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"Hop up" a 25hp?

loosenut

Member
Is it recommended to hop up an engine
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? What all is involved ? Would like a little more out of the engine. It is a '95 merc 25hp, ser# og157655. Any input, good or bad, is appreciated. I'm no mechanic, have rebuilt the carb, replaced the stator& rectifier and a few other parts. Thank You.
 
Since the heads on that motor don't come off, you can't port the exhaust higher without loosing compression. Adding a pipe would help (if you can get away with the racket). I added a larger carb to mine with minimal improvement (if any), so that's a waste of time.

Basically. those are mild ported motors without much hop up potential.

Jeff
 
Yeah. Much more practical to find a moree powerful engine, but not one that weighes a ton! I build what are very light 70 hp Mercs (150 lbs.) for my 9 footer since the stock motor is ridiculously heavy (over 200 lbs.) Even so, I had to go with a long shaft motor since the motor was so low in the water it flooded itself out at idle speed with a passenger aboard. In the below photo, I only made it another 50 feet before the motor died! Note how low the power head is.

Jeff
 

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