bigger carbon 18hp 1959 evinrude help

[ronboonville]

I’m working on this motor and want to get more power and or more rpm’s. can I put a carb from a 28 hp omc on it to do that?

[chris-p]

Nope. Sorry but if you need more power, upgrade. Easiest.

[ronboonville]

Thanks, I just realized the carb I have is off a Gale and the linkage is on the wrong side!

[fleetwin]

Yeah, the good ol 18hp OMCs surely are not gonna win any races. But, there are different pitch props available, you may be able to trim the engine out a bit, or perhaps raise it up on the transom slightly. I wouldn’t mess around with different carbs. Needless to say, make sure the mag plate moves freely and the carb butterfly is opening fully.
Keep in mind that you will need an accurate tachometer if you want to mess around with different propellers, a GPS is handy as well.

[ronboonville]

I tried trimming it out and that didn’t help. I will check the butterfly and mag plate next. Sounds like that could be the problem. Also I may be able to shim it up maybe an inch or two. Thanks for the ideas! I have had plug wires cause the plate not move all the way.

[chinewalker]

About the only wAy you can get more power out of that motor would be to swap a late 1960s 25 hp powerhead onto it, carb and all. It’s the same displacement as your 18, but has different pistons, crankshaft, head, porting, etc. No, it is not easily possible to convert your 18 to 25 specs.

[phil-b]

The 25 hp midsection has exhaust tuning, and the gearcase has improvements too!

[ronboonville]

Thanks again for the info. Owner told me today the butterfly was not opening all the way. I’ll check that and the mag plate.

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