1970 Johnson 25 hp - upgrade power?

[cparkerc]

Evening,

Tried the search but did not find what I was looking for, so here goes...

I have a 1970 25 hp Johnson that runs really well, but I would like a little more power. I don't want to add any weight to the stern of my boat if not neccessary. I know some outboards can be converted to put out more horses, is mine a candidate? If so, can someone please explain what's involved or provide a link? I'd appreciate any help!

Thanks

cparkerc

 

[ultra353]

Re: 1970 Johnson 25 hp - upgrade power?

Not on that motor, its already tweaked for max power. The motor in question that can be upgraded (Debatable on how much of an increase by the carb and manifold swap) is the later model 20-25 hp from `76 -on i believe . Not positive on exact years though. There is a large thread on the subject in this forum.

 

[Chinewalker]

Re: 1970 Johnson 25 hp - upgrade power?

Your motor is a 22-cube block, derived from the earlier 18hp models and is pretty well maxed out. The later 31.8 cube 25 horse models are of the same family as the 35s and some can be upgraded with some parts swapping...

 

[cparkerc]

Re: 1970 Johnson 25 hp - upgrade power?

Dang it!

Thanks for the responses, I do appreciate it. Guess I'll start thinking about swapping motors, or just be satisfied with the good running motor I've got.

Thanks again,

cparkerc

 

[dkonrai]

Re: 1970 Johnson 25 hp - upgrade power?

what are you running the motor on? i have almost the same motor and my 14 foot tin boat flys. motor is a beast. are you not getting the rpm's? or slow to plane?
dino
heres a vid i shot. had to back off the throttle.