1975 Evinrude 115 missing at idle - The Hull Truth

DJD775 · 05-24-2007, 10:13 PM

I'm working on a 1975 evinrude 115 that hasn't been started in a few years. I replaced the water pump and spark plugs first. It runs but at idle it misses every once in a while. I pulled the plugs and noticed that on one bank of cylinders the plugs looked clean with the electrode metal visable and the plugs on the other cylinder bank were dark with no metal visable. Anys suggestions?

A1 Outboard · 05-26-2007, 09:05 AM

It's likely that the on bank of cylinders is not warming up enough for complete combustion and are close to fouling. You would have to use an infrared temp gun to make certain of the temperatures. It could also be weak ignition system. The coils were prone to cracking and should be replaced if cracked.

Since the motor was stored for a long time, it would be a good idea to clean and rebuild the carbs per the service manual using the factory repair kits. There may be stale fuel deposits inside them affecting the idle mixture and today's alcohol and chemically induced gasolines will soften and may destroy the orginal carb gaskets on that 32 year old motor.

DJD775 · 05-26-2007, 11:28 AM

Thanks A1. There definatly are a few cracked coils on the engine. I wasn't sure until now if the cracking was just cosmetic or had an impact on the spark. I can borrow a friends infrared thermometer and check the temps also. If one bank ends up being cooler than the other what would cause that?