Hot rodding an OMC 70hp triple, any leads?
 

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.

I know I could just put a 100hp 4 cylinder on my hull, but that kind
of takes the fun out of it. I have 2 of these 70hp triples out in the
garage missing various external parts, and either of these could be
built up, while still running my everyday engine. It would mean more
to me to hear somebody say "Damn, that little 70 of yours really kicks
ass", as opposed to "So, you got a V4 back there".

It seems Montyracing doesn't mess with triples, only V4/V6 stuff.
Anyone have any thoughts on my project? Any leads? Oh, BTW, I trailer
the boat with my 1948 International KB1 pickup with a 142 cubic inch
blower sitting on a Chevy 350, and no, I don't mash it with the boat
back there, as I think snapping the hitch ball completely off is a real
possibility!

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.

Well supercharge the outboard too ... 8 psi should give the required
additional 35 hp :-)


I would like to try to make 100hp, but without revving it to death,
just more ponies in the normal 4700 to 5200 range.