Irregular idle

[jimhen]

I have a 1986 Mercrusier 2.5
I have experienced this as a reoccurring problem, I just tuned everything up and she runs out nice ( except ) ....
If I have been running with speed.... 3000 RPM to WOT and throttle down, let's say to pick up a skier... I get an idle at abt 1100 to 1200 RPMs sometimes (if) I can bump it back in gear it drops back down to where I have it set abt 600.
Another problem occures when I come in to dock, sometimes it falls off the 600 at idle and sputters then dies ( usualy at a very inconveinent time) generaly when droping into neutral and often wanting for some reverse.

I rebuilt the carb a couple of seasons ago and that fixed some other issues... is this maybe an distributer advance problem.

PS : this is one of those happy intermittent things that doesn't hapen every time around.

 

[Bondo]

Re: Irregular idle

My 1st Guess would be either the Carbs Idle Circuit,.....
Or the Cable/ Linkage to the Carb is the Problem...........

 

[Don S]

Re: Irregular idle

Sounds like you have more than one issue.
The carb not going to idle is probably the cable adjustment. Disconnect the cable from the carb. The cable should just preload the linkage to the idle possition. Adjust the cable barrell to get it.
Other idle problems could be ignition. When was the last full tune up? Points, condenser, cap, rotor, sparkplugs, dwell, timing, advance timing, mixture adjustment etc. It all has to work together, not just carb.
A possible problem with it dieing when going to neutral is likely a lower shift cable. When they start binding (corrosion and age) they hold the shift interrupt system on to long and it kills the engine. Replace the cable.

 

[jimhen]

Re: Irregular idle

I had just replaced and tuned up everything, short of the mixture adjustment on the carb. I had a friend rebuild it for me a couple of years ago, but I do not have much carb experience.
You both have mentioned the cable adjustment , are you talking the throttle shift cable that runs from the console?

I will also check the cables... for the most part the boat is very clean it has just seen fresh water and a short season in upstate NY. Could the problem with it falling off and dieing be due to fouling the plugs? we have a long run in to the landing that is no wake... about 1 to 1/12 miles.