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mystery stalling on a 350 mag horizon

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arcane808

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Hello everyone, hoping I can get some advice on a direction to take on my problem, any advice given is greatly appreciated. The motor is a 350 mpi horizon mercruiser with a bravo1 leg. It is an 2006, has 450 hours on it, and has been well taken care of. The basic problem is that the motor will sometimes (not consistently) die out when coming out of gear being put into neutral. When I first bought this boat the problem didn't occur too often and it was never hard to restart the motor. It would crank right up again no problem. Eventually the problems frequency has increased and restarting the motor has become more difficult. Sometimes after it dies when I try to restart it the starter sounds like its having a hard time. It will crank..1second...crank...1second...crank...1second ....crank...1second. If I stop and give it a few minutes it will turn over again at the right speed. I did some reading and decided to check out the shift switch. I removed it from the shifter (while in neutral) and pressed it over and over again... holding it trying to see if I could stall the motor completely with no sucsess. I also read a bit about this potentially being a shift cable problem. I figured its time to take it to a real mechanic. The local merc dealer told me they don't think it has anything to do with shift cable ( apparantly they told me thats only a problem with alpha legs) and proceed to hook it up to a computer to check for error codes. It did show one abnormalty. The computer couldn't recognize when my boat was in gear or out of it, it would just stay at neutral regardless of gear. They reset it and told me that was most likely it. I went home took the boat out and the problem is still there. They also gave my IAC a clean bill of health. I have been unable to show them the motor stalling in their shop because its also a problem that doesn't usually happen until i've been running the boat for at least a few hours. I'm pretty much out of ideas on what to check next. If anyone has any idea please let me know. -Thanx
 
It will crank..1second...crank...1second...crank...1second ....crank...1second.

Are You trying to say that the starter is cranking the engine like the battery is dead? If yes, when this happens you need to carefully feel all the battery and ground connections and look for the one that is getting hot. This includes the short strap connection between the starter solenoid and the starter motor on the starter. If all is cool. You need to check the amperage draw of the starter.
 
Normally that switch will not kill the engine.
The switches job is to tell the PCM if it's in gear or not. Since you played with the switch, that would/could be a reason why your PCM could not recognize what gear it was in.

arcane808 said:
I did some reading and decided to check out the shift switch. I removed it from the shifter (while in neutral) and pressed it over and over again... holding it trying to see if I could stall the motor completely with no sucsess.

It did show one abnormalty. The computer couldn't recognize when my boat was in gear or out of it, it would just stay at neutral regardless of gear.

They reset it and told me that was most likely it.

I went home took the boat out and the problem is still there. They also gave my IAC a clean bill of health. I have been unable to show them the motor stalling in their shop because its also a problem that doesn't usually happen until i've been running the boat for at least a few hours. I'm pretty much out of ideas on what to check next. If anyone has any idea please let me know. -Thanx
Click to expand...
What did they reset? The switch back to installation specifications or did they just clear the faults in the PCM or both?

Agreed with dockside, Look for hot, loose or corroded wire connectors/connections.

Also don't rule out the IAC, It's an electric motor and they do get hot enough to completely meltdown at times. Carefully keep an eye on the IAC's temperature as well.
 
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Yes, as if the battery is dead is exactly what I mean. I will check all those connections in the next few days. Would one of those wires also be a plausible explaination for the motor stalling out when comming out of gear into neutral? And since the problem is not consistent would heat in the wires likely be present only when stalling/slow cranking occurs?
 
I didn't realize the shift assist switch also let the PCM know what gear it was in besides partially stalling the motor. You could be very right that may be the reason for the code. The mechanics reset the PCM faults only and told me it was working again. I reinstalled the switch the day before I brought it in to them. I have a seloc manual for the engine and tried to install it with the exact directions they gave(but I guess I could have screwed it up too). I will check the IAC's motor out. And I just wasnt to thank you both for your replies, This is the third forum Ive posted on and the only one that even gave me a reply.

Mahalo nui loa -chris
 
Hey guys, here is the update. Iv'e been able to check the IAC motor. At running temp (168f) it is warm, but not at all hot. Ive checked all the wiring comming off the battery ( anything within reach really) and found nothing warm. I could not get to the starter, it is totally inacsesable. I can't reach it to check the short strap to the solenoid. So that will have to wait till I find a guy with arms at least six inches longer than mine. I may actually have to remove a few large engine parts to get to it. I also didn't find anything loose and even took the time to sand down all the terminals connected to the battery. I will recheck all those wiring connections for hot ones the next time I take the boat out ( after it stalls of course). Anyway, I will figure out how to get to the that last cable eventually, but in the meantime does anyone have anyone have any other suggestions to try? As always I greatly appreciate the any help received. -chris
 
Sorry it took so long to reply, been busy working. I finally tested the battery with a meter and when cranking the voltage starts at 12.4 then drops to 8.5. Within a second its back up to 12.4 then climbs quickly to 14.4 with the motor running.
 
Ok, replacing the battery will get done. Is a bad battery a plausible explanation for the motor stalling when coming out of gear? Or do I likely have two different problems ( bad battery and something else )?
 
Battery going down that low at start up is a problem, however, I wouldn't be so quick to change them. As Dockside mentioned earlier, check all your connections first as bad ones will also cause voltage drops, and the computer doesn't like that. When you're convinced the connections are OK, then replace the battery. Get 1000 MCA or 800 CCA start battery. The stalling when coming out of gear could be unrelated, perhaps a cable adjustment, bad cable, interupt switch (Alpha by an earlier post).
 
Could he be confusing it with the neutral safety switch? He stated that he removed it from the "shifter" and couldn`t get it to stall the motor.
 
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