motor running on tooo long?

Mark RSA2AU

New Member
Sep 21, 2009
62
Melbourne
Boat Info
Sea Ray 180
Wakeboard tower
Engines
3.0lt Mercruiser
Hi Guys

I have in the passed discussed this issue but have been unable to solve it, so my questions are will this do dammage to the motor, and can anyone think of another solution.

I have a 1999 Sea Ray 180 with a 135 hp 3lt Mercruiser and Alpha 1 leg. The motor frequently runs on after the ignition has been turned off, some times for over a minute, even after allowing it to idle for a minute or two.

I have had it serviced, and lowered the idle speed to just above stalling, which it now does painfully often and does not idle properly when cold.
I have used hotter and colder spark plugs ( now using Irridum tipped), better but not stopped.
I have used a fuel system cleaner which is also supposed to remove carbon deposits.
I have tried different fuel grades, changed the air filter ( K&N), fuel filter ( Merc)....
and I have danced around the boat in small circles ( after I burned my hand)

And still I cannot stop the motor running on.
This is especialy irritating when out sking as I do not feel it is safe to clime aboard untill the motor stops.

So will it dammage the motor or should I continue to look for a solution???

Cheers
Mark
 
I never had a hint of run-on in eight years owning my 3.0, and I ran the lowest octane fuel available - 87 (R+M)/2.

I think you said the prop keeps turning? Run-on should never make enough power to do that, and therefore I suspect you have an ignition system issue. The spark plugs are still getting spark from somewhere. Perhaps you can get a timing light to check for spark.

If you are sure the ignition is off, has the engine been modified for higher compression? A compression test should show if that has ever been done. Does the engine ever ping under load? Possiby the fuel you are getting is low-octane and prone to detonation. Is higher-grade fuel available? Try it, or possibly try a different source for fuel. You could be getting lower-octane fuel than your engine needs.

Good luck!
 
Hi Mark,

We do a lot of wakeboarding with our Sea Ray, which requires a lot of stopping to either put folks in the water, or retrieving them from the water. I have found that the only thing that helps with this problem for me, is to put it in neutral, and idle for about 1 minute, and then shut it off. Any other remedy did not work. Granted, I have a 5.0 V8, but the principles of this (some call it pre-ignition or dieseling) seem to be the same: rapid deceleration followed by a shut down make the engine want to continue running. Allowing the engine to idle to clear things out makes all the difference for us. I realize that you said you have tried this already, but give it a try again, making sure that you wait for a full minute, at least.

And now, for some worthwhile reading from Merc:

http://www.4shared.com/file/53242775/d72d01/Engine_Dieseling_or_Running_on.html

Good Luck!
John
 
Last edited:
There are two things that you didn't mention trying in your message:

1-If your ignition timing is too far advanced, it can cause engine run on. Running fuel with higher octane is supposed to compensate for this situation somewhat. You could try to speed your idle up to a reasonable RPM and then retard your timing by turning the distributor in the same direction of the normal rotor rotation. You do this by loosening the hold down clamp under the distributor. This should slow your idle speed slightly as well and you may have to turn it up again.

2-Excessive carbon build up on the piston top or combustion chamber may be allowing the unburned fuel / air mixture to ignite without the engine ignition system operating. The top end of your engine would have to be cleaned in this case. I don't have any experience with liquid top end cleaners to recommend.
 
Idling after coming off plane has helped me minimize run-on especially when I have the blower running.
 
Hi Guys

I have in the passed discussed this issue but have been unable to solve it, so my questions are will this do dammage to the motor, and can anyone think of another solution.

I have a 1999 Sea Ray 180 with a 135 hp 3lt Mercruiser and Alpha 1 leg. The motor frequently runs on after the ignition has been turned off, some times for over a minute, even after allowing it to idle for a minute or two.

