Hello I have a 2000 yamaha c115,non injected,engine mounted on a older 17 aquasport center console,21 pitch prop.It will turn 5300 - 5500 rpm. depending on weight.The engine runs great while planed off.Even when you first leave the ramp idling 15 minutes,with clean plugs,no problem.The first time you plane off, perfect,the problem starts when you decelerate back to trolling speed or idle.It sounds like its running off 2 cylinders or so.After that, it will not ever idle right again.Come home and clean the plugs,idles and runs good.The carbs were just done and fuel pump replaced.So when the plugs are clean it runs,ignition must be ok or not? First time, I took off one wire at a time,and the port top and bottom cylinder were the ones foul.All look rather wet.Would it mean both carbs would have to be bad in order for all plugs to be wet.Idle screws are set at 1 turn out.Engine is new to me,I don't suppose a decarb would fix this,probably wouldn't hurt though or am i wrong?Thanks 233
while a decarb wont hurt I doubt it will help. you need to carefully check the ign system and your oil mix.plug fouling is a symptom that all is not well in the motor. when you say they are fouled what do the actually look like? start with the basics, spark test at about a 7/16th gap and compression test. carbs just done is meaningless to me cause I redo them on a weekly basis . but for now you need to insure the ign system is capeable of making spark with reserve voltage and the compression is correct.
Thank you,The spark plugs are really just wet,not black.I checked the fuel for water,its ok.If the plugs will jump the 7/16 gap,does this mean there is reserve voltage.A friend,who is a yamaha tech, did the carbs.I know that doesn't mean he didn't miss something.I did check compression and it was 125 on each cylinder.I will look into the spark,if good I guess its back into the carbs.I'll return later with results.Thanks for the help, 233
its still possible a float or two is not set correctly, new fuel pumps have been known to be bad, but if the ign system is not capeable of keeping the mix lit wet fouling can result as well.
yamaha 115 fouling plugs
you need to carefully check the ign system and your oil mix.
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