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'99 25HP conversion to 30HP??

matt61076

New member
1999 Tracker Marine 25HP 2-stroke.

I've read that some 2-stroke 25HP's can be easily converted to 30HP. Does anyone know if mine can be converted? If so, any links to instructions would be much appreciated!!

thanks!
 
Not sure where you heard that.

The 25 shared a powerhead with the 20 horse (about 25 cubic inches of displacement), not the 30 (39.4 cubic inches of displacement which was shared with the twin cylinder 40 horse). So you can "detune" yours a bit but can't bump it up enough that you will notice.

In small outboards the max horses is pretty well limited to the displacement (on a 1:1 basis), and the 25 is already at the max.

On models that can be converted 9.9 to 15, 20 to 25, 30 to 40 etc, the cost is usually significant. It can encompass changing the carb or reed valves/plates, altering or changing the exhaust plate/tube etc (big bucks compared to the price of the motor).

AND, if you live in the U.S. it is illegal to alter the horsepower of the motor (unless you have a racing exemption - thank the EPA for that law). Ok, that wouldn't stop alot of guys, but should an accident ever occur and things were investigated you can be sure that the fact the motor was illegally altered would weigh heavy on determining fault (so something to consider for US residents).
 
..."...if you live in the U.S. it is illegal to alter the horsepower of the motor "

If that's the case, I believe that's only on newer motors.

Jeff
 
Here's the good word from Merc -

EPA regulations prohibit changes to engines that could affect emissions limits. Per the service manual, "The dealer and/or consumer is not to modify the engine in any manner that would alter the horsepower or allow emission levels to exceed their predetermined factory specifications." The only changes permitted are carburetor jet and gearcase/gear ratio changes for high altitude operation as detailed in applicable Mercury Marine Service Manuals.

The EPA regs that they reference came into effect in August of 1996 - so yes Jeff, like you I have old motors (newest is a 1991) and it doesn't apply to us (or me in particular living north of the border), but in this case, if this 99 model resides in the US it legally can't be modified (and will have an EPA sticker on it somewhere to show compliance).
 
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