increasing HP from 20 to 25

[tugboat80]

Subject 20 hp Evinrude mid 80's same bore and stroke of 25 hp model. What is possibility of bumping max hp to 25? What parts necessary. Is this just due to increased max RPM?

 

[jbjennings]

Re: increasing HP from 20 to 25

You'll need a 25hp carb, possibly a 25hp exhaust tuner, possibly a 25hp cylinder head. The increased hp is due to increased max RPM.
YOu'll need to get on one of the parts sites like crowleymarine.com or marineengine.com and compare parts diagrams to see where the differences are. You may actually be able to get the increase from 20 to 25 with as little as taking the carb off, dremeling out the intake manifold to equal the size of the carb throat, and bolting everthing back on. I'm not sue without checking parts diagrams.Good luck,JBJ

 

[boobie]

Re: increasing HP from 20 to 25

Not worth the effort for 5 hp. If it was 25, yes.