ATO/ATC fuses have a maximum size of 30 amps.
Fuses are to protect the wire, not the item at the end of it. The exception to this might be low draw electronics that use a smaller fuse. If using 14 awg wire which is pretty normal, 15 amps is appropriate. Thar is why all Blue Seas circuit breaker panels come standard with 15 amp breakers. The maximum rating for the fuse block is 100 amps.
I have no idea where you read 150 amps.
Living aboard in Victoria Harbour