to fuse or not to fuse

I'm nearing completion on a project 12 ft aluminium v-hull,i have a bow mount trolling motor and a fish finder set up on the front along with a battery meter ,my battery is also up front but i was wondering with all the talk on this forum about fuses and breaker set ups ........do i need theses or any protection since i connect directly to the battery

Re: to fuse or not to fuse

Don't take this the wrong way but my quick reaction: Are you kidding!!!!

What if you have a problem with a wire shorting out, or with the motor, or the motor locks up? Stand back and jump overboard before it goes up in flames.

The fuse is absolutely needed, no question.

Re: to fuse or not to fuse

jlinder said:

Don't take this the wrong way but my quick reaction: Are you kidding!!!!

What if you have a problem with a wire shorting out, or with the motor, or the motor locks up? Stand back and jump overboard before it goes up in flames.

The fuse is absolutely needed, no question.

Click to expand...

i don't take anything the wrong way for wanting to know,its all good.where would i put the fuse.... inline or at a box and i assume 1 fuses for each on different things right? also is there a way of know what size fuse to use?another thing is the bigger gauge wire always better or should those be matched to size also........thankz

Re: to fuse or not to fuse

The basic concept is that the fuse is no larger than the current carrying capacity of the circuit it protects.

Start with the motor. What is it rated for? If this is a new motor you probably have a manual that will tell you what to fuse the motor for. If not try to do some research.

If you have that you can determine the size of the wire you need to run to the motor from the battery. There are 2 factors to determine minimum wire size. It needs to be big enough to keep from overheating and burning up, and you want to keep the voltage drop below certian levels. (Voltage drop is the voltage you lose in the wires).

A rule of thumb for current capacity is that 12 ga. will carry 20 amps and 14 ga will carry 15 amps. You then double the current for every 4 gauge sizes you go lower and halve it for every 4 gauges you go higher. So if 12 ga will carry 20 amps, 8 ga will carry 40 amps, 4 ga wil carry 80 amps, etc.

Voltage drop becomes a factor with long cable runs. With high current and long runs you can start with 12 volts at the battery but only have 9-10 volts at the motor. This causes the motor to bog down, draw more current, heat up, etc. Think of what happens to your lights when the house air conditioner starts up.

It sounds like you are close to the battery so this is probably not a factor.

Not sure of your setup but I would look to having one heavy cable to the motor with a fuse close to the battery - about 6-8 inches.

Then put another wire with another fuse close to the battery to power the other gear you have.

Hope that helps.

Re: to fuse or not to fuse

Install a circuit breaker of 40, 50, 60 amps depending on what your motor manual specifies. 6 or 8 gauge wire depending on the motor size. The owners manual for the locator will tell you what size fuse you need for that. All fuses and circuit breakers are installed as close to the Positive terminal of the battery as you can get. Circuit breakers connect directly to the battery.

Re: to fuse or not to fuse

Adding a fuse /breaker to each individual load is the right way to do it.
That said, I've always fused my fishfinders, lights, pumps etc but have never fused a trolling motor. ( Most likely because I've grown up with small-mid sized transom mount trolling motors that clamp rigth to the battery.)

Re: to fuse or not to fuse

ya- I've done it too but you start to think a little differently when you let the factory smoke out of the trolling motor switch/head Circuit breaker or fuse, just do it.

Re: to fuse or not to fuse

well in that case what size fuse should i use for my motorguide 743 43 lbs? i don't have a manual or anything that has that info on it..and for the battery meter and fish finder what the average size fuse used for those.i may as well do it right but note that everything gets unplugged after every trip in order to charge the battery and the furthest away from the TM and meter and FF to the battery is about a foot at most....i can do inline fuses but when it comes to breaker panels and switches well that's a different ball game for me

Re: to fuse or not to fuse

MotorGuide Manuals Online might have what you need to find out. 42 lbs thrust would probably need at least 25 amps? I dunno- Their generic manual states a 50amp breaker within 72" of the battery and 6 gage wire.

Re: to fuse or not to fuse

thankz mark, the model i have i did not see in that listing,weird cause when i made this search that page didn't come up..............anyways i checked all of the mg and they were all 50 amps .thankz for the help everyone