Fried ground wire

[shadowrider]

I have a mercruiser 3.0, turned the perko switch to all to tilt drive when this ground wire went up in smoke. Immediately shut off perko switch, when smoke cleared all I found fried was this wire that goes from bell housing to transom drive plate.
My question is what caused this possibly and should I replace with same type or go heavier ? Thanks

 

[Don S]

Re: Fried ground wire

You have something wired to the battery or battery switch wrong.

 

[mark1905]

Re: Fried ground wire

You have something wired to the battery or battery switch wrong.

What Don said. You have a direct short due to something being connected wrong. You basically just connected your positive and negative battery terminals together via that wire, and it became an arc welder. Replace that cable with the same gauge and figure out what you have connected incorrectly or you'll do the same thing all over again..

 

[shadowrider]

Re: Fried ground wire

I used the boat all summer last year, I have done nothing to it since, I have not wired anything. Sure sounds like something is wired wrong.

 

[mark1905]

Re: Fried ground wire

It sure sounds like a direct short and not just corrosion buildup causing a jump. For wires to full on fry like that, something is touching something pretty solidly that it shouldn't be..

Trace things back.

 

[shadowrider]

Re: Fried ground wire

I take that back, I had to remove a speaker from the armrest to get armrest reupholstered. I put it back in but wired it correctly. I did not turn on the stereo however, so I would not think that's it. Will have to recheck it.

 

[pyrotek]

Re: Fried ground wire

You basically just connected your positive and negative battery terminals together via that wire, and it became an arc welder.

I would say it acted more like a fuse Replacing the wire with a thicker wire is like increasing the fuse size without fixing the problem. You'll probably just create more smoke!

 

[Don S]

Re: Fried ground wire

Did you try to operate the trim after you turned the switch on, or did the wire just smoke with the switch turned on.

That wire is nothing more than a bonding wire, and shouldn't have any power to it at all. It just bonds the transom shield and drive to the engine, which is hooked to the negative side of the battery.

Did you have the battery removed or disconnected over the winter?

 

[Bt Doctur]

Re: Fried ground wire

you need to be very specific ,EXACTLY where is the negative cable attached?

 

[shadowrider]

Re: Fried ground wire

I did not disconnect the battery, Negative cable goes to bell housing on back of motor opposite the fried wire. after the wire fri incident, and the smoke cleared I turned the switch back on and trimmed up the drive. I think the wire fried when I began trimming the motor. I used the "trailering " switch, which I dont normally use. Is the trailering switch the same as trim on throttle lever?

 

[RenkenII]

Re: Fried ground wire

I would say you have a bad relay for that switch. When you activated it, the relay failed sending the juice the wrong way. Swap the wire and all the relays in your unit - cause if one goes, the others will fail soon.

 

[Bt Doctur]

Re: Fried ground wire

the trim pump has a #10 positive and negative power lead that usually go directly to the battery..neg goes to the mounting frame and thats where the solenoids get their ground.the bonding wires do not carry battery power and to melt them means some serious current was passed thru them.

 

[shadowrider]

Re: Fried ground wire

I did some short hunting on the boat. I turned on the perko to "all" again and began trying everthing. Everthing seems to work, (except the horn). I had to raise the bimini to free up some space to work. Anchor light on top of bimini I noticed was full of water. The boat has a canvas storage cover propped up by poles inside boat to keep rain out. It is not perfectly water tight. I checked continuity to the socket and it is dead. I know it worked last summer.
I do have power to the quick connect at the base of the bimini. Could this be my problem? I would think not. Is it possible the perko could have had water in it ? Trim pump functions normally.

 

[BaileysBoat]

Re: Fried ground wire

the trim pump has a #10 positive and negative power lead that usually go directly to the battery..neg goes to the mounting frame and thats where the solenoids get their ground.the bonding wires do not carry battery power and to melt them means some serious current was passed thru them.

Right on. The main ground failed.

 

[shadowrider]

Re: Fried ground wire

I went out and checked connections on those #10 wires. The negative is on the wingnut battery terminal, I tightened it up getting about 3/8 to 1/2 turn on it, which seemed a bit loose. I tightened with a cresent held vertical. Other end of negative cable tightened up very little. Main negative battery cable on block got maybe a 1/4 to 3/8 turn. I am feeling confident you guys are steering me in the right direction. Thanks. Keep the comments/ideas etc. coming.

 

[stonyloam]

Re: Fried ground wire

OK time to look at the facts: The only way that could have happened is if all of the current from the trim pump traveled through that wire. That wire only goes from the transom plate to the flywheel housing and is engine ground on both ends. Is there another black wire on that wingnut terminal, and is there a heavy black ground wire on a separate battery post?

 

[wellcraft-classic210]

Re: Fried ground wire

One thought; Have you tried doing some measurement with a DVM? You may be able to place it in the same path where the wire melted & check for voltage as different things are cycled. This is assuming the ground wire that melted is still open or removed.

The only way that wire would have melted is for something to apply a voltage and the wire that melted was in the path to of from ground.

 

[stonyloam]

Re: Fried ground wire

The only way that wire would have melted is for something to apply a voltage and the wire that melted was in the path to of from ground.

The problem is both ends of the wire that melted are supposed to be engine ground. That makes it a little confusing as to how it happened.

 

[stonyloam]

Re: Fried ground wire

Hay! Is that an aluminum boat? Maybe the hull became energized (direct short from battery +) and the current flowed back from the transom plate to the engine ground. It kind of looks like the wire got hottest at the engine end (little bit of insulation left on transom end).

 

[shadowrider]

Re: Fried ground wire

The boat is all aluminum, and that sounds reasonable. I really cant remember if the wire started frying as soon as I turned on the switch or when I hit the trim switch. ( i think it was the latter.) The wingnut terminal has several other wires on it. The heavy ground is next to the wingnut terminal, on a seperate post.
The burnt wire is still in place, have not tried a DVm measurment, I dont have one, or an assistant available. May have to obtain both to get to the bottom of this.