This looks pretty good and if you ran it this way it should work! The things i noticed. . . Tank should be grounded to the negative buss...
Xcel spreadsheet for load calculations naupigos, I found this a while ago while looking for an easier way to calculate battery bank...
Bazz I've seen many a circa 1990's twin engine boat with a mess for wiring. The two engines, and corresponding control gauge panels should be...