At the beginning of an underway I log date/time, engine hours, generator hours, who is on board, destination, general weather conditons, sail configuration, any fuel added and anything special that I feel like logging (like spotted sea turtle off Haig Pt, etc.) When I get back in I log date/time, engine hours, and generator hours. I use the same log for maintenance and repair items as well as oil changes, filter replacemnts, zinc replacement, fueling gals, pump outs parts repair or replacement and any major improvements (like adding tank level indicator) if any, etc. That way I have it all together. I have a Weems & Plath log but any bound notebook (not loose leaf) would be fine.