57 Evinrude 18 running rough

As the temps were in the 90s, I took a day off and headed to the ocean for a day motoring to the beaches. At first my Evinrude was running great at all speeds but as the day progressed it began running quite rough and sounded as it was intermittently running on one cylinder. It began to do so as I was at WOT trying to fine tune the high speed jet.

I picked up this motor a few months ago and over the time I have rebuilt the carb, installed new float and fuel filter, and new plugs. The previous owner had sometime years past replaced the coils and points as they are the newer style.

I know even new style points and coils go bad, so should I start troubleshooting by just doing a complete replacement with new coils and points?

Re: 57 Evinrude 18 running rough

If it was running Ok before you re-adjusted the high speed needle, chances are good you have dislodged some crud in the carb or got something from the tank. I would re-clean the carb before spending money on the ignition.

Re: 57 Evinrude 18 running rough

oldcatamount said:

If it was running Ok before you re-adjusted the high speed needle, chances are good you have dislodged some crud in the carb or got something from the tank. I would re-clean the carb before spending money on the ignition.

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Agree. If re-cleaning the carb doesn't work, then check spark when the motor is warm. Sometime a coil will cut-out when it heats up. Symtoms would be no power and no high speed.

Re: 57 Evinrude 18 running rough

I was fiddling around with the low and high speed adjustments off and on once the motor warmed up. It wasn't until late in the day when I decided to do one last tweak, that it began to run bad. Coincidence?

Also, if I break apart the carb again, do I need to get another rebuild kit and put in new gaskets?

Re: 57 Evinrude 18 running rough

Should be ok without a new float bowl gasket. Just make sure to blow out all the orifices well, especially the high speed at the bottom. Did you remove the core plug on the top of the carb and clean under there? There are several holes under there that can plug, but usually that affects idling.

Re: 57 Evinrude 18 running rough

By core plug, do you mean the Welch plug? If so, I did remove, clean the area, and install a new one.

Re: 57 Evinrude 18 running rough

1stgenbird said:

By core plug, do you mean the Welch plug? If so, I did remove, clean the area, and install a new one.

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yup

Re: 57 Evinrude 18 running rough

Also, you mention it was intermittently running on one cylinder. I would check your points to make sure they're still gapped correctly. Not uncommon for previous servicing to forget to oil the cam wick which can result in the points closing up. Also check to make sure the upper main seal isn't leaking oil onto the points which can also cause them to miss...