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  1. #1

    Default mercruiser 4.3 engine won't stop

    I have a 2005 Mercruiser 4.3 190 hp in a Bayliner 185. After running for an hour or more the engine will run on after the key is turned off. Sometimes just a few seconds but often for 15 seconds or more? Dealer suggested turning engine off while still in gear but this doesn't seem to help much. Someone else suggested ignition timing may be off but it seems to run well except for getting the engine to stop. The engine has only about 20 hours. Thanks for any advice.

  2. #2
    Moderator Bondo's Avatar
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    Default Re: mercruiser 4.3 engine won't stop

    Get it back to the Dealer,+ Get it Fixed,.....

    It'll Cost you a new Motor if you Don't........

    Mercruiser has issued Service Bulletins about it......
    Any Grease is Better,..... Than No Grease at All.......

  3. #3
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    Default Re: mercruiser 4.3 engine won't stop

    Yep, timing or idle too high.

  4. #4
    Rear Admiral 180shabah's Avatar
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    Default Re: mercruiser 4.3 engine won't stop

    Quote Originally Posted by imported_Coors View Post
    Yep, timing or idle too high.
    Carbon buildup is more likely.

  5. #5
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    Default Re: mercruiser 4.3 engine won't stop

    Yep, that could do it too.

  6. #6

    Default Re: mercruiser 4.3 engine won't stop

    Has it done this since it was new?
    My volvo 4.3 did it from the start. I lowered the idle speed to 600-700 RPM,( idle speed was too fast around 850 rpm)
    and switched to 89 octane fuel. Also I always try to let the engine idle for a few seconds before shutting down. It seems to have stopped the problem.

  7. #7
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    Default Re: mercruiser 4.3 engine won't stop

    There are bullitins about this.Change gas,plugs,timing,add a carb kit, ....

    First thing I ask my customers to do is tool around the pond a bit before turning the key off,or let her idle for 2 minutes at least.Get the temp down.
    Unfortunately todays gas is made for cars,not boats.

    If your dealer is not aware of this ....... your choice

    DHP

  8. #8
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: mercruiser 4.3 engine won't stop

    Here is a copy and paste of the Mercruiser service bulletin no. 97-17

    = Revised July 1999
    Engine ‘Dieseling’ or ‘Running-On’
    Models
    MCM 4 Cylinder, V6 and V8 with Carburetors.
    Situation

    Under certain conditions, carbureted engines may ‘run-on’ when the ignition key is turned off. Normally, it
    will take a combination of several of the following conditions to make the engine ‘run on’. These conditions
    include but are not limited to:
    1. Type and formulation of gasoline available in the area.
    2. Type of boat and its engine compartment ventilation system.
    3. Outside air, inside engine compartment air and engine coolant temperatures.
    4. How quickly the engine is shut off after running at cruising or higher RPMs.
    5. How the boat and engine are operated.
    6. Engine idle rpm set too high.
    7. Wrong heat range spark plugs or spark plugs with deposits on them.
    8. Deposits in combustion chamber.
    Carbureted engines, unlike EFI, do not shut off the fuel supply to the engine when the ignition key is turned
    off. As the engine is coasting to a stop, air is still flowing through the carburetor into the manifold. This air
    flow can still draw fuel from the carburetor, through the intake manifold and into the combustion chamber.
    A hot spot in the combustion chamber will cause this fuel/air mixture to burn. The engine now ‘diesels’ or
    ‘runs on’ although the ignition system is not firing. EFI engines do not have this problem because the injectors
    do not inject fuel once the ignition key is turned off.
    Suggestion to Minimize ‘Run On’
    Items number 1 ,2 and 3 can correct or reduce most of these ‘run on’ problems. Letting any engine idle a
    minute or two before shutting it off is desirable. This helps the engine to normalize at idle rpm before being
    shut down.
    1. Be sure engine idle mixture, idle rpm and ignition timing are correct. On 4 cylinder and V6 or V8 engines
    with Thunderbolt IV ignition, setting idle rpm as low as possible can help stop ‘run on’.
    2. Adjust throttle cable barrel so that the carburetor’s throttle lever returns against the idle speed stop
    screw every time the remote control throttle lever is returned to neutral, idle.
    3. Idle engine 1 to 1-1/2 minutes before turning key off after running at cruise or higher engine rpm.
    4. Try a different brand of regular fuel or try some premium fuel.
    5. Increase idle mixture by 1/8 turn ‘richer’.
    6. Go to next colder heat range spark plugs.
    7. V6 and V8 only: Install a 140 °F(60 °C) thermostat
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  9. #9

    Default Re: mercruiser 4.3 engine won't stop

    The boat was purchased new last year. It started doing it last year after being on the water for a few times. Yesterday was first time out this year and it was pretty bad. Idleing before stopping may help, but we're skiers and it's a little impractical when skiers are down. Thanks to everyone for your help.

  10. #10
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    Default Re: mercruiser 4.3 engine won't stop

    Aren't you basically at idle picking up the skier?

  11. #11

    Default Re: mercruiser 4.3 engine won't stop

    Engine should be off when skiers are getting on board. We're in the river and trying to get them picked up as quickly as possible when down.

  12. #12

    Default Re: mercruiser 4.3 engine won't stop

    Over the past 2-3 yrs, my '97 4.3 Liter Mercruiser has had the same issue of wanting to still run after ignition turned off.

    For the 2nd time now, the motor has locked up - wont' turn over. 1st time, I stripped flywheel trying to start it. Local mechanic found water in the cylinder heads but no source of water leak - no cracks in blocks. Compression tests showed 150 on all cylinders but 140 on #3.

    Just this weekend, it locked again. I took out the spark plugs & blew water out the cylinder heads.

