65 MFG Niagara Outboard trimming

[dcarmack]

I have a 1965 MFG Niagara 15ft boat with a 75 HP Johnson electramatic outboard powering it. I just got it on the lake for the first time last weekend. Outboard runs fantastic, but my issue is that I have to be at practically full throttle for the boat to plane out. When it does it springs out of the hole like a rabbit and runs like a bat out of hell. Its like an amusement ride. It scares the wife. When I back down on the throttle once planed out it slows down some and eventually falls back in the hole. I have no experience with these things so where is the best place to get information or help in setting this boat/motor up for tuning this issue out?

 

[steelespike]

Re: 65 MFG Niagara Outboard trimming

If the bow bounds up and down by itself(no waves) you may be trimmed out(up) too far if you trim in it will stop and also plane easier.
OK do you have any particulars on actual speed and rpm.If power trim; trim in(down) for hole shot
gradually increase trim (up(out) for best speed for runnig at reduced speed trim in as you slow
Slow gradually until just befor dropping off plane.If no power trim; trim in to lowest setting and keep increasing trim (up) till best all around is found.If you have tanks and batteries in the stern you may need to move some forward.
If the flotation foam under the floor has absorbed water you may never solve the planing issue till you replace it.

 

[dcarmack]

Re: 65 MFG Niagara Outboard trimming

This is an older boat with no power trim. The outboard may be too heavy for the boat, actually. I have heard that the spec for my boat is 40hp, but this one came with a 75hp. It didnt seem to make any difference in performance with a full or empty 6 gallon gas tank, but I can see what you are saying about shifting the load around.

 

[steelespike]

Re: 65 MFG Niagara Outboard trimming

The 65 Niagara was rated for 50 hp. boat has a center line length of 14'4" gunwale length is 15'6 1/2". weighs 520 lbs. Boat is really a 14 footer.
A 50 weighed about 200 and the 75 about 240.
Todays 40 hp weighs about 240.
So your way over powered, weight isn't too bad.There are any number of legal issues when that far over the rating.I'd start searching for a 50.