I'm upgrading to a 105 amp marine single wire alt in the 21 which means I'll need to upgrade the wiring also. The way it's wired now, there's a 10-12 gauge wire from the alt to the block on the back of the engine. From the block it splits to the ignition switch and the starter. On the starter terminal is also the battery cable which provides the charge to the batteries through a Perko switch.
I have a concern about this and what I'm thinking may take care of it and make it simpler. The wire is 10 gauge running from the alt to the block, then to the starter and has got to have some loss (and won't handle 105 amps). It just looks like this was the "easy" way, not the right way. I'm thinking I keep this, but add a 8 gauge wire directly from the alt to the terminal on the starter. This way I still have power to the switch and other circuits as well as a large gauge wire to charge the batteries. The alternative is run 8 gauge to replace the existing circuit.
Make sense, or am I overlooking something?
No reason to keep the wire from the alt to the block, take that out and add the heavier gauge from the alt to the starter lug. That 2nd wire off alt to block just adds more of a chance to chafe a hot lead to ground on the block. Just take it out after you add the thicker shorter wire.
I have 2 minor reasons to keep that section of existing. A little more gauge (more capacity), and that section is in a harness. If it wasn't 100 degrees out I'd dig into the harness.... maybe after summer.