1989 Evinrude 120 intermittant miss and power loss

The motor starts and idles fine, it does not sit for any length of time. First noticed the problem a couple of trips ago when the boat seemed to surge slightly under load. Trip before last the motor started to miss badly and dropped off plane. After a while (idling back to ramp) started running fine again. Thought maybe I'd gotten bad gas, drained and put in fresh and replaced plugs which looked fine. The fuel line and filter are all fairly new and no visable sediment in the filter. Problem still comes and goes and is getting worse, sometimes as surge and others missing very badly and won't stay on plane and then it will start running okay again. Happens warm and cold. My thinking is now electrical but don't know what to try next.

Re: 1989 Evinrude 120 intermittant miss and power loss

Try cleaning all the coils straps and engine block where they are bolted on.

Re: 1989 Evinrude 120 intermittant miss and power loss

Did you check the anti-siphon valve at the fuel tank pick-up? If it is an aluminum one throw it away and get a quality brass one. An in-line vacuum gauge should not read over 2.5"hg on the fuel system. When trouble occurrs does activating the primer pick it back up?? It could be an intermittant ignition problem but I would check the basics first. Electrical parts are not returnable, it needs to be properly diagnosed.