trolling motor fuse got really hot and started smoking

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mrjames999

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Joined
May 22, 2008
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7
My minnkota trolling motor was working pretty good on my boat i just purchased this spring until smoke started billowing from the bow battery compartment. It has a 20 amp fuse between the TM and battery which melted profusely instead of blowing itself. I don't know why the fuse didn't protect anything. Should I just replace the fuse with a good size circuit breaker? Any help would be great thanks.
 
NYBo

NYBo

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Oct 23, 2008
Messages
7,107
Re: trolling motor fuse got really hot and started smoking

I would carefully check the wiring from the battery to the trolling motor. Did the fuse itself melt or was it the fuse holder?
 
ajgraz

ajgraz

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Re: trolling motor fuse got really hot and started smoking

20 amp doesn't sound like enough for a trolling motor, but more important I can't see why that wouldn't blow before something heated up enough to burn/smoke.

What size is the TM? What gage is the wire? Are all the wire connections good? Is the wire corroded? Is/was the insulation all good? What exactly burned? Something's wrong that made it burn before blowing the fuse.
 
Silvertip

Silvertip

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Re: trolling motor fuse got really hot and started smoking

Even the smallest trolling motor pulls more than 20 amps of current so a 20 amp fuse is too small. If that fuse didn't blow than the wiring to the trolling motor was too small for even a 20 amp load. The smallest wire that should be used is #8 gauge. Bigger if the battery is located in the back of the boat. Make sure the connections at the battery are clean and tight. Do not use that rig again until you get it sorted out as you risk a fire. And by all means, post what size motor you have so we can recommend proper fuse or circuit breaker.
 
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mrjames999

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May 22, 2008
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Re: trolling motor fuse got really hot and started smoking

It is 40 pound minnkota. The wiring is 10 ga and looks pretty good. the fuse holder is what mainly melted. The first time I used the TM I pulled the fuse out and the terminals were a little corroded. This is on a 2002 sylvan 16' that I believe came wired for the trolling motor from the factory. The previous owner didn't use the trolling motor at all so I think it has few hours if any. I bought a 40 amp self resetting circuit breaker for it today
 
ajgraz

ajgraz

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Re: trolling motor fuse got really hot and started smoking

There had to have been something completing the circuit across the fuse...maybe some kind of semi-conductive corrosion so bad inside the fuseholder (or maybe saltwater?) that the current bypassed the fuse.

40 amp breaker should be OK. 10 AWG should be OK, so long as the run is not more than 4 or 5 feet (8-10 ft roundtrip). Been running that very arrangement on a 54lb 12v TM for years no problem. If the run is longer than that, I agree 8 AWG or bigger.
 
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mrjames999

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Joined
May 22, 2008
Messages
7
Re: trolling motor fuse got really hot and started smoking

I'd say the wire runs 3 to 4 feet one way. Just charged the battery back up and I will try the new hook up sometime this week if work lets me. Thanks for all the tips and advice guys. this forum rules!!
 
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TerryMSU

Senior Chief Petty Officer
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Jul 31, 2007
Messages
743
Re: trolling motor fuse got really hot and started smoking

mrjames999 said:
It is 40 pound minnkota. The wiring is 10 ga and looks pretty good. the fuse holder is what mainly melted. The first time I used the TM I pulled the fuse out and the terminals were a little corroded. This is on a 2002 sylvan 16' that I believe came wired for the trolling motor from the factory. The previous owner didn't use the trolling motor at all so I think it has few hours if any. I bought a 40 amp self resetting circuit breaker for it today
Click to expand...

The fuse holder failed because it got corroded. That increased the resistance of the fuse holder connection. power = heat = Current*current*resistance. The fuse did not fail, the fuse holder did.

Actual fuses failing (as in failing to open when they should) is EXTREMELY rare. Unless you got one of the bad fuses from Harbor Freight, I doubt that the fuse was the failure point.

TerryMSU
 
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