Hey all, the people on this board have always helped me fix my trolling motor problems, Thanks for that, but know I got a new problem. I was out fishing in the middle of the Chesapeake and the wind picked up to about 25mph all of sudden, I was using my TM to keep me over a spot so I turned the power up all the way like I have many times before, about 15-20 minutes later the TM shut off, then I started to smell something burning so I looked in my anchor locker (where I have my TM wire plugged in) and the plug was on fire!!!

Is this unusual? or maybe I just ran the TM to hard for to long? should I be O.K. if I just replace the plugs and maybe the wires? thanks!!

Heres a pic after the fire

Stuff happens.  I had my TM switch croak after running it on full power for an extended amount of time.  Replaced the switch and never had a problem since.

Things wear out.  Replace it and keep an eye on it - especially if you're using it on full power for a long time.

There was no pick but sounds like you were running a connector that was bad or too small.  What ever the case, you definetly had a bad connection.   You may be one of the many that are going to these big trolling motors and fail to realize just how much heat is generated by too small of wiring, and too small of a connector or a bad connection.   I see people using their original 30/40 amp plugs that came in the boat and plugging 70 and 80 pound thrust TM into them and then wonder why the plug/receptical melted or is getting hot very hot.

An oxidized connector that only looks discolored can easily cause a 1/2 ohm resistance.   A 1/2 ohm resistance on a a large 24V TM running on high and pulling 50 amps is going to generate 15 watts of heat in that area.  Crab a small 15 watt light bulb after it has been on for a few minutes and see how big of a blister you get.   These big TM's everybody is going to these days need at least #4 battery cable (some sell it as marine cable) and a good 75 amp connector.  None of those twist lock things like you see in so many of the older boats.

Thanks for the replies!! The plug is actually the kind that minn kota sells for their TMs. Im going to try the pic again, Im actually lucky the boat didn't catch fire because it chared the inside of the anchor locker

I was running my 24v MK TM down the lake on high for an extended period when smoke started pouring out of the head unit. I had to turn the speed down to 4. The shaft had been removed prior to my buying the motor for a rebuild and the guy that redid the connectors didn't do a good job with the new splices.  The splice connectors were actually melting!  

As W2S said, those TM's at high speed really pull some current. If you've got undersized wiring or a bad connection anywhere in the entire TM circuit you've got the potential for overheating and possibly a fire.

Now you guys have me scared! Not to hijack your thread zam, but I think this is directly related to your post -

I got my new 50# trolling motor a couple of weeks ago (thank you cart7t!) to replace a 28# and started the installation. I ran new 8ga wire bow to stern (I was too cheap to buy the 6ga), and replaced the 30A manual reset breaker with a 40A auto reset. Then I noticed a few things when I started the bow connections. First, I would need to purchase new connectors for the TM since the socket end in the bow plate was molded. Either that, or I would need to run the wires through a hole in the plate and just do a permanent splice on the wires. I also noticed the insulation specs on both the existing 10ga and and the new 8ga. The 10ga was rated at 105 degrees C and the new 8ga was rated at 90 degrees C.

Now I have a conundrum! The 10ga is going to get hotter since you can only force so many amps down so many strands of wire before producing excess heat, but it can. The 8ga will not get as hot, but it can't anyway. Seems to me it is a wash.

Now, since I have finished the installation, I have been having nightmares about having a fire in the wiring. My wife and 6 year old keep asking when we are going fishing again and I keep telling them they cannot be on the boat until after I have taken it out and tested the new installation. I haven't done that yet since I would like to have someone with me to hand me the fire extinguisher and run the boat on the outboard close to shore while I fight the fire before we abandon ship.

Now it is possible that I am being overly paranoid, but I'm almost to the point of hiring an electrical engineer to advise me before I launch this thing again. I suppose that's what I get for trying to save $0.25/ft on the wiring. Any thoughts on this (other than me being cheap and foolish)? I would hate to have to add my own pictures to this thread. On the other hand, if I have to tell my wife the expense of redoing this all over again, I might as well take it out as is, let it burn, and just go down with the ship.

I recently got a tm for my larger canoe.

I did not use it until I got a circuit breaker to install at the battery.

Never skimp on wiring, and never use a circuit breaker that will allow the wiring to melt down.

Better to go heavy on the wiring, and use a lower amp breaker, than to skimp on wires and use a too high rated breaker.

Stuff does happen.

That's why we have safety devices.

