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In article ,
says...
Hi folks,
I have an Evinrude 70hp triple on my everyday openbow runabout.
I would like to try to make 100hp, but without revving it to death,
just more ponies in the normal 4700 to 5200 range.
The engine seems very durable and has the large gearcase used on
motors up to 140hp, so it would seem like a good candidate for a
bit of a build-up.
More performance from the same displacement and red line means that you
have to move more fuel/air through the motor, or switch fuels.
Bigger carbs and a tuned exhaust is the obvious first step. Port work
will add some CFM as well.
Turbo-charging would be another way to go, but unless you have deep
pockets and enjoy such challenges, I'd stay away from that engineering
exercise.
And of course, there's always "the bottle" (nitrous).
Switching fuels (methanol) means new or altered carbs. Given your
expressed desire to not push the red line, I don't believe you'd gain
enough by switching to alcohol to make it worth the effort.
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