Electrical short?

gregk9 · Sep 16, 2011

Can a bare cable ground wire that?s been rubbing against a insulated hot wire cause a short even though the insulation is not worn down to the bare wire?

This is what appears to be happening. It?s where the smoke?s coming from. The insulation is definitely melted. I'm just not seeing any bare wire. Even scraped it with my fingernail. Could the insulation have melted briefly then re-coated the wire?

HighTrim · Sep 16, 2011

Re: Electrical short?

You likely have corrosion, where there is resistance there is heat.

The wires corrode from the inside out. DO they crunch when you flex them....voltage drop test will quickly identify a problem.

gregk9 · Sep 16, 2011

Re: Electrical short?

So you're saying that the ground wire isn't a factor and I likely have corrosion at the point where the melting is taking place? I'll go see if they crunch. BTW, the outboard is 20 years old.

gregk9 · Sep 16, 2011

Re: Electrical short?

The wires aren't really crunchy.

V153 · Sep 16, 2011

Re: Electrical short?

gregk9 said:
Could the insulation have melted briefly then re-coated the wire?

Probably not, it doesn't work that way, but I do admire your optomism ... Greg yer gonna have to move a few parts out of the way & find the source of the short. You are correct there btw, when wires start smoking that usually indicates a short circuit.

Fed · Sep 16, 2011

Re: Electrical short?

Put up a picture Greg.

BTW, the bendix in your other thread (I hope a mod will combine these threads) should be in the down position at all times other than when actually cranking the engine over. Free it up & lightly oil it.

Missing insulation could be from a high resistance connection or high current flow in the wire. A picture & better description will tell the story.
Diagnosing this should only take a minute or so, seriously it's not rocket science.

gregk9 · Sep 17, 2011

Re: Electrical short?

Fed said:
seriously it's not rocket science.

But it is apparently. :facepalm:

Ok, I thought I did find the short, it's where the wire insulation has melted? or is it incorrect to assume this? But as HighTrim indicated, it could be a point of corrosion (is this considered a short?) and that's why melting of the insulation.

Like I said, there was a bare ground wire ( by design) rubbing against the hot wire right above the grommet on the lower cowling but under further inspection - no bare hot wire.

Incidentally, Theses are the wires that go to the trim motor. This has gotta be what causing the starter issues, yes? The short is sucking the current from the solenoid?

I couldn?t get a picture because of where it was located. I got the grommet removed and the wires pulled up so I can get at them. I?ll see what kind of picture I can get.

Oh, and the starter?s been rebuilt. I?m assuming low current is why it doesn?t drop back down? I can do it by hand.

HighTrim · Sep 17, 2011

Re: Electrical short?

I just found your other post regarding this.

I believe the first response to your question was to remove all connections regarding the battery, starter, solenoid, and especially ground and polish them to a shine with a file then retighten. Did you do this....

Short of that, there is likely faulty wiring somewhere in the system. Do you know how to do a voltage drop test to locate this, if not we can help you with it.

gregk9 · Sep 17, 2011

Re: Electrical short?

HighTrim said:
I believe the first response to your question was to remove all connections regarding the battery, starter, solenoid, and especially ground and polish them to a shine with a file then retighten. Did you do this....

Not once but twice.

I'm not sure about the voltage drop test but wouldn't the problem be where the melting is taking place?

gregk9 · Sep 17, 2011

Re: Electrical short?

Most of the melting is on the black insulated cable. A little bit of the mesh covering the blue wire melted. And a bit of the crusty white came off the other blue wire. The blue insulation was not affected on that one. In their original position, this wire bundle is stuffed back down in that hole, inside a grommet and that bare ground wire is right up against them.

Fed · Sep 17, 2011

Re: Electrical short?

From your other thread...

Connections have been cleaned, starter and solenoid have the correct voltages.

How many Volts between the Positive stud on the starter motor and your engine block when the key is turned to the start position?

Push / twist the bendix gear up & down by hand, apply a little light oil and work it until it's completely free & drops down by itself.

It's NOT the trim wire causing your problem.

http://forums.iboats.com/showthread.php?t=488429

Fed · Sep 17, 2011

Re: Electrical short?

It's a little hard to see in the pic Greg but it looks like the bare ground strap has been getting hot, are you sure you had the correct voltage at the starter motor when you tested it?

I'm thinking bad ground on block causing the ground strap to try & carry the starter motor current, this will show up as low voltage at the starter motor in the test I asked you to do in the post above.
Is this an aluminium boat?

gregk9 · Sep 17, 2011

Re: Electrical short?