    The motor ran fine for the first 10 years I had it. The past 2 years, it has had the problem of continuing to want to run after shutting off key. More severe, both times that the motor has locked up.

    Any suggestions on the source or any good mechanics in the St. Paul/Minneapolis, MN area?

    Thanks,
    Mark

  13. #13
    Rear Admiral 180shabah's Avatar
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    Default Re: mercruiser 4.3 engine won't stop

    Smitty, you need to start a new thread.

  14. #14
    Moderator achris's Avatar
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    Default Re: mercruiser 4.3 engine won't stop

    Quote Originally Posted by rbrandel View Post
    Engine should be off when skiers are getting on board. We're in the river and trying to get them picked up as quickly as possible when down.
    This is something I have never understood about skiing... Why does the engine need to be shutdown when picking up a person in the water? If it's to ensure the prop isn't turning, then that's why you have a shift control... It may be a hangover from the old days when ski boats had big old V8s in them that were bolted to a propshaft, without a gearbox. I can well understand it in that situation, but the modern sterndrive does have a gearbox, use it....

    I work in the offshore industry and we are all well versed (too well versed sometimes) in emergency procedures, that includes recovering people fro the water... The first rule is NEVER shutdown an engine, especially in crowded waters, when picking up people. You need that engine running and ready to go....

    If you have just been pulling a skier around your engine has been under maximum load and the cylinder temperatures will be sky high.... THAT is the main reason it's running on... Let it idle and get the cylinder temps down....

    Chris.............
    The world takes on a whole new perspective when viewed from 100' below...



    1972 Bertram 'Bahia Mar' 20
    2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
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  15. #15
    Moderator achris's Avatar
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    Default Re: mercruiser 4.3 engine won't stop

    Quote Originally Posted by smittys5 View Post
    Over the past 2-3 yrs, my '97 4.3 Liter Mercruiser has had the same issue of wanting to still run after ignition turned off.

    For the 2nd time now, the motor has locked up - wont' turn over. 1st time, I stripped flywheel trying to start it. Local mechanic found water in the cylinder heads but no source of water leak - no cracks in blocks. Compression tests showed 150 on all cylinders but 140 on #3.

    Just this weekend, it locked again. I took out the spark plugs & blew water out the cylinder heads.

    The motor ran fine for the first 10 years I had it. The past 2 years, it has had the problem of continuing to want to run after shutting off key. More severe, both times that the motor has locked up.

    Any suggestions on the source or any good mechanics in the St. Paul/Minneapolis, MN area?

    Thanks,
    Mark
    A. Start a new thread
    B. I bet the manifolds and elbows are original, yes?

    Chris...........
    The world takes on a whole new perspective when viewed from 100' below...



    1972 Bertram 'Bahia Mar' 20
    2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
    **
    Please don't send service questions in private messages. That's what the forum is for. Messages of thanks, always accepted.
    **
    Member of the month - April 2013. http://www.iboats.com/blog/achris-member-of-the-month/

  16. #16
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    Default Re: mercruiser 4.3 engine won't stop

    Quote Originally Posted by achris View Post
    This is something I have never understood about skiing... Why does the engine need to be shutdown when picking up a person in the water? If it's to ensure the prop isn't turning, then that's why you have a shift control... It may be a hangover from the old days when ski boats had big old V8s in them that were bolted to a propshaft, without a gearbox. I can well understand it in that situation, but the modern sterndrive does have a gearbox, use it....

    I work in the offshore industry and we are all well versed (too well versed sometimes) in emergency procedures, that includes recovering people fro the water... The first rule is NEVER shutdown an engine, especially in crowded waters, when picking up people. You need that engine running and ready to go....

    If you have just been pulling a skier around your engine has been under maximum load and the cylinder temperatures will be sky high.... THAT is the main reason it's running on... Let it idle and get the cylinder temps down....

    Chris.............
    Couple of reasons. First of all, the reason that you mentioned. You don't want to accidentally knock it into gear while someone's climbing up the drive. I'll wager that in most crowded water rescue situations, it's not routine for people to be climbing up on/behind the drive.

    Secondly, it's just a bad habit to have an engine running near anybody in the water. Carbon Monoxide collects on the surface of the water, right at face-level for people in the water. It's not so much a big deal for quick pick-ups, but for simplicity's sake, loading and unloading of passengers should ALWAYS be done without pumping poison onto the surface of the water.

    Skiing in highly crowded areas is also ill-advised.

    Rescue situations are going to be a bit different--especially when making guidelines for professionals vs. weekend warriors. On a rescue boat, everybody's got a job, and a place where they're supposed to be. The pilot's not likely to be standing up to hang wakeboards on racks, handing people towels, or anything else that's likely to distract him from his job. Unlike quite a few people I've boated with.

    Hell, CPR has completely done away with vitals checks before going straight to chest compressions, and there is no longer any rescue breathing involved.

    You can bet your butt that BOTH of those steps are SOP for medical professionals, however. I'll continue to stick to the vitals check/rescue breathing.

    I'll also continue to load and unload riders with the engine OFF.

    Both are, to me, just common sense.

  17. #17
    Petty Officer 2nd Class
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    Default Re: mercruiser 4.3 engine won't stop

    i've only just done my RYA (royal yachting assoc) international certificate of competence.

    Man over board was ofcourse something covered in the instructing and test, also during skiing it was always stressed to turn engine off whenever near someone in the water or recovering a man over board to minimise the risk of accidentally engaging the prop, in man overboard the engine should be turned off once contact has been made with the man overboard.

    What i see here in spain is that boats are always loaded with kids, i would rather have the engine off instead of run the risk of having a kid chop me up whilst playing with that `funny lever dad always plays with´
    2001 crownline br 205
    4.3 EFI mercruiser
    Spain

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