1987 OMC King Cobra 5.0 Alternator Issue

[JimL111]

Hi All, I'm a newb here. I've had the boat for about year now, and recently replaced the original alternator with an ARCO 60125. This may be confusing because of wire colors. One is purple, the other is purple/red
With all the wires connected, it creates quite a draw on the battery (pulls it down below 8 volts) and blows the ignition fuse after a few seconds, whether cranking or just 'on'. The boat doesn't start. Completely disconnected the motor will start and run well.
If I leave the purple/red wire disconnected, it starts and appears to be charging, but the trim tabs don't work (I don't know if that's a separate issue or not) but I can't figure out why the battery load issue.
When I leave the purple wire connected as well as the Orange wire, and disconnect the purple/red wire, the engine turns but won't fire, which makes sense because the wiring diagram shows that it goes to the ignition coil.
I don't know if this is enough info, but I don't know where to start looking for the problem. There must be a short somewhere that's causing fuses to blow ... but if anyone can give me a direction or two to start looking that would be awesome.
Thanks,
Jim
Davis Island, Maine

 

[alldodge]

Howdy
Something is miss-wired and don't think its at the ALT, maybe at the trim pump or starter. Here is the OMC wiring diagram, and look thru to see if wiring is correct

 

[JimL111]

Alldodge,
Thank you so much. It's raining today, so it may be a day or two before I can get out to the boat, but in the meantime I will study this wiring diagram.
An interesting note is that I had a recent realization that the old alternator has not been charging. I have a minimal power demand and strong batteries. I think that's why everything else was working okay ... because the alternator was not. I'll post back once I've had a chance to get out to the boat and chase some of this wiring down.
-Jim

 

[JimL111]

Alldodge,
Quick question. Bear with me, but I'm thinking out loud so to speak.
I have not looked at the splice where the R/PU and the PU wire come off the alternator, so I don't know what the connection looks like yet. It must be in the rear of the engine because it's not out front near the alternator. But anyway, in seeing where the wires go, my initial thought is that the splice could be bad and the two wires are causing a short circuit with each other, or the PU wire got shorted to ground, allowing only the R/PU (red/purple) wire circuit complete.
Back near the distributor there is what I think is the ESA module. It has a purple wire and others going into it, but it's sealed. I assume that's the same purple wire coming from the splice. The ESA seems to be functioning properly, as I've not had any issues with it.
I'll be back.
Jim

 

[alldodge]

If the splice was shorted (R/PU and PU) then the ALT would not charge correctly because it cannot sense a difference. Don't see it causing anything to blow fuses

The ESA module is only used when going out of gear in the water, it isn't used when on the trailer

 

[JimL111]

Got it, thanks.

 

[JimL111]

Hi Alldodge,
I'm flummoxed, but I'm back. Sorry it's taken so long to be back, but it seems if it's not one thing it's two.
Here's where Im at: I think I have a loose connection behind the switch panel. I took it off the other day to check connections and fuses because the trim flaps were not working. I found that the flaps are not wired under the dash, so they must get their power in back of the motor. In checking the all switches though, I realized it was a bigger problem because I found that the engine room blower was the only thing coming on when tested.
There are 8 items on the switch panel: Nav Lts, Blower, Cabin Lts, Cockpit Lts, Horn, Bilge Pump, Water Pressure, and Accessory. Of them, only the Blower works consistently. All of the gauges work, as does the trim/tilt on the throttle lever.
After I put the panel back in, I started the motor, and for some reason everything started to work. It didn't last long, as it went back to just the blower. I'm reviewing the wiring diagram to see if I can find a sensible place to start checking connections.
Question: Do all of these items get their juice from the accessory circuit? The reason I ask is that my wipers were connected to it, and I removed two orange wires to get them both to stop operating when I turn my fish finder on. My Clymer says to check the 20 amp fuse between the ignition switch and the ammeter. That's not the voltage gauge, so I don't know where the ammeter is. There is an inline fuse on the big red wire between the battery and the ignition switch. When that blows, nothing works at all, so it's not that fuse. There's a photo in the electrical system section that shows me what they are talking about so that's where I'm headed next.
Any words of wisdom is appreciated. I'll be back.
Jim

 

[alldodge]

Nav Lts, Blower, Cabin Lts, Cockpit Lts, Horn, Bilge Pump, Water Pressure, and Accessory.

None of these should be power from the motor, they should have a separate supply and ground

From what your saying yours is not done like the pic below, but it should be

 

[JimL111]

That looks too neat! I'll take this down to the boat with me and see. There are a lot of wires and not much space to work behind the panel, as you can see below.
-Jim

 

[JimL111]

I'm looking at your last photo and do not see the ignition switch. My big red wire comes from the battery switch to the ignition switch. I had to replace my faulty ignition switch with a new one and a new inline fuse. This was the day I learned that without this fuse, nothing works, so I carry several spares. Take a look at the old one, whatever happened melted the fuse housing:

 

[JimL111]

Ok, so I’m on the boat. Each of the fuses has power. Some better than others, but mostly 12.1v. Now I think it must be a ground somewhere that is loose or came offf. Still plugging away at it

 

[JimL111]

Two bad 20A fuse holders coming off the battery switch got replaced but didn't change anything. I'm working my way forward from there. I wish I understood electricity better. The cigarette lighter/power port is grounded because it's what I used when checking for voltage on the switch panel. There must be another ground somewhere. Then again it shares a ground with the marine radio, and it does not work. Woe is me.