1992 mercrury 115 running real high

[countryroad1984]

I've got a 1992 mercury 115. The motor cranks fine, but when i put it in idle speed and it runs at about 1,500 rpms after about 20 or 30 seconds, it jumps to around 6,000 rpms. then after about 20 seconds it drops back down to below 1,500 rpms then works it way back up to 1,500 then shoot to 6,000 rpms and so on.... The boat had been sitting unused for over a year and i was told by one person to first change gas line, it's probably corroded and uneven amounts of gas are getting to the engine. Then someone else told me to clean all three carbs. or should i adjust the idle mixture screw before i do anything. Any suggestions guys? Maybe i am way out in left field and just need some help. Thanks

 

[sb220]

Re: 1992 mercrury 115 running real high

Wonder if your motor has a spark advance/idle stabilizer module on it....Old computer chips that manipulate your timings

I have read elsewhere to get those things off your engine and get the timing set to compensate. If they go bad they can possibly throw your timings way out of whack and pop your engine. Wires tend to frey and corrode.

Sure enough I checked mine and the wires from it were heavily freyed and corroded on the underside and inside the shrink tubing. Took it off and had WOT timing set to stock 23 degrees