Re: 1974 Evinrude 9.9 won’t idle at low RPMs, need help

[optsyeagle]

All the carb kits I have bought (BRP brand) have a slow speed bearing and a retainer for the slow speed jet. They also have a welch plug in them.

Definitely a good known carb will help you isolate where the problem actually lies.

I don’t want to send you in a million directions but if you are writing down these things, put the carb at the top of that list. Using a known good one would answer the question on it, once and for all.

The next thing I would be thinking about would be the point gaps. If you look closely that the throttle cam you will see that most of the slow idling happens when the carb roller is not even touching the throttle cam. This means that the carb throttle is completely closed. The question arises then, how is the motor still throttling down when the throttle butterfly is closed. It happens because the spark timing is being retarded (changed) as you move the throttle grip. As the spark timing happens later then top dead center the RPMs slow down.

So, with all that said, think about what would happen if instead of having the specified 0.020"gap on your points, your gap has decreased (which they do over time and use) to something like 0.005" or something like that. A point gap at 0.020" ensures your spark is properly timed at top dead center. If your point gap is reduced, the spark happens later, just like what happens with your timing advance when you reduce throttle. At higher RPMs this won’t matter too much (won’t stall but will give reduced top end performance) but at lower RPMs you might find that a spark that is timed to late, with an amount of gas that expects a better timing point, might just cause the motor to stall.

Anyway, I’ll cut to the chase. If the carburetor ends up being fine, I would check the point gaps. With this motor you really need to adjust them about every 3 years anyway, since they will narrow over time as the rub bar wears down.