4.3 merc runs on @ shut down

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greg baranitsky

Cadet
Joined
May 17, 2003
Messages
22
I've got a 2000 Sea Ray with a merc 4.3 that likes to run-on when you go to shut her down. I've put new fuel in her and still have the same problem. Not to sure of what to look for! Maby someone here will be able to help? :confused:
 
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Skinsk

Petty Officer 2nd Class
Joined
Aug 31, 2003
Messages
128
Re: 4.3 merc runs on @ shut down

Mercury put out a service bulletin on this problem. Can't remember it verbatum, but it basically said to <br />-Let the motor idle for a bit before shutting it off<br />-Use a higher octane fuel<br />-Make sure the timing is set correctly<br />-Make sure the carb idle mixture is set correctly, and it may be necesary to richen up the mixture a bit.<br /><br />I think that's it, but there may be more..<br /><br />Scott.
 
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BrianFD

Senior Chief Petty Officer
Joined
Jul 30, 2003
Messages
748
Re: 4.3 merc runs on @ shut down

What Skinsk says is true. I, too, have a 4.3 Mercruiser and it used to run-on until a boat mechanic told me to let her idle about 2 minutes before shutting down. Two minutes is what it takes, too. Even a 1.5 minutes, she'll diesel. what concerns me most is what would I do if I had to shut down immediately in an emergency. Don't have the answer to that...<br />Happy Boating!<br />Brian
 
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Skinsk

Petty Officer 2nd Class
Joined
Aug 31, 2003
Messages
128
Re: 4.3 merc runs on @ shut down

I think if you shut down in an emergency, and you were in gear, the motor would quit. A dieseling motor is uaully only just barely running, so any sort of drag, such as the being in gear, would kill it.<br /><br />Scott..
 
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Puffdragon

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Joined
Sep 4, 2003
Messages
12
Re: 4.3 merc runs on @ shut down

One cause of dieseling can be a carbon buildup on and around your valves that gets really hot and basically causes ignition even when your plugs are no longer sparking. This can occur after extended hard usage and is the reason you should idle your boat for a while before stopping it.<br /><br />To take care of this use a higher octane of quality gas to prevent deposit buildup and possibly run a good fuel treatment through the gas to help burn off the deposits that are there.
 
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greg baranitsky

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Joined
May 17, 2003
Messages
22
Re: 4.3 merc runs on @ shut down

Thanks for all the input guy's.. :D I'll take a look at it this week when I get some time. :)
 
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p sully

Cadet
Joined
Jul 8, 2003
Messages
24
Re: 4.3 merc runs on @ shut down

The advice you are getting about allowing the 4.3L to idle for a couple of minutes in a 2000 Sea Ray is right on. I have the same problem with my 4.3 in a 1998 Sea Ray. I love the engine and the boat. Handles great,always starts,but letting it idle before turning the ignition off is a must or run on is inevitable.A small inconvenience for such a great engine and boat.<br /><br />P Sully
 
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BrianFD

Senior Chief Petty Officer
Joined
Jul 30, 2003
Messages
748
Re: 4.3 merc runs on @ shut down

Thanks, Skinsk! I printed out that service bulletin & placed it with my boat documents! Good job!<br />Brian
 
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