and try it at various settings - - Wait a minute!!! Do you have power trim? You should not have to change the hole in your engine mounts to change trim. <br /><br />I'm at a loss.

 

[93evinrude]

Re: How Much Hull/Water Contact at WOT?

It sounds like you are talking about raising and lowering the height of the motor which isn't trim.If you have no power trim the <br />lower unit can be lifted back and up and you can typically move the position of the pin holding the motor at it's current angle and move it to a new position.It would not involve engine mounts.<br />Can you verify?

 

[DJ]

Re: How Much Hull/Water Contact at WOT?

BlackSmoke,<br /><br />That sounds about right. Your 120 doesn't have a great deal of bow lifting capability.<br /><br />Others, that's the way you trimmed those old OMC stringer mounts!

 

[93evinrude]

Re: How Much Hull/Water Contact at WOT?

Thanks Djohns.Good to know.<br />Sorry for the confusion Blacksmoke.

 

[ScottRock]

Re: How Much Hull/Water Contact at WOT?

Hey Smoke-<br />I just looked at an older OMC somewhere in the 60's. Does yours have the electric windshield on it. I would love to see some pictures of yours if you got any?

 

[BlackSmoke]

Re: How Much Hull/Water Contact at WOT?

Thanks, everyone, for taking a shot at this. djohns19 got it right. I've kept it trimmed in for getting on plane. But, last time out I thought I ought to trim out and see how it affected hull contact at WOT. I'll repost results as soon as weather permits, if anyone's interested.<br /><br />ScottRock, boat is a Thompson Tri-Gull. I'd post a photo if I could figure out how. Guess I have to put one on a web site first?

 

[BlackSmoke]

Re: How Much Hull/Water Contact at WOT?

ScottRock, There's info on my boat at:<br /> http://geocities.com/donstaley/the_thompson

 

[Boatist]

Re: How Much Hull/Water Contact at WOT?

With the manual trim I am not sure you want to trim bow too high as if weather changes and it gets rough you are going to want to get the bow back down. You could convert it to a "Select trim" model but would have to change the front motor mount and get the electric motor and all the screw lift mount. You could trim it as bow high as posible and add hydrolic trim tabs to the boat.

 

[b.gagnon]

Re: How Much Hull/Water Contact at WOT?

I could be wrong but it sounds a bit underpowered, if you don’t know so already don’t ever run that motor and use the trim at the same time. The little fingers that turn the drive shaft wear away in no time at all, and cost more than the boat is probably worth. Those have got to be hands down the worst outdrives ever made.<br />I had one and had nothing but problems with it, and it is so expensive to fix anything on them. I had a 1970 16’evinrude explorer with a 155hp, and the guy I sold it to, did the transom over and mounted an evinrude 175 outboard to it …much better performance. good luck!!!!!<br />

 

[BlackSmoke]

Re: How Much Hull/Water Contact at WOT?

b.gagnon,<br />Yeah, I know not to use tilt to trim the outdrive; that's what the front engine mounts are for. I've had quite a bit of it repaired, but hey, it's 30 years old, it was probably due. It's performed flawlessly since, and I haven't had a bit of water in the oil (yeah, I'm knocking on wood). So far, I think it's OK.