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Author Topic:   Wiring Trolling Motor
Landlocked posted 03-18-2009 10:40 PM ET (US)   Profile for Landlocked   Send Email to Landlocked  
I'm adding a Group 27 battery to my console to power my trolling motor and house circuits. I already have a combo start and deep cycle Group 24 battery in the console. I've cut a hole, installed the battery box, and purchased a battery selector switch (1-BOTH-2-OFF). I was setting everything up tonight and had planned on running some 6-AWG wire from the common terminal on the selector switch through the tunnel to my stern mounted trolling motor when the following thought occurred to me:

I ran heavy 2-AWG battery wire through the tunnel a couple years ago to the motor from the combo battery in the console. The positive lead of this cable will now obviously be connected to the common terminal on the new switch and the two batteries wired in parallel. Thus, the cables will be "hot" regardless of the selector switch setting. Why can I not tap into those at the motor end to power my trolling motor rather than running new wires?

Specifically, I was considering, hooking leads to the bolts on the engine ground and the solenoid and essentially using the motor as a junction box. I have enough 6-AWG wire to accomplish the task and I think I would end up with a very neat and shipshape looking install. What am I missing? I'd estimate I have about 10- to 12-feet of 2-AWG wire carrying current to the motor. The 6-AWG going to the trolling motor plug would only be about four feet long.

This seems too good to be true so something has to be wrong with the idea. Someone tell me what it is before I screw something up.


high sierra posted 03-19-2009 12:04 AM ET (US)     Profile for high sierra  Send Email to high sierra     
Landlocked, you could do it that way but I've never seen it done. Might not be a bad idea to try.
jimh posted 03-19-2009 07:40 AM ET (US)     Profile for jimh  Send Email to jimh     
On most outboard motors the terminal post where the primary battery positive lead connects is used as a distribution point already, and there typically are several terminals placed on that threaded post. I suppose you could argue that one more won't make a difference. You will end up with an extra set of battery cables running from the engine. The extra cable might not fit in the cable grommet, and it might interfere with steering.

From an operational point of view, it is better to isolate the battery that is operating the trolling motor from the battery that is to be used for engine starting. You should maintain the engine starting battery with strong charge so you can re-start the main engine. If you run the battery down with the trolling motor, you won't be able to start the engine. You could manage this by using the battery distribution selector switch to always change to the deep-cycle battery when you are operating the trolling motor, but that technique will depend on the operating being diligent. If you leave the switch in the BOTH position you will run down both batteries, and you might be in a pickle with not enough battery power to crank over the starter motor on the main engine.

It would be better to maintain some isolation between the engine starting motor battery and the trolling motor battery. You should install an automatic combiner relay or a dual charging accessory to keep them both charged when there is charging current available.

Landlocked posted 03-19-2009 10:06 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
I've checked the post and there are a couple of accessories/engine system wires jumped off of it already, but there is plenty of length on the shaft of the screw to Handle one more ring connector. Frankly, I hadn't thought about the rubber grommet - will have to check.

I use my trolling motor only intermittently. However, I'm installing the selector switch specifically to allow me to isolate the new Group 27 when trolling. I am used to having these switches on my work boats so I'm confident I won't forget to switch it over - at least not for long enough to run down both batteries. Switch will be set to both normally so that both batteries charge off the motor when it's running. I'll select the Group 27 only when the boat is anchored and I'm fishing at night running lights or when I'm using the trolling motor.

The advanatages I see to this approach:

1 - I spent considerable money running the #2 guage cables from the console to the motor. I quite frankly can't afford to run another set of #2 and would probably run #6. Even with this - my local mom and pop boat shop is charging me 1.50/ft for the wire and they won't even crimp the ends... I know I know - its not that much but it's the principal of the thing. Will save the story for a future rant.
Anyway I feel like Number 2 would obviously be better over such a long distance and if I can use what's already there - why not? By doing this - I would have #2 From the battery to the motor and then only about 4 feet of Number 6 going to the trolling motor.

