12-volt battery entension cord

[Rich Jones]

I've got a 14' Sam Devlin Cackler stitch and glue boat that I use for fishing. In order to get the thing up on plane with my little 15hp Merc, I have to put the battery for the trolling motor up in the bow. To use the trolling motor, I then have to lug it back to the stern. The boat was rarely used up to this point, so it wasn't a big deal. But now, it'll be used a lot more.
The lights don't go on in my brain very fast and it's only taken me 10 years to realize that all I need is an extension cord and mount the battery under the foredeck permanently.
What gauge wire would I use? Can I just run a piece of 12-2 or 14-2 household wire or does it have to be something special?

[MiddleAgesMan]

I don't know what sort of amps trolling motors pull but my gut feeling is that 12 gauge wire is not big enough for even a short run. Check the specs on the motor, and while you're at it, see if the owner's manual specifies the wire size which will probably vary by length of the run.

As for regular house wire, don't use it. Get some good tinned marine wire once you figure out how big it needs to be.

[TerryLL]

First thing you'll need to know is the maximum current draw of the trolling motor and select wire that can handle the load. A starting point will be the size of the wire on the motor.

Bear in mind that the longer the wires, the less current will be delivered to the motor, because the wires themselves consume some of the current as heat. The larger the wires, the lower the heat loss.

Finally, you will want to use a stranded two-wire pair, not solid wire used in residential circuits.

[Figment]

I may be underthinking it, but I'd take a set of jumper cables and replace the alligators with lugs.

[Chip Chester]

Lots of folks like the trolling motor up front, too. Your preferences and boat details may impact that suggestion, though. Chip

[seo]

Solid "Romex" wire isn't "code" for boat use, because it tends to work-harden and break when subjected to vibration. That said, if the Romex is: a) copper, not aluminum, and b) carefully mounted, or run through a conduit so that it doesn't get tweaked, bent, stepped on, or vibrated, it might last a good long time. The other question is how much current your motor draws. Here's a chart:
http://www.affordable-solar.com/Lear...ls/wire-sizing
that will allow you to figure out what size wire you need for a given length and 12V current draw.
All things being equal, you might be better off with stranded wire, but it does cost more.
One problem with cheating on wire size is that it results in voltage drop at the motor, which results in reduced power output, shortened motor life, and means that your battery will waste a certain amount of its energy heating up your wire, as opposed to pushing your boat.
Have you considered mounting your trolling motor up forward, the way they do on some bass boats? Or moving your gas tank up forward. Or getting a tiller extension so that you can move forward a thwart.

[Rich Jones]

I may be underthinking it, but I'd take a set of jumper cables and replace the alligators with lugs.

I was thinking just the same thing. Jumper cables seem awfully big, but I guess they're big for a reason. I'll probably go that route to be on the safe side. It's just a fishing boat, so it doesn't have to be pretty.

[kc8pql]

This is really pretty easy to figure out. As stated above, you just need to know what the maximum amperage of the motor is. It's probably marked on the motor somewhere. If not, search the net for the manual, if you don't have it. It should be in there. Here's a link to a wire sizing chart. Once you know the amperage and the length of the wire run, use it to find the proper wire size (AWG). Note that the length of the circuit is the distance from the battery to the motor and back to the battery.
http://bluesea.com/viewresource/535

[MoMan]

I may be underthinking it, but I'd take a set of jumper cables and replace the alligators with lugs.

That's exactly what I did. It's a run of probably 5 feet, for a 30lb thrust Minnkota Endura on a 500lb fiberglass Mutineer. My biggest issue is accidentally unplugging it, which became a safety issue one day when I really needed some upwind thrust on a flooding river. I'm currently using a household plug (I know--not marine code). I'm making a run to West Marine today and hope to find something that locks together. I suppose I should check the amperage draw on the motor, but the jumper cable guage is significantly thicker than the motor wiring.

[JimD]

I did this with our trolling motor. Went to an automotive supply store. Can't remember what gauge we used but we just went up a gauge from what was originally on the motor. The wire comes on separate spools, a black one and a red. They even did the splice for me with heat shrink although its easy enough to do yourself. Worked fine.

[wizbang 13]

Is the trailing edge of the boat "sharp" or radiused, rounded off a bit.
I helped "Coffee Trader " a few years ago, with his Devlin Pelicano. He was un happy with the boats performance, did this simple thing, and planed off quicker, went faster, and saved fuel.
S n G boats are always rounded off for the tape, so the sharp transom has to be retro added. I have observed several Devlin planing boats plowing along , not lookin too good underway. Perhaps Sam is not "up to speed" on speed.

[Peter Malcolm Jardine]

All the right answers have been stated by Seo and Kc8.
Last but not least, you need to use marine grade wire. Wire that is not zinc coated will degrade more quickly than you think, and it can seriously compromise current transmission, and damage things. The wire isn't cheap, but there's a reason for that. By the book, (ABYC) you should have a fuse between the battery and the trolling motor too.

[Breakaway]

Yeah. what SEO and KCq* said. Use tinned copper, stranded cable. Here's a handy size/ampacity/voltage-drop link: http://www.acbsphl.org/Tips_and_hints/ABYC_Wiring.htm

Catch 'em up!

Kevin

[MoMan]

Does fresh water environment vs. salt make a difference in the need for marine wire?

My crappy little glass sailboat has been restricted to fresh water use, and as seldom as I use the $99 trolling motor, I can't justify the expense of marine grade wiring. But someday I will build a much nicer wooden vessel that I will be proud of, and then I will use only the best. Promise! Until then, my jury-rigged jumper cables will have to suffice.

