Another AWG Wire size question - need help for complete re-wire project

Hi Everyone - Ihave read lots of past threads on this issue (there is a lot of info out there) but I'm still alittle confused / intimidated by this project.

I have a late 1970's Glastron 20' inboard with a Mercruiser 165.

I recently got a new re-built engine and the only thing keeping me from putting it in and gettin ont he water is the complete re-wire job ahead of me.

I have replaced all the guages in the dash, and realized while I was doing this that the previous owner had butchered a re-wire job replacing with poor quality materials.

I need to re-wire from bow to stern, but have got some concerns surrounding AWG wire guage selection.

If I run a power lead from the battery in the stern to a fuse panel / bus bar in the helm (aprox 30' round trip if I over estimate) would a 10 guage AWG wire be sufficient?

Then from the fuse panel to each switch / accessories if I went with 14 guage (using 16 guage for the panel guages) would I be safe?

I also need to run dash to engine wires (tachometer, oil pressure, temp, etc.) could I get away with 1 specific guage for all - perhaps again the 14 guage?

Thanks for your help in advance - any other reading or reference material on the subject you can reccomend would also be appreciated!

Mike

Re: Another AWG Wire size question - need help for complete re-wire project

Welcome to iboats!

For a little headroom, go with 8 gauge for the feeds to the fuse block and negative buss. For pretty much everything else (gauges, lights, fishfinder, VHF radio, etc.), 16 gauge is sufficient. A high-power stereo would be the exception.

Re: Another AWG Wire size question - need help for complete re-wire project

NYbo'd advice is good. You should check out Genuine Dealz for the wiring as they have good prices on "tinned marine" wire and all the odd colors you'll need, pink, brown etc.

What shape is the original fuse panel and are you replacing it? I installed a Blue Seas fuse panel and it worked great since it has an integrated ground buss.

You should invest in a good set of crimping pliers if you are doing a complete re-wire, A $10 crimper from Home Depot isn't going to cut it. There is a difference in crimps too, spend the money and get good crimp terminals(Genuine Deals). I use adhesive lined heatshrink tubing on my battery cables, because I used non-tinned welding cable. But for everything else I used Liquid Tape with normal heatshrink. Liquid Tape is kind of a PITA since it has to dry, but it goes a long way and does a good job of waterproofing the crimp-wire connection.

Oh yeah, Blue Seas has a DC wiring calculator, so you can select the correct gauge of wire for your wire runs.

One last thing, a separate ground buss back by the engine might come in useful. I have my bilge pumps, blower, stern light, stern fish finder, fishing light, etc. all grounded at the stern ground buss bar. 5-6 less ground wires going from the stern to helm...

Re: Another AWG Wire size question - need help for complete re-wire project

The vast majority of accessories on a boat are quite low current draw devices so as suggested 16 gauge wire is very adequate. If you try to use heavier 14 gauge wire for instruments and switches you will likely have bend radius issues (marking sharp bends) and neat bundles. Don't even start wiring until you've drawn a complete bow to stern wiring diagram otherwise you end up with a jumbled mess no better than you started with. Check this forum (use the search feature) for wiring diagrams as well as check those in the stickies at the top of this forum (not the top of this page.)

Re: Another AWG Wire size question - need help for complete re-wire project

Make sure the 10 or 8 Gauge wire that runs to the fuse panel in the bow is fused at the battery.

Re: Another AWG Wire size question - need help for complete re-wire project

Hi all, I'd consider a few things before deciding on awg. Such as:

- Length of each run
- total max amperage needed of item or items for that run
- total max amperage needed for all runs from helm
- total max amperage needed at stern to helm based on above + free run for later additions
- Length of stern run (from batt direct to items eg trolling mtr...)
- total max amperage needed of stern items for that run direct from Batt

Use one of many awg online marine awg/fuse calculators that base total max current and total length of run to determine correct awg and fuse size needed.
Good luck.

Typical fusing sizes:
30 Amp - #10 Wire
20 Amp - #12 Wire
15 Amp - #14 Wire
10 Amp - #16 Wire

Re: Another AWG Wire size question - need help for complete re-wire project

Thanks for all the helpfull advise folks - I think I am starting to figure this stuff out....

If I run from the battery to say a fuse panel such as http://bluesea.com/category/81/21/productline/126 then from fuse panel to switch and or accessories / items, then I don't need a buss bar - correct? - however if I run from battery to buss bar to fuse to switch / accessories then I would not need a fuse "panel" - which is I believe how the previous owner set up the wiring on this boat (although his "buss bar" was just a pair of bolts marked positive and negative in the fiberglass wall under the dash).... does this sound like I am on the right track - especially if I am upgrading to the fuse panel shown in the link?

Re: Another AWG Wire size question - need help for complete re-wire project

No need for a positive bus bar under the dash. Just get a fusepanel like the bluesea. You would still want a negative busbar if that is not already included with the fuse panel.

Re: Another AWG Wire size question - need help for complete re-wire project

You would still want a negative busbar if that is not already included with the fuse panel.

Click to expand...

It is the top section of that fuse panel.

Re: Another AWG Wire size question - need help for complete re-wire project

Ok... you guys are just way to helpfull to not keep asking questions..... between the battery and the helm (fuse panel / ignition switch etc.) I assume I should put a fuse or breaker, would it be a good idea to install a shut off or master power switch in between as well?
I'm not sure if it is possible, but I would like to go 2 pos. wires off the battery only - one to the starter, and one to the helm - I will have a battery switch between the battery and starter - just need to know if I should have something between the battery and helm?
Does anyone have a wiring plan they have drawn up that they would like to share as an example?

Re: Another AWG Wire size question - need help for complete re-wire project

The wiring to the fuse panel needs a circuit breaker or fuse near the battery sized for the wiring.
This is for the accessories, and has nothing to do with the engine and ignition switch. That is all on a separate circuit.

Come off the common terminal of your battery switch to the fuse panel, and to the engine. Then when you shut the battery switch off, everything is off.
Something like this. The fuse or circuit breaker (your choice) should be near the battery switch. Size of fuse depends on size of wiring.

Re: Another AWG Wire size question - need help for complete re-wire project

Just curious. Why does the fuse on the hot line leading to the fuse panel need to be near the battery? Why can't it be at the other end of the line, close to the fuse panel? Is it in case there is a direct short in the hot line? (not an electrican)

Re: Another AWG Wire size question - need help for complete re-wire project

It's protecting the wire going forward, not the device it goes to. That way, if the wiring going up to the panel gets shorted, they don't burn up all the wiring. Like the main breaker going to your circuit breakers in your house wiring.

Re: Another AWG Wire size question - need help for complete re-wire project

Don S said:

It's protecting the wire going forward, not the device it goes to. That way, if the wiring going up to the panel gets shorted, they don't burn up all the wiring. Like the main breaker going to your circuit breakers in your house wiring.

Click to expand...

Duhhh! Yeah, now it makes sense OK, just another project to add to my list.