Is it normal for Merc 3L I/O to run on when turned off?

[chrisg]

I have a 2003 bayliner that has always 'run-on' if I turn it off after towing the kids on tubes. It's a reall pain to tell the kids to tread water while the engine 'chuggs' until it finally stops.<br /><br />The dealer said it is normal, I have to give the motor a few minutes to idle befor turning off. How long do I have to wait!<br /><br />Some say it is not normal to do that, others say that is a normal for engines with carberators. What adjustments can I make myself to try and reduce the issue? The thing also stalls at times when I open the throttle quickly. ( IE trying to pull up a skier). The guage says the engine temp is 176F. If I take it to the dealer, there is no water for him to test it out on. ( there is not much (boatable) water in this State.)<br /><br />Ideas?

 

[Trent]

Re: Is it normal for Merc 3L I/O to run on when turned off?

Mercrusier put out a service bullitin about this several years ago. Basically said to try higher octane fuel, run blower more, and to let it idle a few min before shutdown.

 

[texsun]

Re: Is it normal for Merc 3L I/O to run on when turned off?

I agree with Trent. My 3.0 would run on. I changed to midgrade fuel and the problem disappeared.<br /><br />Give it a try. Good Luck!

 

[crazy charlie]

Re: Is it normal for Merc 3L I/O to run on when turned off?

If all else fails you can turn it off while in gear and it may not chug that way.Charlie

 

[johnholt]

Re: Is it normal for Merc 3L I/O to run on when turned off?

I had the same problem on my 2003 3.0. The dealer checked it out, and nothing got any better. I hooked up my own tach, and found out the stock tach was reading 800 rpm, and my tach read 1000 rpm. I lowered the idle to 800 on my good tach, and now 30 seconds to a minute is all I let it idle before shutting it down, and the 'run-on' problem is fixed.

 

[MFG197]

Re: Is it normal for Merc 3L I/O to run on when turned off?

Same here with 5.7LX, run on seems to be more prevelant when 87 octane is used (fine according to owners manual) and engine is shut down hot. I run blower when coming down from speed and let engine idle a few minutes and I use 89 or 92 octane.

 

[Invader92]

Re: Is it normal for Merc 3L I/O to run on when turned off?

I also have a 3.0 I/O Merc but I dont that issue. Lucky I guess.

 

[BMDODGE]

Re: Is it normal for Merc 3L I/O to run on when turned off?

i don't hve the problem either... i use super unleaded for fuel ( ouch $$$ ) plus i set my idle very low... Bruce

 

[Blk-n-Blu]

Re: Is it normal for Merc 3L I/O to run on when turned off?

here is a link to Merc service bulletins for anyone who wants it<br /> http://www.boatfix.com/merc/Bullet/sbcover.pdf

 

[chrisg]

Re: Is it normal for Merc 3L I/O to run on when turned off?

Thanks all, <br /><br />I will try a tank of super unleaded ( have to cart it in 5 gal. at a time). Sounds like this does not hurt the motor. I did try turning on the blower, and it did help. ( Didn't 'chug' as long, or it turned off right away).<br /><br />I'll let you know.<br /><br />CanadianInIowa

 

[BMDODGE]

Re: Is it normal for Merc 3L I/O to run on when turned off?

be sure to check your timing and dwell (point gap) it could be to far advanced which would also cause run-on...

 

[mikegrant]

Re: Is it normal for Merc 3L I/O to run on when turned off?

I have observed this problem on occasion with my 3.0....<br /><br />I try to use non-oxygenated fuel at all times (typically it is the rated 92). When I end up purchasing oxygenated fuel I usually get the lower octane stuff...87 or 89. <br /><br />The run-on appears more frequently when I purchase the oxygenated lower octane fuel....<br /><br />I wondered if it was a condition specific to my boat or more common....<br /><br />good luck...it is iritating!!

 

[chrisg]

Re: Is it normal for Merc 3L I/O to run on when turned off?

Update:<br /><br />The higher octane stuff did not help ( the regular is 87, the ethonal is 89, an the super is 91). <br /><br />I have sent my boat in to a different Marina to check it out. They say the normal gas is good enough. I also know someone else with the same boat ( only a '99) says he has the same issue. He also indicated that he has another friend who has the same bayliner, and it does it too. He said give up and live with it.<br /><br />Do other i/os do this? is it only Mercs?<br />( then I will not buy a Merc again!)<br />I'l

 

[tommays]

Re: Is it normal for Merc 3L I/O to run on when turned off?

i have a 1995 3.0 merc and have always used 92 or 93 and have never had afterrun it is going to take some time for a better fuel or engine cleaning stuff to remove the carbon deposits that are staying hot enough after the key is turned off to keep the engine running i would try to get it cleared up because it is not great for the motor and not as safe as haveing the motor stop when you want it to<br /><br />tommays<br /><br />tommays

 

[surfer23505]

Re: Is it normal for Merc 3L I/O to run on when turned off?

Sorry for the earlier rude comment.

 

[John Carpenter]

Re: Is it normal for Merc 3L I/O to run on when turned off?

Surfer23505...what a tremendously helpful and insightful post. Too bad you only have 4 to your credit. Wisdom like that is probably wasted on the crew around here...why don't you find a forum where you would be more appreciated...surely some board is in need of a five year old.

 

[BMDODGE]

Re: Is it normal for Merc 3L I/O to run on when turned off?

dito

 

[fishhunter911]

Re: Is it normal for Merc 3L I/O to run on when turned off?

Try adding some decarb to you tank and run that through. Might help some. I had the same issue and ran a tank of 93 octane and some decarb. Havent had the run on since. I have a 2003 Wellcraft with the 3.0L.

 

[Northern Eclipse]

Re: Is it normal for Merc 3L I/O to run on when turned off?

BMDODGE... I stand corrected, go back to surfers post. C.I.I 176f temp is a bit warmer than 140 for water temp not bad though, but internal temps will be greater, Give her a cool down period before shut down, and maybe consider doing impeller. I think your temp is a early warning towards impeller failer, How many hours on your boat?

 

[kcole683]

Re: Is it normal for Merc 3L I/O to run on when turned off?

surfer23505 <br />Member # 46247 posted July 20, 2004 11:20 PM<br />--------------------------------------------------------------------------------<br /> Bayliners are cheap and crappy boats! Buy a decent boat tightwad! <br />

That is a totally unecessary comment surfer.<br />What does a Bayliner have anything to do with a screwed up Mercruiser in the first place??<br /><br />Mom always told me "If you can't say something helpfull then keep your mouth shut".<br /><br />Good advice I would say.<br /><br />As for the problem with the 3.0 Mercruiser there is alot of good info in the posts here. Keep your engine compartment as cool as possible,make sure timing is not over advanced etc. Check the engine temperature with an acurate thermometer to make sure cooling is up to snuff.<br />Does that engine have a 145 degree t-stat in it? If so then 176 degrees sounds plenty warm to me. The stat should be wide open at 160 degrees or so.<br />Good luck