Major Electrical Problem

Jakester79

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Aug 18, 2005
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All,
I started my bayliner 2452 classic with a Mercuiser 5.0 the other weekend and there was a horrid squealing sound, I shut her down and done some trouble shooting to find my Alternator was seized up. I turned to power switch off and began removing the Alt, in the process of removal, one of the Alt terminals came in contact with the oil dipstick creating a spark. I quickly moved the alt away from all metal components.
After un seizing the Alt, I reinstalled it and turned the power switch on to go for a start and had NO power to my gages, accessories, GPS, fish finder nothing. I checked the fuses below on the pannel and none were blown, looked back in the battery compartment and found two blown 250v fuses there. Replaced them and turned the power switch back on still nothing. There is a circuit breaker on the engine which is supposed to trip if over loaded but it seams not to be tripped. I disconnected the two leads going to said breaker and used an Ohm/volt meter to test it and the circuit is good.
I have disconnected the wiring harness plug from the engine and checked for resistance up to the fuse board and there is no loss there, I removed hot and ground lead from the fuse board and there is no juice.
I have power to the starter hot lead but nothing from the engine out. Is there a fuse, component or something I could be missing.
What in the world could be to problem?
 

Don S

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Re: Major Electrical Problem

Year of engine?????
 

Jakester79

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Re: Major Electrical Problem

bought the engine from a Mercruiser dealer out of Miami Fl Sept 05, so I am guessing it's an 04-05 year model. The model number I have is 4-M12025R S and serial # of 0W046576 I hope this wil help you in answering or giving direction of what I should check for.
 

Don S

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Re: Major Electrical Problem

On the main terminal of the starter is a square hi amp fuse that probably blew when you shorted it out.
With the battery switch on, make sure you have power on the start solenoid (meter or test light) then check the terminal on the fuse and see if you have power. If not, replace the fuse and you will be back in buisness.
Here is what the fuse looks like.

Square%20Merc%20Fuse.png
 

Jakester79

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Re: Major Electrical Problem

Don,
thanks for the info, I looked at that but wasn't sure what it was. Can you send me the like pulled the info from.

Scott
 

Don S

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Re: Major Electrical Problem

That info is in Merc OEM service manual #31.
 

Bondo

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Re: Major Electrical Problem

If not, replace the fuse and you will be back in buisness.

Or Better yet,........
Throw it Away,+ Hook the Battery Wire to the Starter.........
 

Don S

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Re: Major Electrical Problem

Or Better yet,........
Throw it Away,+ Hook the Battery Wire to the Starter.........

Not sure that's a good idea, he seems to be the kind of guy that the fuse was designed for. :rolleyes:
 

Jakester79

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Re: Major Electrical Problem

Don,
thanks for the last stab, LOL. I know better but just didn't do what should have been done.

Also is removing the fuse really a great idea, yes it may have saved me this time but there won't be future work without the batt's being disconnected.
 

Don S

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Re: Major Electrical Problem

I wouldn't use the fuse on my boat.
The way Merc has it wired in, if the fuse goes bad for any reason, and the engine is running, you loose an alternator.
For years these engines have run without that fuse.
The only reason for that fuse (that I can see) is if the trim pump was hooked to it. Merc used to have the trim pump hooked directly to the battery (NO fuse at all) then when they came out with this square one, seems no one knew what to do with it.
In manual #24, it show the main battery cable hooking to it instead of the starter. You just know a starter is going to pull more than that 90Amp fuse can handle.
 

Jakester79

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Aug 18, 2005
Messages
14
Re: Major Electrical Problem

Don,
thanks for the help in figuring out what the problem was, I pulled the fuse and sure enough it was blown. I thought about replacing it but then thinking along the thought's you said above, I decided to leave it out and hook everything back up.
Looking forward to getting her out on the water in the next week.
 
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