Mercruiser Alpha 1, 3lt 2003' wont stop?

cake7

Cadet
Joined
Jun 29, 2005
Messages
9
Can anyone help, I have a bayliner with inboard 3ltr Merc Cruiser 135hp aged 2003. when its warmed up, if I turn the key or flick the kill switch to stop the engine, it will continue to run (be it spluttering and coughing)for at least 5 to 10 seconds. what would cause this to happen??? please help.
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

The major reason for dieseling is idle rpm too high, and shutting down immediatly after a hard run. Allow to idle for a couple of minutes before shutting off.<br />The idle rpm also needs to be below 700rpm.<br /><br />Could also need a tuneup, timing reset, mixture changed (richer).
 

cake7

Cadet
Joined
Jun 29, 2005
Messages
9
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

Many thanks, I'll get it check out, cheers
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

Low octane fuel will cause the same problem. What are you running, 89, 92?<br /><br />Chris..........
 

cake7

Cadet
Joined
Jun 29, 2005
Messages
9
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

I mainly run it on 98oct but sometimes will part fill it with 91, many be I should run it solely on 98 or 91, both are recommended by the place I bought the boat from?
 

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

First things first, the most likely culprit is carbon build up in the combustion chamber. after running hard this carbon is hot enough to ignite the air/fuel mixture with out the spark plug, and will continue to do so until it cools down. You can do this yourself, allow the engine to idle abit before shutting down. you can also change the heat range of your plugs, retard the timing, use higher octane gas, etc. However, the cause will not have been addressed. You need to remove the carbon build up, try seafoam or one of BG's intake cleaning products. Cheap and simple.
 

chrisg

Chief Petty Officer
Joined
Jun 29, 2004
Messages
476
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

I have learned that this is a common issue with the Merc. ( there is another thread that someone listed the service bulletion form Mercury about this issue). You have to let it idle for a few minutes befor turning it off. Also putting the blower on helps. If you turn the idle below 600, you will get problems starting when cold.<br /><br />It something to live with. <br /><br />I made the mistake of having a marina adjust my 3.0L and I just got it back working right. ( and it runs on- but I will live with it - Atleast it has power again!)<br /><br />you boat is not old enough to have issues with it! Leave it be. Also, The energency switch should only be used for that- emergencys- not for regular engine shutoff!<br /><br />So take my advice - lessons learned the hard way, If it is running fine, DON'T touch the engine! Try the Higher octane stuff if you want.<br /><br />There are many threads on this issue, you can read them to see what others have done.<br /><br />Take care!
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

Not very good advise you are giving here CI. But I guess every one has different opinions.<br /><br />
it runs on- but I will live with it
The dieseling (run on) usually has the engine running backwards and can cause water to get sucked back into the engine. This can cause hydrolock, and if you are in salt water and it does this at the end of the day and sits in there for a week or two till you use the boat again, can cost you an engine. Even in fresh water, water in the engine is not a good thing.<br /><br />
So take my advice - lessons learned the hard way, If it is running fine, DON'T touch the engine!
Doing preventive maintenance and fixing minor problems is what keeps boats running for a long time.
 

Limited-Time

Vice Admiral
Joined
Mar 30, 2005
Messages
5,820
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

Don S, <br /><br />You posted a "Fairy Tale of a Merc Service Tech." (Or some thing like that) awhile back. It was a story about factory set 3.0 liter Mercs running lean, causing detonation and run on. Our heroes quest was to correct the factory fuel settings, so the 3.0 and their owners could live happily ever after. It may well need re-posting. Nice story BTW.
 

chrisg

Chief Petty Officer
Joined
Jun 29, 2004
Messages
476
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