Fed said:
It's a little hard to see in the pic Greg but it looks like the bare ground strap has been getting hot, are you sure you had the correct voltage at the starter motor when you tested it?

I'm thinking bad ground on block causing the ground strap to try & carry the starter motor current, this will show up as low voltage at the starter motor in the test I asked you to do in the post above.
Is this an aluminum boat?

I was going to recheck the voltages at the starter and solenoid but get this; I hooked everything back up, reconnected the positive lead on the starting battery; turned the key and the starter cranked like normal ( no more smoke either). Tried it a few more times and it's working fine.

What I did not do was stuff all those wire back down to the bottom against that bare ground wire.

You?re right, that bare ground wire has to have been getting hot. All the burn marks on the insulation indicate this. I peeled back the outer insulation so I could inspect the insulation on the individual wires and it?s fine on all of them. So this melting of the insulation is coming from the outside.

About the bad block ground causing ground strap current - this wouldn?t be present as long as the starter is working, correct?

And yes, it's an aluminum boat.

Fed · Sep 18, 2011

Re: Electrical short?

You may have inadvertently fixed it Greg but now we don't know where the problem was/is and how good the fix was.

How many wires are on the positive battery terminal & where do they go?
How many wires are on the negative battery terminal & where do they go?
How many Volts between the Positive stud on the starter motor and your engine block when the key is turned to the start position?
Where does each end of the hot ground strap connect to?

gregk9 · Sep 18, 2011

Re: Electrical short?

Problem was a ?hot? ground strap, no? You mentioned that a bad ground on the block could cause the ground strap to try and carry the starter motor current and it would show up as low voltage at the starter motor. That would not be the case when the starter is working correctly, correct?

I wanted to get out there and try to start it again today but it?s been raining all day. UGH!!!

And what did I do besides keeping that ground wire and the bundle of wires apart to make it work now? Surely that alone didn?t ?fix? it. The only other thing I can think of is that I had all those ground wires off the block terminal and put them back on ?..maybe it?s one of those wires - not due to a connector being dirty but maybe a bad connection between wire and connector?? I?ll closely inspect those again?probably not ?till tomorrow. Looks like the rain won?t end until late tonight.

I?ll be able to get that other info tomorrow too.

Thanks!!

Fed · Sep 18, 2011

Re: Electrical short?

Problem was a ?hot? ground strap, no? You mentioned that a bad ground on the block could cause the ground strap to try and carry the starter motor current and it would show up as low voltage at the starter motor.

Yes.

That would not be the case when the starter is working correctly, correct?

Not necessarily, now your main negative cable & ground strap may be sharing the current and it will still be good enough to spin the starter.

And what did I do besides keeping that ground wire and the bundle of wires apart to make it work now? Surely that alone didn?t ?fix? it.

You're right, that wouldn't fix it.

The only other thing I can think of is that I had all those ground wires off the block terminal and put them back on

That may have fixed it, just disturbing the connections can 'fix' them for a while, like hitting your battery lugs on your car.
BTW, notice the corrosion around the ground stud & the block?

The bottom line...
The ground strap shouldn't be carrying the current and by getting hot it tells me that it is.
All the current should be going through the main negative cable back to the battery, I suspect you have a secondary negative connection through your hull back to the battery.
Don't think you've fixed it & move on, instead think about electrolysis and aluminium hulls & stick with it.

gregk9 · Sep 18, 2011

Re: Electrical short?

Fed said:
Yes.

BTW, notice the corrosion around the ground stud & the block?

yes but that stud goes into the block so that shouldn't be a factor, right?

Fed · Sep 18, 2011

Re: Electrical short?

It's probably just a little corrosion but I thought it worth noting, although the stud goes into the block it may not necessarily have a good electrical connection to the block.

gregk9 · Sep 19, 2011

Re: Electrical short?

Here's what I got so far this morning:

At the solenoid:

12.5 volts
9.5 volts when cranking.

At the starter:

0 volts
10.2 volts when cranking

Starter's working fine!

This is where the other end of the ground strap goes; right where that HH bolt is head is:

This is one ground I missed when checking all the contacts....that's next!

gregk9 · Sep 19, 2011

Re: Electrical short?

Fed said:
I suspect you have a secondary negative connection through your hull back to the battery.

I'm not seeing this. Could it be the one leading to the point in the picture above?

Electrical short?

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