Never seen this. Need the gurus

[fireman57]

1982 50hp evinrude. Have had this engine for 15 years and never any trouble. Went on a 4 day fishing trip and no problems the first day. Late in the second day I smelled something hot and when I took the cover off my shift cable was melted with the wire exposed and it was HOT. I have a wiring harness on it that had an extra black/yellow kill wire on it that I have capped off for years and it was laying against it. I assumed that it somehow arced into the shift cable and melted the covering off it. Isolated it and had no trouble after that. The engine ran and idled fine all day.
Day two the battery was a little low so I switched to my spare. Sure enough that cable got hot again. I have the old two handle remote so there is no electric in it. Just the throttle and shift levers. I wrapped it so it wasn't touching the engine cowling and ran the rest of the day. The third day my battery was dead that morning so there is a short somewhere in the system. My battery cables are fine, no cracks or issues there. Charged a battery and went back out. Now my throttle cable melted along with the shift cable. Also, the ground wire from the wiring harness is melted. Gave up and just came home. Put another wiring harness on and even with the key off when the bare shift cable touches the cowling it gets hot and even glows. Needless to say I have unhooked the battery. If I leave it hooked up it is dead by morning.
Could a bad rectifier cause this? Out of ideas or possibilities that make sense.

 

[jakedaawg]

All I can say is wow. I am thinking I would have to have this one at my shop I've got no clue

 

[gm280]

I think I understand what you are saying, but could you provide a few pictures? Obviously there is current flowing or those cables would never get hot and glow. So first thing you seriously need to do is see where the circuit loop is happening. It sounds like there is a direct positive voltage on the cables and any time they touch any ground that path it completes a circuit and very large current flows. I would search for the cables touching a positive lead somewhere and causing your problem. But that is just my opinion not being there and testing things. JMHO!

 

[Peter Eikenberry]

I would agree with GM. You have a short to ground. It is heating the wires and killing your battery. This is going to take some serious diagnostics with a multimeter to find. Considering how old this engine is I would suspect the insulation on the wiring is deteriorated and leaking current. Which wire, where? Like I said, take a multimeter and start checking for grounds.

 

[fireman57]

I cleaned and redid all the grounds when I changed wiring harnesses. There is no hot wire close to these cables.I have checked my battery cables and they are all fine. No nicks or anything. I am going to start at the battery cable that connects to the solenoid and go from there. The battery drains overnight but the cables were burned by the pulse from the charge coils to the plugs.Just hoping that one of you had seen something like this before. The strange thing is it doesn't affect the engine performance while it is running.

 

[boobie]

Have you changed the battery cables ??

 

[fireman57]

I did a couple of years ago.

 

[F_R]

There is no way the ignition system could generate enough power to do what you are saying. And even if it were, it would not run. Somehow, battery power is flowing through the control cables. I have no clue how that is happening. As a place to begin, I suggest you completely remove the control cables from the motor and see if you still have battery discharge.

 

[Vintin]

Wonder if it's a bad ground and the motor and starter are getting ground via the cable?

 

[jakedaawg]

Wonder if it's a bad ground and the motor and starter are getting ground via the cable?

This makes some sense except that how would it get ground thrugh cables that have no ground in remote control? At barrels maybe?

 

[StarTed]

This sounds like something to use an ammeter while diagnosing. Connect the ammeter in series with the battery and start disconnecting things until the current drops. You have to be very careful using an ammeter because any connection across voltage and "puff and smoke". You also need to be sure that you don't exceed the capacity of the ammeter. Some multimeters have a shunt inside that can handle up to 10 amps. Don't exceed that.

You might as an alternative try a voltmeter in series with the battery. Any voltage reading will show a current drain. The problem with this is that the extremely high impedance of digital multimeters will give a voltage reading with very little current flow. Add a resistor in parallel with the voltmeter will lower the impedance and may give you better results.

Hope this is clear.

Good luck finding the load (drain).

 

[fireman57]

Thanks for the responses. Will try everything above today as long as I can handle the 110 heat index. Will revisit all grounds first.

 

[fireman57]

Just out of curiosity what do the yellow, yellow/white. yellow/blue wires on the rectifier do? I know they go to the stator and turn ac into dc but that is all. Just wondering if they could cause this problem.

 

[fireman57]

Okay, grounds on engine are good. Decided to focus on ignition switch. Had a semi weak ground on it. Fixed that. put the old shift cable that was burned up and am getting 12volts through the center wire of it with it not even connected to the remote, just connected to the engine and the other end laying over the boat. I can go from the center wire of it to ground and get 12volts. makes no sense to me. All this was with the key off. I started the engine and let it run for 20 minutes and the shift cable never got hot but showed 12 volts then also.

 

[interalian]

12V reading on a digital multimeter may be misleading as they are extremely sensitive. Can you apply a load like a light bulb between the shift cable and ground? Does it then light? If yes and the lamp glows, you have some current. If no, might just be milliamps. Very strange problem though.

 

[fireman57]

I could actually feel it tingle when I grabbed it and touched the pontoon fence so I know there is current there. what is so strange is that the engine never touches metal to transfer current to the fence or boat. Transom is wood onto aluminum and steel channel reinforcement. Going to check wiring harness under boat for fraying/breaks in positive.

 

[F_R]

Unless you have antique cables, they are plastic except for the center wire. And with plastic ends. Battery voltage is getting to that center wire somehow. That is a real mystery how that can possibly happen. I wish I knew the answer, but it beats me.

 

[jakedaawg]

You have a hot lead going to ground soewhere in the motor. Possibly through the starter. Remove starter hot lead at starter.and recheck your cable.also cheack battery cables any where they touch anything.

 

[oldboat1]

reversed battery polarity? Maybe running with a battery switch, and multiple batteries, one with reversed polarity or reversed at the switch?

 

[fireman57]

when I switch batteries I physically change the cables with the engine off.
As far as the cables they are the twin cables that split at the engine. No nicks or anything that I can see from the battery to the starter.Going to run the coating on the wiring harness back to the engine for breaks.