2001 Honda 130 losing power intermittently

<span style="font-family: arial;"></span>After 10 years of absolutely trouble-free service, with nothing but regular routine maintenance, this motor has very recently developed a problem. It will run rough and do no more than 4600 rpm, then smooths out and gets 56-5700 rpm WOT (normal). I pulled the spark plugs and found that #3 is not firing (sometimes); it was wet and the electrodes were darker than the others. There is no apparent pattern with respect to how long it has been running when the malfunction appears. Am I looking at a new electronic control unit($$$)?

I would start with new spark plugs.

Even though it seems to be just one cylinder, drain the fuel in the vapor separator into a glass jar and check for water.

Do a compression test to check all of the cylinders.

There are several things to check before the ECU.

Mike

Thanks Mike, I will try all of the above when I can get back to the boat next week.