I have had it serviced, and lowered the idle speed to just above stalling, which it now does painfully often and does not idle properly when cold.
I have used hotter and colder spark plugs ( now using Irridum tipped), better but not stopped.
I have used a fuel system cleaner which is also supposed to remove carbon deposits.
I have tried different fuel grades, changed the air filter ( K&N), fuel filter ( Merc)....
and I have danced around the boat in small circles ( after I burned my hand)

And still I cannot stop the motor running on.
This is especialy irritating when out sking as I do not feel it is safe to clime aboard untill the motor stops.

So will it dammage the motor or should I continue to look for a solution???

Cheers
Mark

Mark, I have the same power package in my 2006 175 and have had the same issue.

The dealership (Master dealer) was not able fix it after three attempts so I paid my marina mechanic to look it and he found that it was badly out of adjustment from factory specs. The engine runs a lot better since being put back to factory specs.

That being said, the engine will still occassionally continue to run after turning off the ignition (I believe the term for this is 'dieseling') but only if the engine is hot from skiing or tubing and I haven't let it cool down for 30 seconds or so before shutting it off.

Try running your blower and letting the engine idle for 30 seconds or so before shutting it down, and if everything else is adjusted correctly (timing in particular!) that may solve your problem.

Jeff
 
Hi Guys

I have in the passed discussed this issue but have been unable to solve it, so my questions are will this do dammage to the motor, and can anyone think of another solution.

I have a 1999 Sea Ray 180 with a 135 hp 3lt Mercruiser and Alpha 1 leg. The motor frequently runs on after the ignition has been turned off, some times for over a minute, even after allowing it to idle for a minute or two.

I have had it serviced, and lowered the idle speed to just above stalling, which it now does painfully often and does not idle properly when cold.
I have used hotter and colder spark plugs ( now using Irridum tipped), better but not stopped.
I have used a fuel system cleaner which is also supposed to remove carbon deposits.
I have tried different fuel grades, changed the air filter ( K&N), fuel filter ( Merc)....
and I have danced around the boat in small circles ( after I burned my hand)

And still I cannot stop the motor running on.
This is especialy irritating when out sking as I do not feel it is safe to clime aboard untill the motor stops.

So will it dammage the motor or should I continue to look for a solution???

Cheers
Mark


Mark,

Does your engine have a carb or is it fuel injected?

-John
 
Wow. Very old school problem here. I’m having flash backs of the glowing lead deposits in the combustion chambers.

Here’s how that was stopped in the 70's. A little idle stepper solenoid was fitted to the carb. The engine idled off this sol. When ign shut off, so did the sol. and the butterfly’s shut. No fuel, no run on.

What’s setting off the run on is most likely glowing oil deposits. Your most likely pulling oil down from your intake valve guides.

God I miss my 67 Toronado, 425ci. I could run in for six, come out and never use the starter to get her going again. ...Ron
 
That's why I am asking the question of carb versus fuel injection.

If it is a carb, an idle control solenoid probably can be fitted which might significantly reduce the "run on" problem. As Bonbini noted this cuts off the air supply. The heart of the issue is the combustion chambers are very hot and continue to ignite fuel/air drawn through the carb. If the carb is open....the cycle continues until the cylinders cool down.

This needs to be addressed because this type of detonation can be damaging to the engine since cylinders fire at random and sometimes together.

If this is fuel injected, something is really wrong since the fuel injectors are controlled by an ECM.

-John
 
Hi Guys

Thanks for all the replys. Yes I do idle the motor before shut down, normaly for a minute or two. Or I idle slowly back to the skier so as not to screw up the water, so the motor has time to cool off a little. I run a standerd grade fuel, not the premium or the cheapest ethenol blend we get, but fuel grade makes no difference to the running on.

I have had the carb stripped and cleaned and the compression seems to be in normal range, as is the timing. I have also run a decarbonising aditive into the fuel to try and clean out any carbon deposits.

I might take it to the workshop to be checked again if this is going to cause dammage.

