So this is what you are looking for, the trailer connector. Once you find them, there are most often two in there, CUT THEM OUT!!! Replace them with a buss bar and ring terminals or butt splices. These connectors can start fires! They are not designed to have 50+ amps running through them let alone the alt upgrades to 75+ amps I have seen still running though this grossly under designed circuit. This one is clearly melted as you see in the next few photos.


On one boat the engine had been upgraded to the optional 72A alternator and was still running through this circuit. Ouch!! For charging batteries you want minimal voltage drop between the alternator output and the battery bank. For example a stock alternator with a 14.2V set point at 3% voltage drop would have the battery bank seeing about 13.8V. This type of volt drop can chronically undercharge your bank and can lead to premature sulfation and early battery bank death.


This particular boat had 22' of orange and red 10GA wire before it hit the battery switch. Even if we figure the 72A alt will never put out 72A, unless cold, and we base our calculation on just a 60A output, at a 3% volt drop this would require 4GA wire, NOT 10GA. If you want a 2% voltage drop you'd need 2GA wire and this is a far cry from 22' of 10GA wire.....