Proper wire size for relocating trolling motor battery

[Valley Boater]

I have a 16' Starcraft that is rated for 50 hp. The boat is open and tiller steered.

However, I fish almost entirely on electric only lakes and am currently using a 55 lb. Minn Kota V2 on the bow and a Motor Guide 55 lb. on the stern. Occasionally I'll put on a 9.9 outboard to use on a couple of lakes that have a 10 hp max. With both the live well and a 12 v battery near the bow and no heavy outboard on the stern, the boat tends to be too light in the stern. I would like to shift some weight to the rear by mounting three 12 v batteries (1 each for the trolling motors and 1 for the accessories) as far back as I can mount on the floor. I'm planning to run the power to the front motor plug via 8 gauge marine wire for both the positive and negative (a run of approximate 13'). I am also planning to use 8 gauge to energize the fuse panel (approximately 6').

Is 8 gauge wire sufficient for the loads and run I am facing?
If I upgrade to a 24 v bow mount in the future will the 8 gauge still be sufficient?

Thanks in advance for any response.

Don

 

[MH Hawker]

Re: Proper wire size for relocating trolling motor battery

6 ga will hold 75 amps so yes its fine for 12 and 24 volts.

 

[bruceb58]

Re: Proper wire size for relocating trolling motor battery

Depends on how much voltage drop you are willing to tolerate. Use a calculator like this to see what the VD will be
Voltage Drop Calculator Genuinedealz.com

If you switch to a 24V motor and the max current is the same, the VD will be the same.

 

[otto1946]

Re: Proper wire size for relocating trolling motor battery

Depends on how much voltage drop you are willing to tolerate. Use a calculator like this to see what the VD will be
Voltage Drop Calculator Genuinedealz.com

If you switch to a 24V motor and the max current is the same, the VD will be the same.

Hey Bruce pretty awesome tool.

Only real question I have is how do you determine how large of an amp draw you have. Is there a tool for that? I believe my alternator is rated at 70 amps, but that doesn't tell me what my accessories draw.

Ive been looking around and haven't been able to find any information. I have a 2008 Mercruiser 5.0 MPI with a JBL 4 speaker Sirius satellite radio, a Lowrance 522c GPS/depth/fish finder, i am also installing a VHF radio as well as some of the awesome LED lighting such as you and Chriscraft have installed.

I am converting my boat to a 2 battery system, using a Perko switch I am gonna keep them in parallel to keep them at 12 volts. I already purchased a Switch and 2 group size 31 AGM deep cycles, but i'm not sure about the wiring. I plan on running 1 AWG marine grade wiring.

I know from my experience as an aviation electrician you usually want to mount the switch as close to the source as possible, but I want to mount the switch as close to my console as possible so I can control my switch while underway. Unfortunately that will put my switch approximately 20 ft away from the batteries, so it would be nearly a 40 ft run there and back. That is the main reason i had planned on using 1 AWG.

If i use the tool you provided and I just select a 70 amp draw, it says I'll have a 5.94% voltage drop. It also says you don't want more than 3% voltage drop for bilge, lighting, main DC and so on. But if I am only pulling 35 amps then I'll be just inside that window. It is honestly the only reason I haven't installed it yet, and the main reason I found this awesome forum. I've searched the internet as well as this forum, but i'm still not sure.

I'd appreciate any information, thanks.