2004 mercury 75 hp charging system meltdown

Hookm49

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Joined
May 29, 2013
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Hi. I'm new to this Forum but I have a problem that I'm hoping you all can help me with.

I have a 2002 Tracker Pro V-17 boat with a 2004 Mercury 75 HP (3 cyl) and up until this year have never had any issues with the outboard. Before a recent fishing trip (last week) I replaced both boat batteries since they were at least 7 years old. I bought deep cycle 12V batteries from Walmart and checked both of them prior to going on the trip for proper voltage and fluid levels which checked OK on both batteries. I thought I was good to go.

Everything worked fine until 3 days into the trip. I then noticed the Tachometer was not working. I also noticed that the onboard battery minder I had installed several years ago would not show the state of charge of the 2 onboard batteries nor did the #1 Battery (starting) show as being charged by the outboard while running like it normally did. This was normally done by pushing a button for each battery and the level of charge showed up as 25 - 50 - 75% etc. The "charging" light normally was on all the time for battery #1 when the outboard was running.

The morning of the 6th day I attempted to start the outboard but it would not turn over. The starter made sounds as if trying to turn over but nothing else happened. I then switched the outboard power loeads to Battery #2 (trolling motor battery) and the engine started with no problems. We used the boat in that conditon until mid-day when we trailered it to leave. Thinking I may have blown a fuse I removed the engine cowling and found a real mess on the charging system side. The 3 coils appeared to have brown liquid coming out of them and the solenoid and voltage regulator were charred and deformed with the connected wiring harness burned with at least 1 wire burned in half. It appeared the entire system had overheated to the point of meltdown.

I checked the battery connection and they were attached to the correct polarity. The batteries both had correct fluid level when I pulled them out of the boat today. Battery #1 checked at 10.89V and is currently on charge.

I cannot find a root cause for the failure. The outboard has functioned flawlessly from the date of purchase until now. I've heard that having a deep cycle battery for a starting battery should NOT cause any issues but I'm not an outboard mechanic. I want to do the repairs myself since I have all the appropriate tools but hate to begin until I know what could have caused such a catastrophic problem.

Has anyone encountered a similar problem as this or have any recommendations on what I should do to figure out what happened? I'd hate to replace parts only to have the same thing happen again.

Thanks for any help you could supply.
 

Hookm49

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Joined
May 29, 2013
Messages
2
Re: 2004 mercury 75 hp charging system meltdown

One further observation based on the thread that you referenced is that the Voltage Regulator actually has a hole melted through it and I believe this is where the "brown fluid" that dripped on the CDM's came from.......and yes I did have a "deep cycle" battery I was using for starting since I read an article saying it didn't matter whether you had a regular starting or a deep cycle battery for that purpose. Evidently it does matter a lot.

Thanks for your reply. Very informative. Now to determine what components are actually needing replaced....and getting a new "regular" starting battery.DSC07136.jpgDSC07134.jpgDSC07130.jpgDSC07129.jpg
 
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