1992 Mercruiser 3.0L throttle/idle problem.

[onesweetworld]

Hello All,

Took the boat out today and it was running great. Drove about 6-8 miles without stopping. Some throttle up and down but nothing crazy. At the end of the trip as I was throttling down to come into the harbor, I had noticed that at idol the RPMs were still high (about 20K) and the engine also sounded to be idling high. Eventually I opened up the engine compartment and backed the idol screw back a turn and a half to a point where the RPMs were down below 10K and the engine was sounding normal for it being at idol.

Any insight as to why this event may have occurred or what could be wrong? I don't believe that the idol screw tightened itself in a turn and a half after driving such a short distance. My action to back the idol screw out was just a band aid fix to prevent the drive from slamming into gear until i could get back to the dock and figure out the real cause of this high idol situation


1992 Sea Ray. Mercruiser 3.0L Alpha1 Gen. 2

Thanks is advance!

 

[alldodge]

Is this a new to you boat?
If not, how long have you had it, what has been done to it this season?
Filters changed?

 

[onesweetworld]

I have owned this boat since 1992. Regular maintenance done. Oil and filter, fuel filters, plugs, ran sea foam through a few fill ups ago Fuel is new. No work on the carb this year.

Not that i think this has to do with the problem but alignment check this year as well and new out drive gaskets and lower gear oil changed. I just cant think of what could have changed with the throttle/idol setting from all the times out this season...

 

[AlabamaNewbie]

When is the last time you checked the adjustment of your electric choke?

 

[achris]

Check the timing. If the timing has advanced, your idle speed goes up. I think you mean 2k and 1k, not 20k and 10k. Not even F1 engines run that fast. :lol::lol:

 

[alldodge]

I have owned this boat since 1992. Regular maintenance done. Oil and filter, fuel filters, plugs, ran sea foam through a few fill ups ago Fuel is new. No work on the carb this year.

Not that i think this has to do with the problem but alignment check this year as well and new out drive gaskets and lower gear oil changed. I just cant think of what could have changed with the throttle/idol setting from all the times out this season...

Thanks much

In that case I would check for play/slop in the throttle control and cables. While the idle did reduce when the idle screw was turned, I'm wondering if the pressure against the stop was the same. Suggest getting it warmed up and idling as it should, then grab the carb butter fly and see if you can pull it further closed to reduce idle further.

Next check for a vacuum leak