Evinrude 150 idle trouble

[Lighthouse]

I hope someone here can help me out. My 1992 Evinrude 150 recently started idling around 1100 -1200 RPMs, ( no load ). I checked everything my shop manual said to check, ie: vacumm leak, timing, Quickstart circuit, temp sensor, throttle lever and cable adjustments, etc. The only thing that is not checking out is the Quickstart circuit. When I first start the motor when warmed up it revs up to 1200 RPMs, then in about 5 seconds it drops to around 900 RPMs, but then slowly increases back to around 1100 RPMs. I initially thought the Quickstart was working because of the RPM drop, but upon checking with a timing light there was not any timing change. Even when pulling the temp sensor connector there was not a timing change. However, the timing is currently at 9 degrees ATC, so it is already retarded further than it should be and would only idle higher if I advance it to the recommended 6 degrees ATC. Also I have sprayed around all the intake gaskets and vacuum hoses, and can not find any evidence of a vacuum leak. So does anyone have any ideas of what might be causing my problem. I'm trying to avoid having to take it in to a shop if I can take care of it myself. Thanks for any help you can provide.

 

[Solittle]

Re: Evinrude 150 idle trouble

Lighthouse - I don't know squat about your motor but I have never heard of a timing setting at ATC. You might verify.

 

[Sand Bass]

Re: Evinrude 150 idle trouble

Lighthouse, I would do a "link-n-synch". Make sure that all throttle plates are COMPLETELY closed when in neutral. If one or more of them are slightly cracked open it will cause engine to idle fast. Sometimes they can be cracked ever so slightly and you cannot tell by looking at them or tapping on them (happened to me). My manual shows idle timing for your motor to be 5-7 degrees ATDC. <br /><br />Good Luck