Increasing hp on 1974 Johnson 25 hp

[Muzza]

I have a 1974 Johnson 25 Seahorse.I recently spoke to an outboard mechanic
who said he could convert this motor into a 35 hp just by changing the carb.
Can this be done? I've read so many conflicting posts on this subject that it is hard to know what's what. I really do not want to damage my existing motor.Is it too good to be true or is it worth trying.
Any ideas?
Thanks
Muzza

 

[R.Johnson]

Re: Increasing hp on 1974 Johnson 25 hp

Your engine is 22 cu.in. In 1977 the 25, and 35 shared the same block, but it is 31.8 cu.in. Your not going to pick up 10 HP with a carb change.

 

[wbeaton]

Re: Increasing hp on 1974 Johnson 25 hp

If an outboard mechanic said that to me I'd be suspect of his credentials.

 

[rjezuit]

Re: Increasing hp on 1974 Johnson 25 hp

That 22 cubic inch engine is stretching to get to 25HP. It is the same powerhead that started out as the 18HP in the late 50's ('57) So the carb and exhaust changes were already made at the factory to squeeze out the extra 7 ponies. Rick

 

[F_R]

Re: Increasing hp on 1974 Johnson 25 hp

What rjezuet said is true. What he didn't say is that it took more than just a carb to get the power. The pistons and cylinder head are different too. No free lunches in the horsepower barn.