I hope someone can help connect a few dots on this project. I have an old boat with an old 1976 Mercury 1500 on it. Recently I began redoing the wiring as the previous owners made a mess of it -- wires going to no where, cracked casings, etc. After examining the wiring harness I decided to order a new one (Sierra 18-5511). The new harness does not have all the wires that the old one did. I suspect that one of the previous owners spliced into the original 45987 Merc harness and added in some extra wires so they could hook up various accessories. On top of that, the control box itself is much newer than the original but again, I'm not entirely sure if it is factory or if someone might have modified that as well. What I'm hoping someone can help me with is:
1. A bit of insight into how it might be wired
2. If there is a better way to wire in the accessories than splicing the harness
3. If there are adapters to make this easier to wire (I know there are some adapters for connecting newer equipment to older harnesses but I'm not entirely sure if they apply in this situation or not)
4. A bit of sanity (I know that is asking a lot)
The control box I have is RC881170A13:
And here are a few images of the old wiring harness. You can see how bad of shape they were in along with what I believe to be the spliced in wires (would love it if someone could confirm that for me):
The accessories are your typical gauges (fuel, speedo, tach, etc) along with a switch box for lights, pumps, instruments. I believe the original idea was that they switch box only worked if the key was in the on position though I'm not entirely sure if that was wired right. I seem to recall that I could turn the bilge pump on with the key off. My plan is to get the whole thing wired sanely. Before I had about 15 different ends that connected to the positive terminal on the battery and about 4 for the negative. I'd like to get that down to a single one. I'd also love to get this all wired into some sort of box where I could label what is what rather than having a spider web that runs all over the place but that is secondary to actually figuring out the right way to wire in the harness and control box.
Thanks for any help / insight. I can provide more information and pictures if there should be any questions!
1. A bit of insight into how it might be wired
2. If there is a better way to wire in the accessories than splicing the harness
3. If there are adapters to make this easier to wire (I know there are some adapters for connecting newer equipment to older harnesses but I'm not entirely sure if they apply in this situation or not)
4. A bit of sanity (I know that is asking a lot)
The control box I have is RC881170A13:
And here are a few images of the old wiring harness. You can see how bad of shape they were in along with what I believe to be the spliced in wires (would love it if someone could confirm that for me):
The accessories are your typical gauges (fuel, speedo, tach, etc) along with a switch box for lights, pumps, instruments. I believe the original idea was that they switch box only worked if the key was in the on position though I'm not entirely sure if that was wired right. I seem to recall that I could turn the bilge pump on with the key off. My plan is to get the whole thing wired sanely. Before I had about 15 different ends that connected to the positive terminal on the battery and about 4 for the negative. I'd like to get that down to a single one. I'd also love to get this all wired into some sort of box where I could label what is what rather than having a spider web that runs all over the place but that is secondary to actually figuring out the right way to wire in the harness and control box.
Thanks for any help / insight. I can provide more information and pictures if there should be any questions!