2 - I already have an awful lot of wire, fuel lines, and control cables, running through the tunnel. this would save shoe horning another another set and would reduce the number of wires on the common post of the new switch.

Landlocked posted 03-19-2009 10:09 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Forgot to say thanks for your help.



Dick E posted 03-19-2009 07:41 PM ET (US)     Profile for Dick E  Send Email to Dick E     
Do not forget a circuit breaker on your wiring for your trolling motor. Should be about 60 amps.
Landlocked posted 03-19-2009 10:14 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Thanks Dick.

Actually looked at one today at Acadamy - manual says 50. They had both 30's and 50's for 45 bucks.

Spent the night at the shop.

1. Decided to mount the battery selector switch on the inside of the console ( Front just inside small door) No room on the plywood shepards crook backing and it was too far from the door to reach comfortably anyway so I cut up a small poly cutting board. Ran 4 - 1/4 inch bolts through from the back and put nuts on them to hold them to the board. Put a little Marine Epoxy under nuts - they'll never loosen... Switch slides over the bolts and then another set of nuts secures it in place. Rather than drilling any more holes in the console, used a whole tube of Epoxy to glue the cutting board to the inside of the console. Looks great. Time will tell if it will actually hold. But, if it falls while underway - no chance for a short.

2. Went ahead and hooked up the wires to the motor to carry power to the trolling motor. There were actually 3 unused holes in the rubber grommet. they fit through nicely.

3. Tomorrow, I'm going to by a small waterproof junction box to hold the breaker and a female receptical for the trolling motor. Box will be mounted in the back of the boat near the motor. I know breaker should be near the battery but I can't for the life of me figure out how to make that work with the setup I've chosen. I think I probably need more than a 50 amp breaker for the starter So I'm just going to put it on the lead going from the gas motor to the trolling motor.

It's been a fun couple of weeks. Wood's re-finished, batteries are installed, trolling motor is about ready to go. And I'm about done just in time for spring. 65 here today.

Looking forward to next weekend on the water. (Of course, it'll probably be 45 and raining... That's spring in Tennessee.


Dick E posted 03-19-2009 11:06 PM ET (US)     Profile for Dick E  Send Email to Dick E     
These work fine and will save you a bunch of money.
http:/ / cgi. ebay. com/ ebaymotors/ TROLLING-MOTOR-CIRCUIT-BREAKER-50-A MP-12-24-VOLT_W0QQitemZ400032158882QQcmdZViewItemQQptZBoat_Parts_Accesso ries_Gear?hash=item400032158882& _trksid=p4506. c0. m245& _trkparms=65%3 A1%7C39%3A1%7C240%3A1318#ebayphotohosting
Landlocked posted 03-20-2009 09:25 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Thanks for the tip! Hadn't seen anything like that.


Landlocked posted 03-20-2009 04:45 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Final question - I hope. Did a search, can't find the answer.

I have a 6 amp minkota on board charger. Now that I have two batteries rather than 1, could I attach the positive lead of the charger to the common bolt on the new switch and the negative lead to one of the batteries and expect both batteries to charge. there is typically a week between my usage of the boat so there would be plenty of time for charging. Only problem I see with this is that switch would have to be in the both position to charge.

Alternately, is there anything wrong with just hooking the chargers like normal up at the same time (one to each battery). I know there are dual bank chargers out there but I already have 2 good onboard chargers meant for single batteries. I'm guessing in this case I'd have to make sure the switch was in the off position when charging.

I guess I could unhook the supply cables and the negative jumper to be safe but that would be somewhat of a pain.


Landlocked posted 04-06-2009 11:11 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     

I ran the trolling motor wires to the motor as previously described and it works perfectly.

I found a marine junction box at my local big box home store and installed a solid front on it. Drilled a hole in the face plate to accept a standard trolling motor receptical. Sealed the whole thing up with 5200 and painted it white and then screwed to the stern just under the trolling motor. Sealed the end where the wires go in with marine epoxy (waterweld)

Completed install looks great and seems to work just fine.


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