Don:<br /><br />I asked the same question regarding Run-on, and got this same advice. But I called the merc dealers, and each one told me there is nothing to be done about it - its a fact of the engine. I even called Mercury themselfs, and got the same responce (And it did not hurt the engine). When I found a marina to adjust my engine, I lost all power and it was messed up.<br /><br />All I'm saying, is that Kai's boat is not that old for needing timing or carb changes. I'm not talking about perventive maintenance, just not to try and fix something that an't broke!<br /><br />I would be interested in reading this posting discribed by LT.
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

Ahhhhh Yes, the Fairy Tale, not to be confused with anything real life however.<br /><br />
Let me tell you a fairy tale of a 2004, 3.0L Mercruiser engine that destroyed itself.<br />Once upon a time there was this Marine Mechanic, that shall remain nameless, that had to replace a 3.0L Mercruiser engine under warranty due to a broken valve that destroyed a cylinder wall and piston. After replacing the long block with a brand new one, the engine was very hard to start, hard to keep running till it warmed up and dieseled severely when shut off, even after idling for several minutes and not over 140° temperature, and there was absolutly no carbon buildup since it was a brand new engine.<br />The timing was spot on, and since this engine had the EST distributor was set at the proper timing per the manual and done while in the base timing mode. Still the same problems. It was obvious the engine was running too lean but with the anti tamper devise on the carb mixture screw, it was impossible to adjust it richer.<br />Knowing the lean mixture was probably the cause of the engine failure, the MM (Marine Mechanic) decided, against his better judgment, that the problem with the engine would occur again in a very short time if not prevented somehow.<br />Knowing full well that the California EPA may rain fire and damnation on him for the rest of natural born life and on into the unknown after death, the MM decided to take the matters into his own hands and remove the tamper proof cover over the idle mixture screw. He soon found this to be a very difficult task, but somehow managed to remove it without destroying the carb or the screw. (He later found it would have been much easier to order a new mixture screw and just replace it and go ahead and break the old one off.) <br />Finally after the success of removing the dreaded seal, he backed the mixture screw out approximately a quarter to a half turn. the engine then smoothed out and ran great, idled smooth and slower without dieing and was even easy to start for the first time in it's life, even cold, and never dieseled again when shut off. <br />While the MM is worried about the hereafter and the consequences of his irresponsible act against the California EPA and all the other mini EPA's of the world, along with the consequences of his complete disregard for the Mercruiser procedures outlined in his service manual, the dastardly dead was done...............<br />The customer, however, wondered why his boat now worked perfectly but the poor ole MM was unable to tell him the truth and worries to this day he will be found out and that upon passing he will be sent to the worst part of purgatory for his serious misdoings, but I will......uh, sorry about that, he will be happy in knowing that the boats engine will now live and last for many trips to the great fishing grounds of the owner.<br /><br />Please understand that this is only a fairy tale and should only be told in the proper company, and hopefully someone will not irresponsibly put this in the Vault or something silly like that as it should NEVER be mentioned again as someone else may try it and also be condemned to eternal damnation of the EPA gods.<br />
 

Limited-Time

Vice Admiral
Joined
Mar 30, 2005
Messages
5,820
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

Quote: Please understand that this is only a fairy tale and should only be told in the proper company, and hopefully someone will not irresponsibly put this in the Vault or something silly like that as it should NEVER be mentioned again as someone else may try it and also be condemned to eternal damnation of the EPA gods.<br /> <br />Don, if that were to happen at least you.....er a......I mean.....our hero would be in good company throughout their dam nation.
 

chrisg

Chief Petty Officer
Joined
Jun 29, 2004
Messages
476
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

Ha! So thats my problem! My frend, when he looked at my plugs said it looks like the thing is running lean!<br /><br /><br />Sounds like Lean is OK for meat, but not for engines!<br /><br />Guess what I'll be playing with once I get my manual! :D
 

cake7

Cadet
Joined
Jun 29, 2005
Messages
9
Re: Mercruiser Alpha 1, 3lt 2003' wont stop?

Hey thanks for all and I mean ALL the advice, I to will be looking at a screwdriver and a half turn (after reading said manual) and see what happens too! thanks again.
 
Top