Starting cables

I am re-routing my main cables (connected to the starter). They are currently running one on each side of a stringer. I am thinking of bundling them together. Any reason these cables should be apart from each other?

If they are seperated by a stringer, they cannot possibly short together. If you bundle them and pull the straps too tight there is a danger of an eventual short circuit. Technically, bundled wires must be derated for current carrying capacity because of heat.

In the real world, as long as you don't pull the tiewraps tight, it shouldn't be a problem. On the other hand, it may be easier to leave them where they are and avoid all risk.

Shorting isn't the issue, heat build-up is, and bundles are usually considered to be 3 or more wires/cables. NEMA codes rate cables by size and insulation material and specify a maximum amperage for "free air" and a lower rating for bundled or enclosed cable. FAA and ABYC requirements are slightly different in their approach, ABYC has different ratings for "in an engine room" and "intermittent use" but they all attempt to provide standards which will prevent melting the insulation which then leads to massive shorts.
If you were to connect a #10 to your starter you'd probably melt the insulation and maybe the wire without turning over the engine, but two #1/0 cables tied together could probably handle simultaneous locked starters for a short period without a problem. Best approach is to use the charts and size and tie the cables as recommended.
Or then again you could consider running one cable to a terminal post and splitting it off to each starter, depending on how your starting banks are arranged. That probably won't work if you like starting both engines simultaneously, but most people don't.

My post was not too clear I think. I have only one engine, I'm talking about the positive and negative. They are size 00 and run for about 8 feet.

Fotoman said:

My post was not too clear I think. I have only one engine, I'm talking about the positive and negative. They are size 00 and run for about 8 feet.

Click to expand...

It was clear to me. I think as long as you don't bundle them with wire ties and pull the ties as tight as you can get them, you'll be fine. I have seen insulation damaged by wire ties that were pulled too tight. This could lead to a short circuit at some point in the future.

Since engine starting cables have no circuit protection other than the internal resistance of the batteries, this could start a fire.

Pull the ties finger tight, no more. Or use insulated clamps to hold the cables.

All the jumper cables I've used are bundled. What's the big deal?

Fotoman said:

My post was not too clear I think. I have only one engine, I'm talking about the positive and negative. They are size 00 and run for about 8 feet.

Click to expand...

There really is no reason why you can't run the cables together if they are in good condition. I had this same issue a while back but chose a different approach. I moved the start battery and placed it right next to the starter. this gave me a very short cable run, which is a good thing, and moved some of the cable away from the side and front of the engine. See our post here,
The Trawler Beach House: Moving The Starting Battery . Chuck
http://trawler-beach-house.blogspot.com/2012/03/moving-starting-battery.html

I did the same as Capn Chuck. Battery beside starter , with on off switch mounted to the stringer. Through same floor panel I use to access fuel tank valves.

Excellent. Thanks guys.

OFB said:

I did the same as Capn Chuck. Battery beside starter , with on off switch mounted to the stringer. Through same floor panel I use to access fuel tank valves.

Click to expand...

Nice profile picture OFB. Hate to see it go down like that.