Mercruiser 4.3L MPI 2004 - Stalling and alarms

fwpoole

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Jul 8, 2013
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Hi, hoping someone can be of assistance. I live in a remote area...no mechanics. I hooked my 280 sundancer up to the garden hose and ran each engine for 10-15 minutes everything was fine.

On launch day, after a couple of minutes the port engine stalled with the alarm (beep) going off evert 2-3 minutes or so.

Spoke with a mechanic by phone he asked if the engine started at WOT. After checking the fuel/water separator, tried starting with WOT. The engine started no problem but would die once I brought the throttle back below 800 rpm. Alarm still sounding every 2-3 minutes.

This morning, put some injector cleaner in the gas and took the boat out for a ride...hoping the problem would go away..

After approx 10 minutes into the ride at cruising speed (approx 3000 rpm) the alarm became solid with a message reading (Reduce Throttle)

I shut the motor down.

Tried starting again once back at dock, start with WOT but stalls once the throttle is pulled back in the normal position.

No diagnostic tools or scanners around.

Can anyone help?

Fred
 

alldodge

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Re: Mercruiser 4.3L MPI 2004 - Stalling and alarms

No expert on smart craft but upon reading the manual it says you should be able to scroll through the messages after seeing reduce throttle. Did you use the + and - buttons and if so what was it telling you?
 

Fun Times

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Re: Mercruiser 4.3L MPI 2004 - Stalling and alarms

Since you are able to start it with the throttle opened up a bit, that is usually an indication that the IAC idle air control valve is amiss and/or the IAC muffler is dirty.

Either or has been known to sound the warning horn at all RPM's and is somewhat a common failure.

Without a scanner tool, most MPI diagnostics become a guessing game of what could be wrong until you come across an item amiss by testing each item independently with an service manual, ohm meter fuel pressure tester gauge, etc, etc in hand.

Bear in mind that i'm not saying this is your engine running problem as it could be a number of things, but based on your description it has the most resemblance of being an IAC problem.

Item #6 is the IAC muffle and item #16 is the IAC Valve,
http://www.mercruiserparts.com/Show...71.png&inbr=11705&bnbr=80&bdesc=Throttle+Body

Hope this helps, Good luck with it.:)
 

fwpoole

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Jul 8, 2013
Messages
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Re: Mercruiser 4.3L MPI 2004 - Stalling and alarms

No expert on smart craft but upon reading the manual it says you should be able to scroll through the messages after seeing reduce throttle. Did you use the + and - buttons and if so what was it telling you?

Thanks, I didn't...but will try, maybe it is still there. Will let you know if I find anything..
 

fwpoole

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Joined
Jul 8, 2013
Messages
7
Re: Mercruiser 4.3L MPI 2004 - Stalling and alarms

Since you are able to start it with the throttle opened up a bit, that is usually an indication that the IAC idle air control valve is amiss and/or the IAC muffler is dirty.

Either or has been known to sound the warning horn at all RPM's and is somewhat a common failure.

Without a scanner tool, most MPI diagnostics become a guessing game of what could be wrong until you come across an item amiss by testing each item independently with an service manual, ohm meter fuel pressure tester gauge, etc, etc in hand.

Bear in mind that i'm not saying this is your engine running problem as it could be a number of things, but based on your description it has the most resemblance of being an IAC problem.

Item #6 is the IAC muffle and item #16 is the IAC Valve,
http://www.mercruiserparts.com/Show...71.png&inbr=11705&bnbr=80&bdesc=Throttle+Body

Hope this helps, Good luck with it.:)

Thank you, I will check it..
 

fwpoole

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Jul 8, 2013
Messages
7
Re: Mercruiser 4.3L MPI 2004 - Stalling and alarms

You are right...thank you!! I took the IAC valve off the starboard engine and installed it on the port engine. She started right away...no alarms..no stalling!

Thanks again, probably a good idea for me to invest in an inexpensive scanner...
 

Fun Times

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Re: Mercruiser 4.3L MPI 2004 - Stalling and alarms

You are right...thank you!! I took the IAC valve off the starboard engine and installed it on the port engine. She started right away...no alarms..no stalling!

Thanks again, probably a good idea for me to invest in an inexpensive scanner...
Nice, Thanks for the update.

While you're at it, Make sure you order and install two new IAC mufflers and clean up the throttle bodies as an preventive maintenance.
 

sessasells

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Jun 30, 2013
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Re: Mercruiser 4.3L MPI 2004 - Stalling and alarms

Thanks for the tips. The problem is not cured with the IAC muffler out but the IAC motor looks like the one I had on a ford product and it would get built up from carbon deposits which could be cleaned out rather than replacing the motor for a quick fix. Does this sound like the same situation? If so, does the alarm clear itself or does a mechanic with diagnostic tool need to clear the code (and alarm)? Thanks,
 
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