Prop or trim?

[Retired Wrench]

I ran the boat for the first time this season with the 65 hp Johnson we put on it. The old 75hp we took off off had a 10 in. prop and this 65 has a 12 in. Accelerating away from the no wake zone it "digs in" and the bow is up really high. We moved the trim pin in 1 hole toward the boat and it seemed to help. I was thinking of putting the smaller prop off the 75hp on to give it a little less bite.

 

[IRBFishin]

Re: Prop or trim?

What is it hooked to? I had a 70hp Johnny on a 16' bass boat (glass) with a 13 1/4 x 17 prop. After lots of carb work it would do "okay" but I came to realize that the tri-hull design, waterlogged weight and motor/height combination would never make me happy. Got rid of it but not before I changed to a 13 pitch prop. Seemed better out of the hole but top end suffered. Trim should be all the way down to get to plane, then trim up slow and you'll feel it flatten and speed up til you find the sweet spot. If you're bow is up high you may not be trimmed down flat, forcing your butt down and your nose up.

 

[Maclin]

Re: Prop or trim?

If I am reading this correctly, you put on a smaller engine with a larger pitch prop? Generally when you go down in power you also need to pitch down some, or at least stay the same. I think you already know what to try next by way of your last sentence.

 

[Retired Wrench]

Re: Prop or trim?

This is on a 1960 Lone star fiberglass

 

[steelespike]

Re: Prop or trim?

What year are the motors?If the boat is 14ft its about 370 lbs.
That hull looks like once up on the water it could go pretty good.
Your probably over propped,with the year of the motors we can figure the gear ratio.
I think the the 75 is an odd 1.15 ratio the 65 could be 2.41.depending on the year and number of cylinders. Thus the larger pitch on the 65 may be close

 

[Retired Wrench]

Re: Prop or trim?

the 75 hp was a 1964 and the 65 hp is a 1968. Both are V4's.