[sarnajo]

I have a 1989 150 Yamaha that stalls while idling. The problem seemed to occur after I put in new plugs. I went back to the old plugs and the problem was better but did not fix it. In addition to the plugs, I replaced the water separator and fuel line. Does anyone have any other ideas on how to fix the problem or narrow down the cause?

[jim dozier]

When you replaced the plugs did you replace them with the correct ones. Your engine may or may not have had the correct ones in there to begin with. Check your manual. Did you gap them according to the manual specs? Changing the gap changes the ignition timing as well as the quality of the spark and may have slowed your idle speed to below the minimum. It is also possible to get a bad plug right out of the box.I would suggest you check the gap and heat range of your plugs. Then you may if necessary just need to increase your idle speed by the method described in your manual. Some engines use timing, some use carbs, and some use the throttle cables. If that doesn't work you may need to adjust the mixture on the carbs. If that doesn't work it may be time for a carb rebuild.

[sarnajo]

Thanks for the info. The other day I had checked all the plug gaps and increased idle speed and it still stalled.Today I again put in the new plugs and saw the problem got worse. I then went back to the old plugs and the engine didn't stall at all (very strange). Could I be having a spark plug wire problem that didn't appear this time because the wire is now making good contact with the plug? I'm not convinced my problem will not re-appear and I'd like to do some preventive maintenance. Any suggestions?

[jim dozier]

No suggestions other than to carefully evaluate whether you purchased the correct plug and you set the gap correctly for your particular engine. The fact that replacing the old plugs improved things makes me wonder again about the new plugs you installed.