1970 Evinrude 9.9 issue

[Coach]

I have an old 9.9 that is having a wierd issue, at least to me, hopefully someone can help me out. The motor starts just fine but when it warms up, it starts sputtering like its missing a spark plug. After it cools down it will be fine again for a little while, then it will start sputtering again.

I do not want to stick much money into it but I do not want to get rid of it either. If anyone can help me out, i would really appreciate it.

Thanks in advance for any/all advice.

[marine_man]

Sounds like a ignition (magneto / electrical connection?) Is getting warm, expanding and losing contact with the mating component.

I'd take a look at your ignition connections and make sure everything is tight and not cracked.

marine_man

[Scupper]

Fuel oil mixture...

My brother in law was having similar symptoms years ago with a 15 hp that I had owned for years with no problems. We went over everything and could find no problems. I asked him what oil/fuel mixture he was using and he said he adds oil as needed. Fresh fuel and proper amount of oil and it run out with no problem.

If you haven't put in fresh fuel and oil for a while and the prescribed mixture, I'd start there. If that doesn't improve things I would move on to what Marine_Man prescribes.

Good Luck

[boatfixer]

Do a compression test and let us know the results. We can go from there