Mercury voltage regulator problem

[beck1940]

I have a 2011 Mercury Outboard 60 hp 4 stroke engine. I was running it on the water going about 25 mph when everything shut down leaving me stranded in the middle of the lake. I had no power to the ignition, live wells, or anything. I carefully removed the cowling and checked the main fuses to the motor. The 15 amp fuse was blown. I replaced it, and then started the motor back up. I then ran idle speed back to the boat ramp. Four years ago, I had the same thing happened. I took it to the Tracker dealership for repair while it was still under warranty. They said the voltage regulator was bad, and they replaced it. If this is happening again, I wonder why they go bad. I have a 2 year old starting battery that I keep fully charged when not in use with a Minn Kota onboard charger. Any advice is greatly appreciated.

 

[ajgraz]

Carefully check all under cowl wiring for chafing or fraying, you could be getting a direct short.

 

[alldodge]

Not an OB guy but just looked up 4 stroke Merc and like stern drives, the main fuse for the motor is a 20 amp fuse. The 15 amp was listed as smartcraft, and the 3 others are 20 amp

http://boatinfo.no/lib/mercury/manuals/40-50-60_02.html#/24

 

[sam am I]

It's electrically impossible (those mech's took your money) for that reg/rec (shorted, not regulating, whatever) to blow main fuse (#2)! They might as well have said the battery was also responsible for blowing the main fuse #2 and sold you a new one of those too........geeesh.

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With the extreme exception of this/a paralleled 12V battery with its reg/rec both well up beyond 20+ volts (along with all your lights, electronics etc systems all smoking), the problem (shorting to ground) exists down stream (red/purple and beyond side) from the fuse......... Agree with Ajgraz, look for something AFTER the main fuse (red/purple path) shorting to ground if the 20A fuse blows the Dodge found that should be being used.

 

[lmuss53]

These are notoriously fickle charging and regulating systems. I won't pretend to understand what Sam is explaining above, but I have seen these blow the main fuse and or smoke the regulator/rectifier and fry the wiring harness all because of a loose wing nut on a battery.

On Mercury motors it is always a good idea to use a marine specific battery, take every wingnut off the batteries or other connections and replace them with nylock nuts, and clean and double check every connection every year.

That rectifier/regulator is on a LOT of Mercury motors for a lot of years. The fuse in the red wire is a recent addition, before it was added there were lots of melted down wiring harnesses around. I have brand new rectifiers on the shelf with no fuse, I have started adding a 30 amp fuse in that line when I replace these regulator/rectifiers. If the fuse blows check all your connections for a loose one.

 

[sam am I]

but I have seen these blow the main fuse and or smoke the regulator/rectifier and fry the wiring harness all because of a loose wing nut on a battery.

I would agree in that that was the specific situation I was referring to above......The sudden loss/disconnect of the reg's loads (the battery is paralleled with all other loads) and which you made a good point of due to either flaky battery connections or, better yet, someone shutting off the batt switch while running can cause the reg to over shoot (see load regulation), and esp at high speed where the input to the reg is 20-25V.

If this occurs, there can be a volt spike seen by all the electronics. If any of those electronics have a clamp type circuit on their power inputs AND have no fuse of their own, the current through the main fuse spike accordingly which can blow the main fuse. Normally however, every device has their own fuse, say 1, 5, 10 amps and the device fuse goes before main fuses do.

Smoked wire harness I've seen as well when the reg shorts to ground and the battery now supplies current backwards into the reg to ground, this fries the wires and the main fuse remains perfectly happy due to its not in that current path.......Been there done that!!