OMC engine issue

Alan1h

Recruit
Joined
Sep 2, 2008
Messages
2
I have a OMC 3.0L Cobra, 1989, Jasper rebuilt with 100hrs. this year.
Ran great... still does with this one issue.

Starts and idles at 600RPM but after running and bring it back to the dock...
I slow it down to go into neutral and it jumps to a fast idle at approx 1200RPM which doesnt make it much fun to try and dock!

I also Pertronix electronic ignition conversion.
New plugs and timing checked.

If I turn it off and start it back up, it idles at 600rpm again.

Any ideas???

Thanks,
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: OMC engine issue

You probably need to adjust the throttle cable so it slightly preloads the carb linkage to the idle position.
 

subcrx

Petty Officer 2nd Class
Joined
Sep 3, 2007
Messages
197
Re: OMC engine issue

did you try overriding the throttle linkage to the carb?
 

Alan1h

Recruit
Joined
Sep 2, 2008
Messages
2
Re: OMC engine issue

Overiding the throttle linkage? I'm not sure what you mean...
 

subcrx

Petty Officer 2nd Class
Joined
Sep 3, 2007
Messages
197
Re: OMC engine issue

Disconnect the throttle linkage from the carb. close it by hand and see if it goes down
 

MBAKER

Petty Officer 1st Class
Joined
Jun 9, 2008
Messages
279
Re: OMC engine issue

does it idle slow when cold, then as soon as everything comes up to temp the fast idle shows up?

If so could be the idle speed is just to fast, all engiens will idle a little faster as they warm up. So even though the idle speed is correct when cold, once it warms up its too fast. May just need to be readjusted after the boat is warmed up and running, and then when cold you may have to put on fast idle in neutral to warm it a little before heading out.
 
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