Originally Posted by Waltthesalt
Looks like you've gotten great advice. One more piece. While ABYC addresses overcurrent protection rarely if ever is the starting power to the engine fused. The reason is that for engines, especially diesels, the starting current surge will likely exceed fues capacity.
This is just not true. There are lots and lots of boats that have both banks fused. The ABYC allows an "exception" for starting circuits IF other criteria are met. It is still wise to fuse the start bank especially on small AUX diesel engines that draw soooo little current. I have been starting on fused circuits for over 20 years. Even had my old Cummins on our Downeast style boat fused. Never in 20 years have I blown a bank fuse unless I shorted the wire or fuse with a wrench. This is thousands and thousands of starts on small and fairly large diesels (Cummins)
In-rush can largely be ignored as the duration is far to short, less than 0.20 seconds, to pop an ANL, Class T or MRBF...
I have well over 40 boats I know off off the top of my head that have engine starting circuits fused. I don't know a single one who's blown a fuse in a "nuisance" blow. I do have customers who have shorted them with wrenches while working on things and popped them but not a properly sized fuse.. Most of these are fused at 300A or less and are sailboats.
I do however know of many boats that have burned to the waterline due to electrical fires because there was not adequate OCP. I also know of at least one Sabre that is still floating because it had the starting circuit fused (see pic below).
The wording for this exemption is one area where I strongly disagree with the ABYC. Even Ed S, the ABYC education director, would like to see the wording changed and the "exception" be only for engines that can't be adequately fuse protected or where the cost would be prohibitive.
These are just some of the reasons I fuse...
Starter wire that WAS fused. This one saved a Sabre from burning to the waterline......:
Starter wire that was not fused (just two minutes before this fire erupted there were a number of 8 & 9 year old junior sailors on this boat):
No fusing on the battery cables, deemed electrical fire:
It is important to remember that the ABYC does not say to NOT fuse starting circuits, they give an "exemption" IF the "starting circuit" wires are protected.