I like this
chart from Blue Sea Systems. Warning it is a large PDF but it has fuses, wires and fuse holders all in one place.
For sizing you need to know the current flow in amps. You said you were thinking about going 4-stroke, so I looked at this
Honda at Defender. That has a 12 Amp alternator and on a quick look I didn't see what the current was for the starter but they have a 20 amp fuse in that line so it's less than 20 amp and we can use that for an example.
You said the one-way distance was 17 feet. You base wire size on round trip so you are dealing with 34 feet. Always round up so we are looking at the 40 foot line on the chart.
This would be a critical system and you would not want more than 3% voltage drop.
So you are looking at 6 American wire gauge (AWG) wire for this run.
Next you need to go down to select the fuse size. You fuse based on the wire, not the current. A 6 AWG wire is fused at 125 amps for a single wire with an MRBF terminal fuse (I would think that would be easiest but your overall setup would dictate what type of fuse) or 80 amps for a bundled wire. I would presume this would be a bundled wire but that depends on your setup again.
And the fuse should be located within 7 inches of the battery (at least that is the requirement on an inboard, I don't think it would be different on an outboard).
I know Genuinedealz was mentioned. I purchased some supplies from them and wasn't very happy with the quality. I would stick with some decent tinned wire. Check out the
store here at SBO.
Hope this helped. And I am sure Maine Sail will correct me if I said anything wrong.
Good luck and fair winds,
Jesse
s/v Smitty
