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Old 05-08-2007, 10:30 PM   #1
Join Date: Nov 2006
Location: Richmond, KY
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Default Beffudled with engines

Took the family out Sunday for a few hours. It was great!! About 85, no clouds in the sky. Spent about 2 and 1/2 hours out on the water, just piddling around.

Anyway, I had previously posted about the engine having an occasional backfire. Well, not a single backfire. I'm thinking that maybe something was wrong with the fuel. Who knows. I was hoping to do a little trouble shooting but didn't have to.

So here's what did happen. The second time I shut down the engine, it had some run-on. But that was the only time it happened. I shut it down four other times and no run-on. I remember someone posting about that problem before, but can't remember who it was.

I've got the 190 hp 4.3. Anyone have the run-on issue and did you experience it all the time or did it come and go? Also, is there always some kind of problem to deal with?

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Old 05-08-2007, 11:15 PM   #2

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Join Date: Nov 2005
Location: Everett Wa
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what your experiencing is dieseling....very bad on a water borne engine since it can suck water into the piston thru the exhaust....usually happens when your running hard and haven't had a chance to cool the engine down at idle speed..'s what you that the points gap/dwell are within specs if you have them....make sure the plug gaps are correct....then start the engine either in the water or on muffs...check the timing....if your not set right..the engine will either diesel or back fire thru the carb
.adjust the carb on the idle each one all the way in till they just seat...then back them out 1.5 turns...don't know what engine you have so I'm assuming it's a SBC ...blip the throttle a few times to get it to settle down...adjust the idle mixture till the engine runs smooth..don't keep turning them out...once it goes from running a little hard to smooth..that's it....then adjust the idle speed to about 600rpms....that's it...unless you have bad gas..then run it out and add new gas......hope this helps....

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Old 05-09-2007, 02:29 AM   #3
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I've made a few posts about my 4.3 with it's trademark diesling "issue". With only 55 hours on my 1 year old 1800 SR-3 I still have diesling. Dealer has looked at it twice and said all is fine. Let her run for at least 30 seconds before you shut her down. It sucks if you do a lot of water sports and need to pick someone up quick. It's hard to tell a tired 13 year old they need to relax for a minute while the engine idles with boats bearing down on them. Diesling sucks. Literally. :wink:
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Old 05-24-2007, 03:11 PM   #4
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My 4.3 190hp 1800 SR3 also dieselled when I first got it. Have since got to know an ex tech specialist for the Mercruiser sole importer here in the UK who assisted Merc dealers in the UK with technical problems they were unable to resolve themselves. He said the standard and quickest way to significantly reduce (but probably not completely eliminate) this issue is to swap down from a 160 deg to 140 deg thermostat so the engine runs a little cooler. He did that to mine and it hasn't completely stopped it but reduced the number of times it happens by 75% I'd say.

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