1980 25 hp johnson seahorse

[stingertrey]

Me and my buddy have been running this motor on a boat for sometime and were wondering what Other motors are compatable with this one for me to swap the carbs to pick up more hp? Thats all I need to do right is swap the carburetor right? are there any 30 or 35 hp carbs that would fit on this and work?

 

[1946Zephyr]

Re: 1980 25 hp johnson seahorse

I have actually seen other posts here where people have used 35hp carburation on their 25's to beef up the horsepower. I happen to own a 1986 model, myself. From 1977 on, they had the 33 cid displacement like the 35's

I would wait to see if someone chimes in here before you take my word as gospel.

 

[rolmops]

Re: 1980 25 hp johnson seahorse

You can indeed do this.However what you increase is the fuel consumption and the RPMs.You will run your 25 horse at 6000 to 7000 rpm,which makes for a short life expectancy.
The other differences are in the gear ratio and the exhaust structure.

 

[G DANE]

Re: 1980 25 hp johnson seahorse

The 20 compared to 25 has a carb with a limiter and a low compression head. ( in 1980 ) The difference up to 35 is mid-section and thru-hub exhaust, intake manifold and carbureator. Later on they all got thru-hub and main difference is then in intake manifold and carb. Changing carb on a 1980 will give you next to nothing.

 

[stingertrey]

Re: 1980 25 hp johnson seahorse

So this isn't possible is what your telling me?

 

[emckelvy]

Re: 1980 25 hp johnson seahorse

If your 25hp has the old-style lower unit which does not have flo-thru exhaust (exhausting thru the prop body) but rather a shear-pin type of drive with plastic nose cone on the end of the propshaft, held in place with a cotter key, it won't accomplish anything by putting a larger carb on it.

The models with flo-thru exhaust had extra breathing capability. Like having larger exhaust pipes on your car.

You could bolt a larger carb on your motor, but all it would do thru the pip-squeak old-style exhaust is make more noise and use more gas.

Later-model 20's & 25's with flo-thru exhaust were 'strangled' at the carb end by either a very small carb/manifold hole, or just a smaller-throated carb. These you can modify successfully and have a stronger-running motor.

If you do happen to have one like that it might work, however from the description/year it doesn't sound like it.

HTH..........ed

 

[14ftgrumman]

Re: 1980 25 hp johnson seahorse

Easiest way to get more power out of a 25HP is to buy a 35 or 40.

Easier and less expensive in the long run, not to mention a lot more dependable.

 

[jasper60103]

Re: 1980 25 hp johnson seahorse

Easiest way to get more power out of a 25HP is to buy a 35 or 40.

Easier and less expensive in the long run, not to mention a lot more dependable.

I agree. I have the same motor. It's a good runner and simple to work on.
I may eventually upgrade to a 35, but plan to keep the 25 as a backup.