25 Merc Carb Rebuild/reed question

[T Man]

I have been thinking about it, and since I have the gasket kit laying around I have decided to rebuild the carb on my 25hp merc. My questions come from the post re-build tune. I worked for years as an ASE Master Tech, so I understand the nuts and bolts of the rebuild process, but I have 0 experience with 2 cycle engines, I am unsure about how to best get it dialed in after I complete the job. I have used wideband tuners to give me data on the carbs (lean/rich) I have used in the past while building and properly tuning race engines. Since I no longer have access to the wideband, I want to know how you guys are tuning your carbs, post rebuild, so they aren't running lean or rich.

I have also heard about guys upgrading reeds in their motors. I know only the theory behind the reeds (no valves, uses reeds instead, etc), but am unsure how they specifically affect the performance. (For example, I know that long intake runners on a V8 will be better for higher rpm applications, and shorter are for low end torque. I want to have this kind of knowledge for my outboard)

If anyone has any online resources for this kind of information, or would be willing to hold my hand through the process, I would greatly appreciate it.

 

[tigfisher]

hi there, im not that familiar with performance outboard aftermarket parts. but in general on a 2 cycle motor if you want to gain performance, the exhaust porting and a tuned exhaust pipe has alot to do with it like on dirtbikes and jetskis, which you cant do because its molded to the outboard. i would just set the jet screws as it was before you rebuilt it, and check the color of the spark plug. as for the reeds an aftermarket reed valve will have bigger flaps and some have primary and secondary openings to allow more air/fuel mixture to motor. now i do not know if they make performance parts for small outboards

 

[MrSimon]

I agree. Just set the jet screws through some trial and error by listening to the engine .... remember to wait 20 or 30 seconds after adjusting screws to let the engine settle in before making another adjustment.