Jumper wire burned/melted

vulcrider

Cadet
Joined
Jul 13, 2011
Messages
6
Hello all, new to the forum and have found great info! But, I cannot determine the cause of the following:
1991 Suzuki DT25C. Was backing the boat (16' Starcraft) to retrieve fishing line snag, saw that I might wrap fishing line around prop, placed in neutral and raised motor out of water. Was still running and noticed smoke from lower end. Found that the jumper wires from the clamp had burned! Touched the two ends together and saw spark/arc. Stopped the motor and before I could disconnect the battery, saw smoke from the tiller arm pivot. Disconnected battery and discovered the throttle cables had overheated and fused. Could not operate throttle so had to use trolling motor to return (5 miles, very slow!)
When replacing cables, saw that one had rubbed lower engine case. Checked all connections, grounds, wiring and battery cables. Saw no indication of shorts or damage. Checked battery, showed good. Test ran motor with Mickey Mouse ears and looked for indication of jumper wire overheat -- no problems. Ran motor in lake, worked great, but found the lowest jumper wire burned again. Replaced wire, tested charging system -- shows 13.5 - 14 volts, no spikes. I do get battery voltage showing at jumper wire (engine off) when connecting voltmeter from engine ground to jumper wire terminal. I cleaned anode area (anode is perfect), and am wondering if voltage should show at jumper wire.
I have many years experience with small engines (chain saws, lawn mowers, etc) but am a little lost on this outboard. I have factory service manual and have traced all wiring. The battery and wiring are all isolated from the hull and show no shorts or contact with it. Any ideas?
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,195
Re: Jumper wire burned/melted

I believe you are talking about the bonding wire that connects the lower unit to the center section. It is there to keep all of the motor tied to the anodes. If this wire is carrying current/voltage then you have a problem with the negative battery cable makeing a good connection to the motor and the current is trying to follow any path it can to get where it needs to go
 

vulcrider

Cadet
Joined
Jul 13, 2011
Messages
6
Re: Jumper wire burned/melted

I most definitley appreciate the reply. This is the same diagnosis that I came to, but cannot determine where the issue is. The main negative battery cable shows no unusual resistance and the grounds have all been cleaned and checked. Would it be wise to run a new or additional ground wire fron the ground terminal on the engine to the negative terminal on the junction block?
 
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