Mercruiser 3.0 Electrical problem

[Nestle488]

I have a 2002 Mercruiser 3.0 with an electrical problem. It quit while I was using it and acted like I had a blown 90 amp fuse (no power to anything but the power tilt). I replaced the 90 amp fuse at the starter and nothing happened, it still has no power to anything but the power tilt. I checked for voltage with a voltmeter and have 12V going in and out of the 90 amp fuse as well as both sides of the 50 amp circuit breaker. I don't seem to have any power up at the instrument panel. I am thinking maybe my ignition switch is bad or possibly the wiring harness although I don't know how it would just fail. Any ideas on a good test before I go spend a bunch of dough at the mechanic?

 

[Bt Doctur]

Re: Mercruiser 3.0 Electrical problem

from the 50A breaker it goes to the main engine harness plug, remove the clamp and inspect the connections. from there it goes thru the harness to maybe another harness plug under the dash, that plugs into the dash.Under the dash check for power on 10Ga red or orange wires,You should have 12v on the red wire at the ign switch.Key to "on" should have power to the purple wire at the switch.

 

[Nestle488]

Re: Mercruiser 3.0 Electrical problem

I checked the harness plug at the engine. It looks brand new. Here is a picture:

I have no voltage at any of the terminals in the plug. There are a couple of large gauge red wires from somewhere on the engine that are connected to each other but not the harness plug, and another red wire that goes to the plug that is severed.

As you can see, the red wire that goes to the plug has been cut and this wire as well as the aforementioned wires had electrical tape wrapped around them so this didn't just happen, the boat ran this way for 2 years.

Does this look normal and if so where could my problem be? Any help is appreciated.

 

[alldodge]

Re: Mercruiser 3.0 Electrical problem

You said red w/ blue strip, it should be a red w/ purple stripe. This wire should go to a 20AMP fuse and then go to the ignition switch. See if the fuse is blown

 

[Nestle488]

Re: Mercruiser 3.0 Electrical problem

You said red w/ blue strip, it should be a red w/ purple stripe. This wire should go to a 20AMP fuse and then go to the ignition switch. See if the fuse is blown

I probably is purple, my eyes aren't that great. No fuses are blown, I checked them all. See my previous post, I modified it after I checked the wiring harness plug, I think the problem is back at the engine somewhere (I sort of hope, at least I can get to it easily!)

 

[alldodge]

Re: Mercruiser 3.0 Electrical problem

SOunds like you know how to trace connections and something does look off in your pics, more so becauase this is a 20002 setup. Trace the connections from the starter RED wire throught the RED/PUR through until you find the break

 

[Bt Doctur]

Re: Mercruiser 3.0 Electrical problem

Looks like some water got in the harness and started corroding. The cut red wire (pic 2)needs to be connected to the other 3 (pic 1)with the green corrosion.

 

[Nestle488]

Re: Mercruiser 3.0 Electrical problem

You were correct, after much gnashing of teeth and testing circuits to make sure I wasn't going to blow anything up I connected the two wires together (for testing purposes) and now I have power as normal. Do you have any advice as to how I should join the wires permanently? I cleaned off quite a bit of the corrosion but am leaning towards cutting that 1 inch portion of the line out and joining the wires (10 gauge I think as well as a couple of smaller wires) with a butt splice. I don't think I can get enough heat to properly solder with what I have but am willing to spend money to get the correct tool if someone can point me in the right direction. Thanks for your help.

 

[alldodge]

Re: Mercruiser 3.0 Electrical problem

Soldering is allways in my opinino but crimp will work. If you crimp, apply some silicone greese or liquid elecrtical tape followed by heat shrink tubing.

 

[fishrdan]

Re: Mercruiser 3.0 Electrical problem

That's why they say not to solder connections in a boat, the solder creates a hard section in the wire and it can break, just like it did in your pic. That said, I still solder, but use a couple layers of heatshrink to create a strain relief, better than nothing....

The repair will most likely leave the red wire too short, so I would add in about 1' of new 10ga red wire, loop it in the harness. (open pic)


To complete that repair correctly you're going to need: a big soldering gun , solder, heat shrink, crimp connectors, etc.

I would, heat up the plastic of a crimp connector and remove it, crimp the new 1' of red wire onto the pigtail wire, solder it, brush it with liquid electircal tape, then heatshrink over it. Get a crimp big enough to fit the 3-10ga wires (plastic removed from crimp) and crimp it on, then twist and double over the pigtail 10ga wire and crimp it, solder it, liquid tape, then heatshrink. Yeah, I'm Captain Overkill...

The only other way I could see doing this repair is to crimp ring terminals on each wire separately, bolt them together then heatshrink over the whole mess. That's going to be big and bulky, and possibly a place to chafe the other wires,,, and you might not have enough wire unless you splice in some length.