1985 Yamaha three cylinder 70 horsepower

I keep reading about rough idiling at low rpm. I have the same problem. Mine never fails to run but the idle is rough at low rpm. Runs great other than that. It will also be hard to start sometimes. Have tried to adjust carbs and it may have helped a little but problem still exists. As for hard starting, once it does start it is fine for the rest of the day. A friend said sometimes if you just let it sit for a few minutes after initial attempt it may then start as sometimes the motor will create some kind of vacume that will go away after sitting for a few minutes. Once I loosened the gas tank cap a little and it started right up. Another time I got frusterated and pulled the cover off the carbs to see if it was getting gas, tried it again and it started right up. I don't know if any of this actually had an impact or if it was just ready to start regardless. Ideas?

When a modern motor " won't start " it is often a problem of a poor starting procedure , slow cranking starter motor or a problem with the motor.--------------------So post the results of a compression test.------- Will spark jump a gap of 7/16" on all cylinders ???.------------Your motor " does not create some kind of vacuum " that goes away, that is just another " tall tale " one of many about outboard motors.