Having problems with my 85 merc, motor will idle only with fast idle engaged (barely idles normally after running for a good 20 minutes). On the water the boat pulls back quickly then releases like its missing and this occurs throughout entire RPM cycle up to WOT, problem does not get any better after letting it run for awhile. I am down to jamming the fast idle down and at the same time throwing it into gear just to get her going. The guy I bought the boat from says its most likely the stator and told me how to check with an OHM meter, he said he believes the trigger was recently replaced and has pretty much ruled out a fuel starvation problem. Now, if you couldnt already tell I know very little about outboards and inclined just to take this into a shop but down here in Biloxi marine mechanics are hard to find after the storm, and I have read horror stories about outboard repair bills. My question is: is there a quick and simple way for me to really diagnose and isolate this (yeah right!), and does anyone know a good reputable Merc mechanic on the gulf coast of MS or even over in Mobile?<br />makoshark - Biloxi, MS
<br /><br />First thing I'd do is pull the sparkplugs and see how they're burning. They should all look about the same. One or a few that look way different than the others usually indicates a problem, and which cylinder(s) the problem is with. Depending on which are different, we can narrow-down the possibilities for you.<br /><br />Just one different sparkplug burn would eliminate the carb as a possibility. Each carb feeds two cylinders, so two neighboring sparkplugs would be affected. If you have two odd ones but they're not neighbors, it could be a switchbox problem. There are two and they fire in pairs. But the pairs they fire aren't usually cylinder neighbors. There are other possibilities, but that's a start.<br /><br />A good way to check for spark while running is to connect an inductive pick-up timing light and tape the trigger on. Place the light somewhere you can see the flash and have a run. If it misfires, you'll see it. If it comes and goes, you'll see it. But only if the problem is spark-related. Check each of 6 cylinders in successive runs. If the flash is good on all and the motor is still misbehaving, then I'd start looking at the carb(s). If they all start misfiring over 3/4 throttle or so, then I'd be looking at that stator.