Re: 1985 starcraft ss
That's a good thought on two wires however, You have to include your anchor light wiring ........ so 4 wires and your control wires too.
I found that my local Interstate Battery shop was a great place to buy marine grade tinned wire at a great price.
My starcraft has the wires for the lights running fore and aft and I mounted my horn right under the bow so there are two wires for that.
My only advice...... DO NOT use any part of the hull as a ground. Everything get's a + and - wire.
If you go the whole way......use marine switches too. I cheaped out and did not on one boat and they lasted a single season! I ended up replacing them with marine switches which I got here on iboats