Where does AC green ground wire terminate on 7.4l engine?

Loneranger

Loneranger

Well-Known Member
May 2, 2008
1,068
Knoxville TN
Boat Info
2000 SeaRay Sundancer 270
Engines
7.4l Mercruiser w/ Bravo III
I was replacing a bilge pump hose that had a hole in it last week and noticed a green wire with a ring terminator on it loose in the bilge. It is about a 6 gauge wire with green insulation wrapped in black flexible plastic protective sheath. I did not have the time to trace it to its source yet nor did I take any pictures. I will be doing this on tuesday.

The wire comes from the general direction of the starboard gunnel and the loose end I found seems to go to about the middle of the 7.4 l engine on the bottom. From my understanding of current ABYC codes, the ground wire for the ac system is connected to the DC system at the engine block. I think this wire may be that connection. I think it originates at the circuit breaker for the shore power connection but obviously not sure. I am not sure if I knocked it off when replacing the bilge hose or if it has been lying loose for some time.

Any idea of where this wire terminates on the engine? Looks like it will be a PITA to get under there.

John
 
I do not think it is on the DC side. It certainly does not come from the DC breakers which are on the port side. I will trace it to its source tuesday and let you know.
 
John, green bonding wires connect from item to item to spread current flow to slow galvanic corrosion. These wires will not appear to be part of the DC system. You do need to find out where this came from as a small amount of current can eat away quickly without it. A BIII makes it even more important. MM
 
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It could be a DC bonding wire, I forgot about them. Ah marine wiring...

If so I still am not sure where it should attach. I have a long lead for my volt meter and can test all my through hull fittings to see where I am getting a different voltage potential. I have 2 sea cocks (AC and generator), the drive, the generator exhaust (the other above the water through hulls are not metal), and the transducer (although not sure of its composition). May be easier to check each piece than to measure voltages.

Where does the bonding wire attach to the drive (the loose end is closer than to any through hull)?

I will know a lot more Tues when I get a chance to go over it in more detail. I will take some pictures also if I cannot figure it out.

John
 
The wire probably broke off at the connector which means the connector is still screwed to the seacock or whatever. That means that whatever it is supposed to be connected to is within the range of how far you can stretch the wire.

So, stretch the wire in all directions and you will figure out where it goes.
 
I forgot my camera today but I traced the wire. It originates on a buss bar aft of the engine on the starboard side. It is an 8 gauge and has no number tagged to it. The other wires on the buss are all green and tagged 743, 721, 706, and 704. None of thes numbered wires are found in my 270 wiring diagram.

The wire has not broken off its connector. It has a ring connector firmly attached. It can reach the starter on the engine. I see no obvious bolt on spot for this wire. I thought it connected to the through hull for the transducer but it is all non conductive materials and no place for a bonding wire.

Also this wire may be aftermarket as it has red crimped on ring terminals booth ends. The other wires on this buss are all cover in shrink tubing black.

Any ideas? I suspect this wire has not been connected for a long time. I only noticed it since I was replacing a bilge hose that runs under the engine.
 
Doesn't sound like it came from the factory given the crimps you refer to. As MM said, anything added (like a through hull for macerator pump or air conditioning) and forgot to hook it up?

If not factory and nothing in its range of travel, I don't know how you can figure it out.
 
The generator was added with its correspondant throughhull but it did not go there for sure. I had the dealer replace the exhaust shutters otherwise I have done all the preventative work in the bilge and do not specifically recall pulling this wire loose.

Only other idea i have is the entire sterndrive was replaced prior to me buying the boat due to a collision with an underwater object but replacing the sterndrive should not involve any interior wiring.

On the bright side everything works and I do not have excess corrosion so I may be chasing a non issue (although my boat spends most of its life in a lift so I never have any corrosion issues on any boats). I may ask this winter when it is due to have the sterndrive pulled to check alignment and boots etc and ask the Mercruiser mechanic if they have any ideas. I take the sea ray to the cobalt dealer for things I cannot handle so it wont be the sea ray dealer.

This wire was in a bundle that was running to the underside of the engine well forward of the drive coupler. I only noticed it because I had to remove all the wire ties to remove the bilge pump hose.
 
I might email sea ray direct and see if they can find a wiring diagram of that bus bar and tell me what wires are coming from it. I have the wiring diagrams for the boat but I have not found any 700 series wires except for one that goes to the windlass.

John
 
Brunswick boat customer service got back with me very quickly. They could not help much with the wire in question since it is not labeled. I did get a pdf of the function and run of all the wires that are labeled.

704 engine grounding
706 grounding system jumper
721 drain plug grounding
743 fuel fill grounding

I though my unlabeled wire was going to be the engine grounding but the engine is already ground. I needed to rebed my drain plug this winter and thought this might go to the drain plug but it also is connected. I am at a loss.

John
 
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