'71 Johnson 125 hp low rpm problems

[Old Head]

I'm hoping for some help with an idle problem. This motor runs great over 1800 rpm. Below that, it's tough to keep running. It runs right for a couple seconds, then seems to stop firing on several cylinders. Sometimes it catches again and will idle right for another few seconds, sometimes it just dies. I've rebuilt the carbs twice with OMC kits, including cleaning the idle jets under the plugs. It has good spark, good compression, a year-old fuel pump. Very frustrating.

 

[ledgefinder]

Re: '71 Johnson 125 hp low rpm problems

Might be the sensor in the timer base (not carbs).

 

[Old Head]

Re: '71 Johnson 125 hp low rpm problems

Wow. There's an idea. How do you check it?

 

[Old Head]

Re: '71 Johnson 125 hp low rpm problems

Ledgefinder you rock. I couldn't get it timed, using Joe Reeves' method, so I pulled the flywheel. Lo and behold, the woodruff key was broken and the flywheel was off kilter. Reinstalled everything and retimed. Then fired it up on the muffs. Idles pretty smooth -- nothing like before -- and it stays running at 500 rpm. I won't be ready to declare a fix until I put it on the river next weekend, but things look promising.<br />Thanks a lot.