[Breakaway]

marine wire, known as "boat cable" is:

stranded, not solid: so doesnt work harden and tales bends better

tinned: coated to prevent/inhibit corrosion

high temp: more fire resistant-rated to 105 C

Kevin

[Michael D. Storey]

I may be underthinking it, but I'd take a set of jumper cables and replace the alligators with lugs.

This is a good solution. Not only are you looking at adequate ampacity, you are looking at a multi-strand cable, which, unlike 12-2, will resist breaking as the vessel flexes, which I have been led to believe boats do.

[Rich Jones]

Just took the boat out fishing with the wife. I used the jumper cables, but they're really in the way. So, I'll use the charts you guys gave me and order up the correct wire.
Meanwhile, I'll take wizbang's advice and sharpen that transom bottom edge. The boat was designed with the motor in an open well at the back of the boat. This caused a lot of turburance and since then I've closed that off and put on a regular transom. It does put the engine 18" further aft, but I think it performs better even though all that engine weight is shifted aft.

I've put trim tabs on the boat and I think they help a little. Should they be parallel to the water or to the bottom of the boat? Boat has a slight V-hull.

[seo]

Based on the original poster's address, my guess is that he's on fresh water, which very much reduces the need for tinned marine wire. And as he points out, it's just a fishin' skiff.

[Mike Vogdes]

Is the trailing edge of the boat "sharp" or radiused, rounded off a bit.
I helped "Coffee Trader " a few years ago, with his Devlin Pelicano. He was un happy with the boats performance, did this simple thing, and planed off quicker, went faster, and saved fuel.
S n G boats are always rounded off for the tape, so the sharp transom has to be retro added. I have observed several Devlin planing boats plowing along , not lookin too good underway. Perhaps Sam is not "up to speed" on speed.

I believe the plans show a planing wedge at the trailing edge of the transom, seems most people ignore it...

[Phil Y]

Auto parts stores sell big fat wires that kids use to install huge amplifiers in their cars. These are quite good for large current applications.

[Rich Jones]

Just dug the plans out of the file cabinet. I remember the planing tabs from when I built the boat. Problem is that Devlin just drew them in on an elevation plan of the boat with no dimensions or at what angle to install them. That's why I left them off and installed trim tabs that I can adjust.

[seo]

With about a quart of plain old cheapo "Bondo" autobody filler you can experiment with planing wedges. Start out with, say, a 1.5" wide by 5/8" "high" (at the stern edge) wedge, and try it out. Grind it down if it seems like too much, goop on some more if you'd like some more. My guess is that this will be more effective than trim tabs in getting the boat up on a plane. Because the wedge has a longer chord, it maybe doesn't create as much drag as trim tabs?
Once you've established the size and shape you like, you can always grind off all the Bondo and replace it with a hand-fitted wooden wedge, made out of Pundingy wood harvested in the headwaters of the Amazon, and finished with 36 coats of varnish.
Also, you might try what I think are commonly called a "DoelFin," which is a plastic horiztontal fin that bolts to cavitation plate on your outboard. They help the boat get up out of the hole, at the expense of a little bit of top-end speed.

[mcdenny]

If the battery is 12 feet away from the motor, it pulls 40a max and you can accept 3% power loss due to wire resistance you need 6 ga wire. I get mine from genuinedealz.com.

[Mike Vogdes]

With about a quart of plain old cheapo "Bondo" autobody filler you can experiment with planing wedges. Start out with, say, a 1.5" wide by 5/8" "high" (at the stern edge) wedge, and try it out. Grind it down if it seems like too much, goop on some more if you'd like some more. My guess is that this will be more effective than trim tabs in getting the boat up on a plane. Because the wedge has a longer chord, it maybe doesn't create as much drag as trim tabs?
Once you've established the size and shape you like, you can always grind off all the Bondo and replace it with a hand-fitted wooden wedge, made out of Pundingy wood harvested in the headwaters of the Amazon, and finished with 36 coats of varnish.
Also, you might try what I think are commonly called a "DoelFin," which is a plastic horiztontal fin that bolts to cavitation plate on your outboard. They help the boat get up out of the hole, at the expense of a little bit of top-end speed.

All good stuff... Especially the 36 coats of varnish lol.
I think a little more hp might help, depending on how things are set up 15hp might be a little under powered.

[Garret]

Richard -

Don't skimp! Too small a wire will 1) create a fire hazard & 2) possibly damage the motor. If it's 40 amps (that # seems possibly low) & 10' round trip - your min. size is 4 ga. Find the amperage draw for the motor (talk to the dealer, find a manual online, etc.) & check a sizing chart please (http://www.affordable-solar.com/Lear...ls/wire-sizing). Also remember that any connectors need to be equally large. Even if you can somehow hook up a household plug to 4 ga. 10 min. of runtime will probably have it hot enough to melt it.

Your wire will need to be substantially larger than the 2' wires that come with the motor.

My 2 cents

[Breakaway]

+1^

[wizbang 13]

And of course , assuming you have played with engine trim, and are not turning too big a wheel.

[Rich Jones]

I was given bad advice by a dealer as to the engine size when I bought that 15HP. A little voice in my head was screaming, "Get the 25HP!!", but my wallet was screaming, "Take the cheaper engine!". I've always hated this 15HP Merc 4-stroke (bad carb problems) I have and would LOVE to upgrade to a different brand 25HP. The only problem is sneaking it past my wife....

[PeterSibley]

I was thinking just the same thing. Jumper cables seem awfully big, but I guess they're big for a reason. I'll probably go that route to be on the safe side. It's just a fishing boat, so it doesn't have to be pretty.

Have a good look at the amount of actual wire inside the lead before buying .... some of the cheap stuff has VERY thick plastic insulation and very thin wire .

Welding cable tends to be good quality with known capacity .