Merc 43overrun

hello...some advice please ...

hello...some advice please ...new carb...runnin ok but on ignition shut down continues running for up to 10 seconds....too rich maybe...

"Too Rich,.....
Or,...
The T

"Too Rich,.....
Or,...
The Timing is Too Advanced,.....
Or,...
There's Carbon deposits on the pistons causing Run-On.....

Whatever it is,.... Ya Gotta Fix It.....
If you Don't,....
It'll draw Water into the cylinders,+ Hydro-Lock the motor......"

"If the boat is from about 199

"If the boat is from about 1997-1999, they had a service bulletin about this issue and I listed all of Mercruiser's suggested steps in another thread. If you call a Mercruiser dealer, ask for a copy of bulletin 97-17 dated July 1999. They probably won't know anything about it because most dealers don't read the bulletins and at this point, I doubt if many techs or service managers will go back and read old bulletins. For that matter, when I called Mercruiser for a copy of it, the new guy in the technical department didn't know about it, either. I asked how long he had worked there and when he said it was a few years, I told him to ask one of the old timers about it.

Running rich will definitely cause this, along with running it hard and shutting it off without letting it cool down. Engine compartment not being ventilated well will contribute, too, since the compartment temperature will be higher than what the motor likes."

A little more info please.

A little more info please.

Did it just start happening all of a sudden? Has it been there a while getting worse? Did you just buy the boat? Did it only start when you installed the new carb but otherwise it was fine before? When did you last change the plugs? Are they the approved type? How long since youve had the heads off?

Sorry to ask so many questions but it will help a lot in trying to dertermine what could be causing your problem.

There are a number of things can cause this problem in petrol engines.

"David, My '88 4.3LX alwa

"David, My '88 4.3LX always did that after a hard run. The cure was to let it idle for 30 seconds, prior to shutting it off. Another method was to shut it off in gear."

"Shutting it off in gear works

"Shutting it off in gear works but if the run-on is caused by hot spots, it can have problems later and it'll be hard to pinpoint the cause. Better to let it cool naturally and then shut it off. Actually, it would have been better if Merc had taken care of the problem before shipping the hundreds and thousands of motors out with this problem. Everything they recommend is just band-aids.

David- get the bulletin and see what you need to do. Worst case, you may need the throttle solenoid kit, which is expensive and a cheap mechanical alternative it possible. The solenoid just closes the throttle plate completely to choke the motor. How old is your impeller? If that's not doing its job, the motor will run hot and this can happen. If the motor runs backward at the end of the run-on and ingests water, it won't crank at all and if you keep trying to crank it, you'll kill your starter. You'll need to pull your spark plugs and crank it. If the motor is hot enough and water gets into the cylinders, you can damage your valves and pistons (cold water + hot metal = trouble)."

what is your idle rpm ? 4.3 r

what is your idle rpm ? 4.3 really like to keep running if above 650