Re: Moving batteries, What gauge cable to use?
I've recently done this, so I'll comment on my experiences.
1) You'll have trouble getting an accurate amp draw for your starter. Partially, because the weaker the battery, the higher the amp draw. This really only comes into play if you do NOT have a dedicated start battery. (It sounds like you do). But for boats that don't (that have only one battery) their amp draw will vary significantly, depending on how discharged the battery becomes. A clamp-on amp meter will tell you how many amps you're pulling when you have a fully charged battery.
2) If you put them in the cabin you either need to put them in a sealed space, vented to the outside, or use gell batteries that do not vent hydrogen gas into a confined space. USCG regs spell it all out.
3) There are charts on-line (ABYC) that calculate the wire size needed for marine applications (but you still need to know your total amps). Remember the wire length is always the length TO the battery PLUS the length BACK to ground (essentially, it doubles). Here is one I just Googled:
http://sailboatstuff.com/images/Imtra_Wiring Recommendations.pdf
My outboard used 1 gage from the factory, so when I moved my batteries (~20') I upped it one size and installed 1/0, as suggested above. Overkill? Probably, but I don't ever worry about it cranking.
I bought all my wire and end connectors, etc. from greg's marine wire, just because they were recommended on this site. I was pleased with their service (I bought a lot of little things, in a bunch of different gauges and lengths; and my order was correct/complete).
Todd
