Should I raise my engine or not?

[Hukeedo]

I have a 1978 15 ft Tri-hull with a 1960 Johnson 40 HP SS that I put on it. I am not getting the speed I feel this setup should produce at WOT. I was told to raise the engine up but to be careful due to the age of the engine the water intakes are set higher on these engines. I think my engine sits too low for the boat ( attached are pics). It seems if i raise the engine, the engine will be sitting almost at the top of the transom and would put too much strain on the transom.It's only running at about 15 or 20 mph right now. Can anyone tell me by looking at the pics what I should do? Or would a newer year engine be the way to go? This engine does run really good.
Thank you sincerely for your reply's.

View attachment 34143

View attachment 34144

 

[Dhadley]

Re: Should I raise my engine or not?

That's fairly low but here's something to keep in mind - the props for that style gearcase don't have near the technology that a thru hub prop of today has. Some of those motors had holes in the stern bracket so you could bolt them to the transom if you went high enough that the clamps wouldn't work. But you're back to the prop issue and the water pick up issue.

 

[Bifflefan]

Re: Should I raise my engine or not?

Id leave it, and just enjoy the ride.
Then look for a little more motor. I have a 16' V hull with an 85HP. it goes plenty good with 4 people and a 4 person tube on the back.
40 is a little small and as stated the prop is not to up to date eather. Probably doing all it can.

 

[Hukeedo]

Re: Should I raise my engine or not?

Well, thats kinda what i was thinking, just enjoy it for what it is and then maybe upgrade to bigger motor next year Bifflefan.
Dhadley, thats a great point about the props, never thought of that, but hey I paid 300 bucks for a whole boat, running motor and controls and trailer with titles and put the motor on the tri-hull. So I guess I got a deal and should just be happy to just be on the water and moving. Thanks guys, really appreciate the info and help, glad I posted before i spent alot of time and work for the same result, or worse!

 

[Chris1956]

Re: Should I raise my engine or not?

That motor is an appropriate HP for that style boat. It is set a bit low. The grating above the antiventilation plate is the water intake for reverse only. the forward water intake is behind the prop. You will want the A-V plate even with the bottom of the hull, or slightly below it.

I would baseline the performance using a GPS, and then raise the motor 3/4" using a piece of 1 by lumber on top of the transom, under the motor, and recheck it. It may make a difference. it will not harm a good transom, BTW. You may be able to go 1-1/2" up in height, but make sure the thumbscrews have a solid hold on the transom or the motor may go swimming. There may be places to bolt the transom clamp to the transom. You should consider this.