Thanks Again

Mark
 
I had an old Corvette in the 70s that used to run on. I'd just put it in the top gear and let the clutch out. What does your boat do when you shift it into gear with the ignition turned off?
 
Is there a concern with the engine sucking in water with this condition?
 
Is there a concern with the engine sucking in water with this condition?
Extremely good point here. When a gasser gets to dieseling, its not all that uncommon for one to run backwards for a bit just before they die. That would not only draw in from the exhaust, but spit out gas/fumes out the flame arrestor. Boom! ...Ron
 
Hey guys

I have tried to push it into gear after the ignition is turned off and it is running on. This does seem to shorten it a little but I was concerned about the gearbox being dammaged.

Had not thought of the motor sucking in water from the exhaust. I did not think the water joined he exhaust close enough for this to happen. But the fire risk is a concern!

Thanks again
 
Here is a old school method.
Let me see if I can say this properly so no one misunderstands.

Get the engine hot "Normal running temp" , run up the RPM's in N to about 1200 to 1300 and as it's running, using a spray bottle like a Windex or pet misting bottle on fan or atomizing spray.

Spray water into the carburetors till the engine runs very rough. The engine must be hot to do this. What it does is the steam rapidly expands during detonation and blast all the carbon out of the combustion chamber. It may need to be done several times to get it all out.

This was the method back in the days of led, points and carbs in my grandfathers ESSO station.
 
I'll defer to experts on this subject, but in regards to "could it cause damage"... Would lack of oil supply be a concern? Due to limited RPM's.
 
Here is a old school method.
Let me see if I can say this properly so no one misunderstands.

Get the engine hot "Normal running temp" , run up the RPM's in N to about 1200 to 1300 and as it's running, using a spray bottle like a Windex or pet misting bottle on fan or atomizing spray.

Spray water into the carburetors till the engine runs very rough. The engine must be hot to do this. What it does is the steam rapidly expands during detonation and blast all the carbon out of the combustion chamber. It may need to be done several times to get it all out.

This was the method back in the days of led, points and carbs in my grandfathers ESSO station.

I've actually did the same procedure back in the day. I was taught the method with ATF, but too much smoke! I felt the later adapted water method worked better but was a very a short term fix.

Working for an AMC dealer, there was actually a warranty code for removing cyl head and decarbonizing pistons and combustion chambers. That too was a short term fix. Some of the seasoned techs I worked with talked some engine seemed to be amune from it and it could be combustion chamber design related. The idle stepper sol. seemed to work best in my opinion, then unleaded gas came along and the problem went away just like the wind.

Just a thought, perhaps the engine fumes disposal recirculating to the flame arrestor could be inducing some carbon build up. Seems like it would take an awful lot though.:huh:.

...Ron
 
Last edited:
Ive got the running on problem too and i have thought about approaching a carburettor specialist to install an ignition switched solenoid in the idle passage to close it off when the key is turned off as they do in cars.I know it will be a tricky operation but i think it may solve a big problem we are all having!
 
Hi Guys

Spent this week end on the water, after trying the water sprayed into the carb trick. I also tried a carb cleaner, the aerosol type you spray into the carb.

Sadly the problem is now worse. The idle is now arround 1500 - 2000 rpm. Turning the idle screw ( what I believe to be the idle setting) completley out does nothing. Screwing it in increases the idle rpm. To stop the motor running on I now have a water bottle with a flip top lid which I spray into the carb, otherwise it does not stop. Nope not at all, it will run on untill it runns out of fuel. If I close the choke it backfires, not pretty!!

Retarding the timing only looses power but does not stop the run on.

My local mechanic is also at a loss, he suggested replacing the motor with a V6 wich I am keen on except for the $$.

Any pearls of wisdom?

Thanks
 

Forum statistics

Threads
112,948
Messages
1,422,804
Members
60,930
Latest member
Ebrown69
Back
Top