Well, first off, any heat is wasted power so if the wire is getting warm you are running the TM at a reduced power but the battery is still putting out the current for a higher power.  What it boils down to, why buy a 50# TM if your going to run it on too small of wire that the resistance is going to 40# pounds of thrust because the other 10# is being wasted in the cable heat.    Same with going cheap on the connectors, if they are heating up, the TM is not producing full thrust and you're increasing the chance of a melt down.

Remember also, any time you're looking at charts for the proper size cable, with most of those charts you have to double the number of feet because you have two lenghts of cable, one positive and one negative.  If you have one of those 12/24 system at the front and four cable going back to the battery, you may have to figure four times the length, depending on how it's wired.

I run nothing smaller that #6 battery cable and if running large than 60# TM, I run #4.  I also use nothing but the Harrison Connectors, either the 50 amp on #6 cable or 75 amp on #4 for big motors.  I also run large heavy duty copper or silver plated connector that are crimped and soldered.

Now you guys have me scared! Not to hijack your thread zam, but I think this is directly related to your post -

I got my new 50# trolling motor a couple of weeks ago (thank you cart7t!) to replace a 28# and started the installation. I ran new 8ga wire bow to stern (I was too cheap to buy the 6ga), and replaced the 30A manual reset breaker with a 40A auto reset. Then I noticed a few things when I started the bow connections. First, I would need to purchase new connectors for the TM since the socket end in the bow plate was molded. Either that, or I would need to run the wires through a hole in the plate and just do a permanent splice on the wires. I also noticed the insulation specs on both the existing 10ga and and the new 8ga. The 10ga was rated at 105 degrees C and the new 8ga was rated at 90 degrees C.

Now I have a conundrum! The 10ga is going to get hotter since you can only force so many amps down so many strands of wire before producing excess heat, but it can. The 8ga will not get as hot, but it can't anyway. Seems to me it is a wash.

Now, since I have finished the installation, I have been having nightmares about having a fire in the wiring. My wife and 6 year old keep asking when we are going fishing again and I keep telling them they cannot be on the boat until after I have taken it out and tested the new installation. I haven't done that yet since I would like to have someone with me to hand me the fire extinguisher and run the boat on the outboard close to shore while I fight the fire before we abandon ship.

Now it is possible that I am being overly paranoid, but I'm almost to the point of hiring an electrical engineer to advise me before I launch this thing again. I suppose that's what I get for trying to save $0.25/ft on the wiring. Any thoughts on this (other than me being cheap and foolish)? I would hate to have to add my own pictures to this thread. On the other hand, if I have to tell my wife the expense of redoing this all over again, I might as well take it out as is, let it burn, and just go down with the ship.

You'll note on the TM end of the wire that I had those fittings installed.  I had the same installed on the ends coming from the battery.  That was installed on that aluminum boat I sold recently and I hard wired the TM in.  No TM plug.  In fact,  I haven't used a TM plug in some time.  I've hard wired my TM foot pedals and have never had an issue.  Your 8 gauge wire should be OK for the run to the TM though 6 is always preferable.  I used 8 on the aluminum boat though my distance running from the battery to the pedal was fairly short.  

I recently got a tm for my larger canoe.

I did not use it until I got a circuit breaker to install at the battery.

Never skimp on wiring, and never use a circuit breaker that will allow the wiring to melt down.

Better to go heavy on the wiring, and use a lower amp breaker, than to skimp on wires and use a too high rated breaker.

Stuff does happen.

That's why we have safety devices.

In the case in question, however, "safety devices" and a good working circuit breaker would not have prevented the fire.  When there is a dirty connection in a plug the current required to cause the fire is less than the current the trolling motor draws so the circuit breaker would not trip.

yep my circuit breaker never did trip on mine. After inspecting everything, the (male) plug thats connected to the TM wires was what caught fire, the wires to the TM also burned, but the wires that run from the batteries to the (female) plug (6 amp)still look like their in good condition..Im hoping to change the female and male plugs and maybe the wire to the TM and hopefully it won't happen again

All of the wire size advice given was right on. Don't neglect the connectors themselves. If the male to female connections are not tight, this too will cause excessive draw. These can be difficult to find as the terminals are often encased inside of connector bodies. Just because the two halves snap together securely does not mean the pins inside did the same.

Any plugs should receive a generous application of dielectric grease.  Good for light bulbs too.

Keeps out water and thus inhibits/prevents corrosion.  Makes changing bulbs easier.  Also makes connecting and disconnecting plugs easier as well.

Update! I replaced the plugs and ran the TM hard today for about 4 hours, and it never did get hot. it did feel a little warm at times but Im not sure, it may have been my imagination, or maybe the hot sun