'95 Johnson 28SPL - Increase HP

phipps

Petty Officer 1st Class
Joined
Jul 20, 2008
Messages
385
I've seen that the same size (cc) motor can have multiple HP ratings. How do they do this?

Is it possible to increase the HP on my Johnson 28SPL?



Thanks,

Gary
 

bob johnson

Rear Admiral
Joined
Feb 25, 2009
Messages
4,304
Re: '95 Johnson 28SPL - Increase HP

I've seen that the same size (cc) motor can have multiple HP ratings. How do they do this?

Is it possible to increase the HP on my Johnson 28SPL?










Thanks,

Gary

mostly they do it with carb changes and porting...expecially exhaust porting....they will install a cylinder sleeve that has the port holes in different places with different shapes...

by the 90s the days of JUST carb swaps for HP gains were long gone....


and be fore warned just because BRP corp says a carb will fit, doesnt mean it is made to fit...

an example is the 90 and 115 hp motors from the 90s through the mid 2000s

they will list that a 90 hp carb will fit on the 115 hp motor.....and vice versa, but they are two totally different bores on those carbs!!

same for the heads.....but the volume of the 90 is almost .100 deeper than the 115!!! NOT the same heads!!


I SERIOUSLY doubt you would find any one or two items that could substantially increase that motors HP..

if you added 5 hp (about 17%), I bet you would not go 2 mph faster!!!
bob
 
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