1978 Johnson 150 V6 wiring help

[A1SlowHand]

Howdy all,
I have seen where a ton of questions has already been answered on this site, and looked for the answer to my question. But could not find it so .....

I have a 1978 Johnson 150 model number 150TL78S and the Ser # is J5008633.

This history is this boat and motor lost froward gear while on the water. I assumed I probably needed to do some lower unit work. Time and money did not allow me to do that then. Now 4 years later I'm starting the task. I thought I would first turn the motor over to see if it had froze up while sitting. She turned over just fine. But I noticed smoke from the postive terminal on the battery. Sure enuff it was hot enough to burn the fingers.

So I started running some continuity testing. I was getting a continuity between the engine ground and the hot side of the starter soleniod when the ignition switch was in the on position. I then separted the red connection plug and seem to think the problem is in the ignition switch area. I have conntinunity between the red/purple and the purple wire when the switch is in the on position at the red plug terminals. Is this normal?

Any help, ideas, pointers, suggestions???? Shoot even a howdy right now would let me know I not alone. d

 

[Seasport]

Re: 1978 Johnson 150 V6 wiring help

Sounds like you just need to clean that battery connection and reinstall firmly. A poor connection will cause heat build up as you describe.

Are you getting smoke just when you turn the starter motor over (key in start posiiton) or does this happen all the time? If there is continuity between the hot side of the solenoid and ground (unlikely) the battery would be shorted somewhere and you would likely get smoke even if you do nothing.

The red/purple wire is the fused 12V supply from the battery. The ignition switch will link this with the purple wire when the key is in the run or start position. So yes this is normal.

 

[A1SlowHand]

Re: 1978 Johnson 150 V6 wiring help

Sounds like you just need to clean that battery connection and reinstall firmly. A poor connection will cause heat build up as you describe.

Are you getting smoke just when you turn the starter motor over (key in start posiiton) or does this happen all the time? If there is continuity between the hot side of the solenoid and ground (unlikely) the battery would be shorted somewhere and you would likely get smoke even if you do nothing.

The red/purple wire is the fused 12V supply from the battery. The ignition switch will link this with the purple wire when the key is in the run or start position. So yes this is normal.

The smoke only happens when the key is in the start (crank) position. The battery is a fairly new (3 months?) fully charged marine battery. Connections were tight, thats where I burnt by fingers. In the on position I have no smoke.

I had the hot wire disconnected from the battery when I was checking the continunity at the engine ground and the sloenoid, and the key in the on position.

Thanks for ruling the continuity on the red/purple and the red wire as normal. Maybe if I can rule out what is normal, what's left will be my problem.

 

[ezeke]

Re: 1978 Johnson 150 V6 wiring help

You need new battery cables.

 

[A1SlowHand]

Re: 1978 Johnson 150 V6 wiring help

I replaced those a couple of years ago with #4 welder cables. I thought those were the right gage to do the job.

 

[ezeke]

Re: 1978 Johnson 150 V6 wiring help

Electrical resistance always telegraphs by heat. When the heat is at the battery, the cables are almost always bad or inadequate in some way. The problem may be in the form of corrosion within the sheathing.

I think you should be using #2 marine cables.

 

[A1SlowHand]

Re: 1978 Johnson 150 V6 wiring help

OK I will see if I can't find some #2 cables tomorrow and give that a try. I will update after the change over.

Thanks.

 

[Seasport]

Re: 1978 Johnson 150 V6 wiring help

Agree - could well be a poor connection between the cable and the battery terminal. As ezeke says, high current (when operating starter) plus high resistance = heat. The heat is where the high resistance is.