Otter
Well-Known Member
Right, that fuse is almost certainly too high. If you run 100 Amps on your domestic side, you either have a super yacht or a cruise liner. I wager there is no way will you run 100 Amps even with every bit on domestic demand running. I would seriously reduce this fuse probably to somewhere 30 Amps (but I do not know your equipment loadings). A 100 Amp fuse will be too late, you will see acrid smoke before that fuse blows as the fuse amperage will state the continuous rating not the blow rating!
OK, again, this 600 Amp fuse is also well over rated, far, far too high!. A 600 Amp fuse will have a blow rating at somewhere up near 1200 Amps.
The cable from Engine battery to Starter motor is probably rated at 400 to 500 Amps maximum continuous and will start to get hot, go soft and melt long before that fuse will blow!
I suspect your starter motor has a cranking current of somewhere near 200 to 300 Amp and this starter motor current is intermittent not continuous so this fuse can also be possibly reduced to 150 Amp but you will need to check the starter motor current.
Nigel Calder recommended a mega fuse BUT he certainly did not mention 600 Amp?
The autopilot alone has a 40amp fuse so a 30amp fuse overall would be a bit silly. The 100amp battery fuse is to protect the main heavy duty wiring from the 440amp battery bank, it then splits into two switch panels each circuit of which has its own much lower fuse/breaker so the 100amp is fine. The engine is a 75hp beast with a high CCA demand, the fuse is to protect the wiring from a catastrophic short and the fuse on the bow thruster is the same for the same reason.