Engine running on?

[SkippersMinnow]

Had my boat out a few times and noticed the engine "runs on" on occasion, so I called the dealer. He said to let it idle a minute or two and then shut it off. I tried this the next time out and it still did it. So I had my 20 hour check up done, and I told them it was still running on when I turned it off. They told me they turned down the idle and it should be fine. I then had it with me on a weeks vacation, and now it idles at 550 rpm, idles real rough, and STILL runs on from time to time? It is a 2001 3.0L mercruiser with an Alpha 1 sterndrive. Any others with the same problem? I was asked if I was using regular gas, and I said yes. Do any of you run mid grade or premium?

 

[gary fluke]

Re: Engine running on?

My Mercruiser 4.3 Alpha One runs-on when I turn the engine off right after coming off of a plane. I do run regular gas, 87 octane. If I run slowly for a bit, it doesn't run-on after shutdown.

 

[Trent]

Re: Engine running on?

Skipper..Try higher octane fuel. That works most of the time. Did you have them check the timing? Make sure to get this fixed. Run ons can lead to sucking water in thru the exhaust and ruining the engine.<br /><br />By the way Mary Ann!

 

[flashback]

Re: Engine running on?

run on is commonly refered to as dieseling and it can be a combination of things but in most cases it is spark timing or bad gas......

 

[gsnyder]

Re: Engine running on?

Skipper--I have a Volvo 4.3L, which requires mid octane gas. I inadvertently put 87 octane in it for a couple of gas cycles, and had a dieseling problem. 89 octane cleared up the problem, and the dieseling has not occurred since.

 

[bowriderbob]

Re: Engine running on?

Skippers,<br /><br />I've got the same engine setup ,and had similiar problems dieseling. I've learned to either use octane booster additive with a fill up or premium gas. I also try to let it idle for a minute or so, before shutting it down. Most of the time that stops it from dieseling.<br /><br />Bowriderbob<br />99 VIP 184<br />3.0 L Mercruiser

 

[postjim]

Re: Engine running on?

Same Problem. Went to 89 octane which significantly improved the situation.

 

[robwingo]

Re: Engine running on?

I got the same problem with my 2002 4.3L. I found the following Mercruiser service bulletin: <br /> http://www.bravodrives.com/GasolineService/Bullet/97/97_17.pdf My service guy adjusted the carb, but I am having other problems which I think (hope) are bad gas.

 

[Slimmer]

Re: Engine running on?

Have to agree with flashback, usally improper timming will cause " run on"

 

[akriverrat]

Re: Engine running on?

improper timing because it causes overheating and/or hot spots in combustion chamber. same with low octane fuel. increase octane and keep top end power or retard timing and lose some.

 

[toddbsss]

Re: Engine running on?

I'd have to agree 'run on' leads you to a ignition timing problem, try running some combustion camber cleaner through your engine,there are many products available.Carbon build ups in your cylinder can cause hot spots which will try to refire the engine 'run on'. Try the easy way out first run a couple of tanks of premium fuel through first. Good luck!

 

[akriverrat]

Re: Engine running on?

often it is an idle mixture problem. instead of adjusting mixture and idle speed to get throttle plates closed enough to prevent run on the idle speed screw just gets turned in, increasing idle speed and covering up slightly off mixture.