I would add that there is no "Romex" on a boat. Romex is a brand name but generally refers to solid strand NM-B cable for houses. What you see is marine grade tinned stranded duplex or triplex.If I may, and please don't take offense, but from what you've written it sounds like you're new to wiring? "Electronics" don't get shore power... they are 12V items and get their power from the 12V distribution block/breakers/fuses. Your battery charger simply keeps the batteries charged when you're not running the engines. Also, if you are new to doing wiring, your goal of adding a charger means you're now dealing with AC power, not DC... which can be more dangerous. But... that said...
You need to know the power draw of your onboard charger and the new charger and verify that your AC wiring and fuse/breaker can handle the increased load safely. If that's good, you COULD add circuit - but you need to do it properly with a electrical box, clamps and crimp connectors.
Personally, I wouldn't do this since you now have two chargers supplied by the same circuit. If the circuit goes bad... they are both inop. And, you wouldn't have individual control over each.
The best plan... add a new (properly sized) breaker in your AC circuit breaker panel and run a dedicated line for the new charger.
If your boat doesn't have an AC breaker panel then I would consider installing one as they're not overly expensive. This would really be the preferred and cleanest way to do that. It's a bit more money to do it this way (not a whole lot, though), but it's the best way in the long run.
I added the bold and underlineI would add that there is no "Romex" on a boat. Romex is a brand name but generally refers to solid strand NM-B cable for houses. What you see is marine grade tinned stranded duplex or triplex.
NEVER use solid wire on a boat.
When I say distribution I meant breaker panel. I can wire a house but someone just closed their eyes and wired this boat. I have a 2 bank charger currently hard wired into the area under the battery compartmen. I just wasn’t sure if there was a sub panel of sorts in the battery compartment or if all of the wiring runs all the way to the back of the boat to individual breakers. I have a 2 bank (10 amp total) charger hard wired but want to have another 3amp x 3 Noco added to shore power. I doubt the total draw would hit 19 amps at the same time.If I may, and please don't take offense, but from what you've written it sounds like you're new to wiring? "Electronics" don't get shore power... they are 12V items and get their power from the 12V distribution block/breakers/fuses. Your battery charger simply keeps the batteries charged when you're not running the engines. Also, if you are new to doing wiring, your goal of adding a charger means you're now dealing with AC power, not DC... which can be more dangerous. But... that said...
You need to know the power draw of your onboard charger and the new charger and verify that your AC wiring and fuse/breaker can handle the increased load safely. If that's good, you COULD add circuit - but you need to do it properly with a electrical box, clamps and crimp connectors.
Personally, I wouldn't do this since you now have two chargers supplied by the same circuit. If the circuit goes bad... they are both inop. And, you wouldn't have individual control over each.
The best plan... add a new (properly sized) breaker in your AC circuit breaker panel and run a dedicated line for the new charger.
If your boat doesn't have an AC breaker panel then I would consider installing one as they're not overly expensive. This would really be the preferred and cleanest way to do that. It's a bit more money to do it this way (not a whole lot, though), but it's the best way in the long run.
OK, good, that helps. If you didn't see it, take note to the reference about boat "romex"I can wire a house