2001 Mercury Fourstroke EFI Melted wiring. What are these wires & why did they melt?

[mbhoag]

2001 Mercury Fourstroke EFI Melted wiring. What are these wires & why did they melt?

[h=2]2001 Mercury Fourstroke EFI - Melted wiring.... whats my problem?[/h] July 5th, 2016, 09:04 PM

Hey all, recently bought a new-to-me 2001 Proline19 Sport, with 2001 Mercury Fourstroke EFI... Although the boat itself has little impact regarding my problem, its still fun to tell people about it!

Took it on a small wake-only lake this weekend for her maiden voyage and shakedown... and discovered a couple of issues...

1) Since lake is small and no-wake, we did not get going much faster than an idle...which is actually nice if you are trolling...anyway, I noticed that the Tachometer usually read zero, with intermittent burst of activity...

This suggested to me the possibility of a loose tach connection someplace, or possibly a bad rectifier or voltage regulator (not sure which my motor has as of yet)
So I pulled the cover today to look for loose connections, and to my surprise found a melted wiring harness! (see pics). I was surprised that with all these melted wire the motor still ran like a dream.
It appears that the melted wires are confined to ground wires only, but of course its hard to see inside the harness.

I obviously need to figure out what this wiring harness is, and replace it.. I can only hope that it will resolve the tach issues, but my bigger concern is
A) what might have caused this? (could it be as simple as wires worn rubbing on hot motor parts until they finally shorted) or something bigger?
B) where can I find a replacement harness, and how to I figure out what part number it might be?
C) Can I safely cut and splice in new wire to replace the melted ones?

2) Also found one odd connector, that looks like it has been cut and shorted... is this jury rigged, or normal? (If jury rigged, what does it do?)

Thanks for the help, all suggestions and comments are welcome!

Mark

 

[mbhoag]

Just an FYI for those who may come across the same issue... I carefully pulled the elec connectors from the motor, and separated each wire from the melted coatings....As bad as everything looked to begin with, there was only 1 melted wire, and it was a ground!

I removed the bad ground from the plug to the block, and reinstalled a new ground (with a slightly heavier guage wire), sealed up any other wires that had sheathing damaged, and all is good. My guess is that the block connection was corroded for the ground, causing the wire itself to overheat and melt...making a heck of a mess, but no real damage was done.

Sometimes patience and further investigation can pay off!