Mercruiser 470 wiring system - extra red wire?

[Blueghost924]

I'm still working out electrical problems with my 1982 Mercruiser 470 electrical system. I'm looking at my 9 pin wiring harness that goes from the engine connection to the 8 pin rectangular plug inside the center console. Aside from the 10 gauge red wire, there appears to be a 14 gauge red wire in the harness. I'm not sure why it's there, but it does appear to be cut. Any ideas why this smaller 14 gauge red wire would be here? I did a physical count, and all 8 wires that should be there are physically there, and match the electrical diagram for the Mercruiser 470 (batter circuit).

Offhand, with the 9 pin (8 wire) connector plugged in and the battery connected, is there a way to see if the ignition switch is getting juice? I know the wires 5, 6 and 7 are involved with starting and running. I'm currently using jumper wires directly at the engine wiring at pins 5,6 and 7 to an ignition switch to get the engine started, but I need to get the wiring system correct as to be able to start at the center console.

Thanks!

 

[stonyloam]

sounds like the PO may have added a wire. I think from the diagram you should have 12V at female #6 connection in the plug. Check for voltage there, and at the back of the switch if you can get to it.

 

[Blueghost924]

Thanks Terry. I bought a used gauge board with instrument wiring from a local boat store for $35 as a spare/testor. I ran jumper wires straight from the engine female plug to the rectangular 8 pin spare gauge board I bought, and the engine started right up (essentially bypassing the 18 feet of main wiring harness). I do believe I have a bad main wire harness (from the engine to the center console). Looks like they run used around $80 - but do I really want to get used?? I thought about the prospect of making a harness myself (using the existing plugs) but that may cost almost as much.

 

[stonyloam]

A bad wiring harness usually means corrosion at one end or the other. The wires themselves should be OK unless you can see some physical damage. See if you can check the back side of the connector for broken or corroded wires.

 

[Blueghost924]

I did find the red wire looked bad about a foot from the black round plug and been spliced a long time ago. I cut the red, yellow and purple wire back 6 inches from there (a total of about a foot and a half from the black round plug). I jumpered these 3 wires straight to the engine female connection, and she turns over and starts from the center console. Must be that wiring near the plug. Now I'm wondering how the best way is to repair the section of wiring. I'm thinking about replacing that entire foot and half with new wiring up to the black plug.

 

[stonyloam]

Ok so as I understand you have the male plug with about 18 inches of R,y and p wires. Try taking your ohmmeter on the male end in the plug to the end of the wire and check continuity. That should tell you which one(s) is bad. If you can do that then if you can get to the back of the plug you should be able to just replace the bad wire. If you can't, just splice the good wires back together (solder, or a crimp connector) and splice in a wire to replace the bad one and put a male connector on the end, cut the corresponding wire from the female side of the connector and put on a female connector, then just plug everything back together. Get some liquid tape and coat all of the splices and the new connector to waterproof them once you get all together. You should be able to cut through the cured liquid tape should you need to unplug the new connector. Hope this makes sense.

 

[Blueghost924]

I explored the other downstream wires, such as the tan, blue and black ground wires. Unfortunately, they are not working, so I'm going to play it safe and buy a new wire harness. My boat is a 1986 model, and I'm pretty sure the existing is the original. It may be time...

 

[Blueghost924]

On a side note, I measured the distance from the back corner of my boat up the side to the point that's parallel with my center console, and it measured 10 feet 9 inches. To allow for enough wiring, I'm thinking a 17 foot long wiring harness should fit decently.

 

[mr 88]

You can always use a piece of rope to measure the length needed instead of guessing and having few extra feet of wiring to deal with.

 

[Clv1984]

So i have a question too. I have two wires that are down by my starter on my 1989 mercruiser 3.7l. Onw is white with blue tracer and is a hot wire. The other is black and is for sure a ground. Both have terminals on them but i can't find where they go. I cant a diagram with this white and blue wire on it. Any help would be awesome. Thanks.

 

[GA_Boater]

So i have a question too. I have two wires that are down by my starter on my 1989 mercruiser 3.7l. Onw is white with blue tracer and is a hot wire. The other is black and is for sure a ground. Both have terminals on them but i can't find where they go. I cant a diagram with this white and blue wire on it. Any help would be awesome. Thanks.

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