What gauge of wire should I use to run from  my battery inthe back of my 14ft v-hull to run a 40lb thrust Powerdrive on the bow?

Thanks,

Andy

6 Gauge.  You might get away with 8 gauge, but if it were my boat I would go with 6.

Where is a good place to buy that size wire that won't break the bank?

Andy

It depends upon the size of your bank.    Copper is expensive these days.  Both Home Depot and Lowe's sell it.

Are you talking about using just ordinary THHN house wiring?  I was assuming that it would be more of an automotive style wire.

You can get it from Cabela's

http://www.cabelas.com/cabelas/en/templates/product/standard-item.jsp?_DARGS=/cabelas/en/common/catalog/item-link.jsp_A&_DAV=MainCatcat21276-cat21380&id=0017401015716a&navCount=2&podId=0017401&parentId=cat21380&masterpathid=&navAction=push&catalogCode=IH&rid=&parentType=index&indexId=cat21380&hasJS=true

Hey bud,

Make sure you use a fuse or in line breaker also.

You can get it from Cabela's

http://www.cabelas.com/cabelas/en/templates/product/standard-item.jsp?_DARGS=/cabelas/en/common/catalog/item-link.jsp_A&_DAV=MainCatcat21276-cat21380&id=0017401015716a&navCount=2&podId=0017401&parentId=cat21380&masterpathid=&navAction=push&catalogCode=IH&rid=&parentType=index&indexId=cat21380&hasJS=true

And pay a fortune.  People don't know this, but automotive wiring will work just as well there.  Not always as many strands, but unless it is getting moved a lot (like an extension cord) that is not a problem.

Compare them at the homecenter's and such. I find it unlikely that you are going to find automotive wire in 6 or 8 ga but check anyway.

If going straight to a trolling motor only, you don't need any larger than the wire size of the trolling motor or the wire size on the connector. You might keep in mind though that you probably add later so you need to have enough main feeder wire size to cover the sum of the currents.

If you will be in saltwater then marine grade is probably a must

That would be a whole different subject.

I had a 12 foot jon boat and ran 4 gauge from the battery in the back to the tm on the front. Within 1' of the battery you will want to put a fuse or a breaker. I like the breaker because if for any reason it trips you just reset it and you don't have to worry about carrying extra fuses. You can get the wire and breaker from most auto stereo shops. They will sale the wire by the foot and most stereo wire is flexible. Hope this helps. Good luck.

Tony

Compare them at the homecenter's and such. I find it unlikely that you are going to find automotive wire in 6 or 8 ga but check anyway.

If going straight to a trolling motor only, you don't need any larger than the wire size of the trolling motor or the wire size on the connector. You might keep in mind though that you probably add later so you need to have enough main feeder wire size to cover the sum of the currents.

Yes you do need larger than the TM.  The trolling motor lead is usually 2 feet long.  You can have a smaller gauge for a 2 foot run.  Unless your battery is under the TM, you need to have a longer run.  For that section, you need a larger diameter.  

For example, our wire feed 230 v welder has a 50 foot run, from the shop breaker box, to the door, then a 25 foot extension cord, and then the 5 foot cord on the welder itself.  For the run from the breaker box, to the roll up door, we have 8 gauge.  The extension cord is 10 gauge, and the machine has 12 gauge.  The machine has a factory installed 12 gauge, but if we ran 12 gauge all the way from the box, after 75 feet, it would loose a lot, and the cord would run hotter.

The same applies for trolling motors, just a lot fewer volts.

When I rewired my boat I bought a big ol set of jumper cables, cut the ends off and ended up with some really nice wires for my trolling motor

Are you talking about using just ordinary THHN house wiring? I was assuming that it would be more of an automotive style wire.

no do not use THHN ( it only has 19 strands)...go to an electrical supply house and buy welding cable or something similar. The welding cable will have hundreds of strands, be alot more flexible and since electric current is carried on the outside of each individual strand....something like welding cable will lessen resistance and handle the amp spike from starting the TM at full bore MUCH better than THHN.

THHN will heat under DC loads...heat causes resistance...resistance causes heat...yadda yadda yadda.

I was told by a MinnKota rep to figure about 1 amp for each pound of thrust ( @12 volts)

#6...is 60 amp wire and guarantees you will have the opportunity to upgrade later so it is a good idea. There difference between #8 and #6 is pennies per foot. In fact there are alot of days I buy #6 for LESS THAN #8 because of commonality. It is used more than #8 so that keeps the price down.

Compare them at the homecenter's and such. I find it unlikely that you are going to find automotive wire in 6 or 8 ga but check anyway.

If going straight to a trolling motor only, you don't need any larger than the wire size of the trolling motor or the wire size on the connector. You might keep in mind though that you probably add later so you need to have enough main feeder wire size to cover the sum of the currents.

This is 100% incorrect.  The longer the wire run the larger the wire you need to carry current without overheating.there are several charts that will tell you the proper wire size for the amperage and length of run. If you really want to get down to it it can matter if the wire is in free air, bundled, and steady or intermittent current.  

I really should have asked my question as How many amps will I be pulling with a 40 lb TM and just figured it out myself.  I do have several years experience with aircraft avionics and wiring mods on large aircraft.  I was sort of shocked when someone suggested the home centers beacuase as far as I know they only carry normal house wiring which is unsatisfactory for this application.  I thought that there may be some place that is widely know to carry the proper wire for a good price.  I had thought about car stereo wiring but I had not thought about welding cable, that is a good idea.

Bowtech182 - You're 100% correct in your final reply. Voltage drop is especially critical when dealing with low voltage DC current. I used a multiconductor 6/3 SOW cable (12/24volt system) available at all electrical supply houses. Never looked for it at HD or Lowes. I liked the fact that it was enclosed it one sheathing. Made it easier to pull through the hull cavities and was neater in the exposed areas. SOW is rated for Outdoor use and the strands are very fine.

If price isnt a problem I personally would go to a specialty automotive sound system store in your area and buy some 4awg battery cable and run it that way. The bigger/heavier the cable the less you will have to worry about losing power. As always dont forget to put an inline fuse or a circuit breaker on the positive feed in between the TM and the battery.

I lucked out because one of the avionics techs at work had 50 feet of aviation grade  4 gauge wire laying around his house, very high strand count and tinned conductors.  I also got a 50 amp button resettable breaker to go along with it.

Andy

I lucked out because one of the avionics techs at work had 50 feet of aviation grade  4 gauge wire laying around his house, very high strand count and tinned conductors.  I also got a 50 amp button resettable breaker to go along with it.

Andy

Sounds like your all set and pretty lucky for your friend with the extra cable. That does get expensive especially running 2 lengths the length of your boat.

sounds like some perfect world ideas but I think there is some serious overkill on the engineering front.

As an example keep in mind I'm a little rusty in my ET theory and might not even have my formulas right so feel free to double check me.

Using the resistance difference of lets say 8 ga to 6ga wire per foot

.000739-.000465= .000274 ohms diff / foot x 16ft of wire = 0.004384 total ohms

voltage drop is E(volts) = I(40 amps) x R(0.004384 ohms)= 0.17536 volts total drop

( give or take) on a 14ft boat .17536v/12=0.014613 = 1.46% loss

This is only applicable with the trolling motor on full 40amps

Car stereos and such comes into play as I think some are in the 200amp(?) range for the thumpers

As far as AC vs DC they don't put special DC wire in generic industrial cabinets vs AC wire. 14 feet is not a long run maybe 400 but not 14. High amperages and high voltages would have a larger effect such as longs runs for power plant distribution or an aircraft feeder as wire can run for miles inside an airplane.