Fuses/Breakers

I have a 2005 Classic and a 2005 Merc 200 EFI 2.5 liter engine. Since my boat/motor are getting older I want to get some extra parts stored in the boat.I have a question regarding fuses I should have for backup in the boatEngine - 20 & 15 amp ATC fusesBoat - 20 amp & 50 amp breakersAm I missing any and are these the correct fuses/breakersAlso what else do you carry as "extra" parts in your boatsThanks