Engine hours on every line
The date tells you when. The engine hours tell you how much the engine has worked since. Service intervals are set in hours or months, whichever comes first, so a line without hours only answers half the question. Note the hours when the log starts, too, so the record holds up for the next owner.
Keep the paper behind it
A log written by the owner is only as good as the evidence behind it. Keep invoices, parts receipts and service certificates in a file with the log, in the same order. A surveyor or buyer can then match each line to a document.
What a surveyor does with it
On a pre-purchase survey, the surveyor reads the log against the boat. An impeller with no service record is treated as due. A dripless shaft seal without its scheduled service gets a note. Anodes that wasted fast between haul-outs point to a stray current problem. The log turns guesses into facts, and that changes what goes in the report.
When you're the surveyor, say what the owner tells you as you go. Axsail turns what you say on board into the report, so "impeller changed last spring, receipt in the file" lands next to your finding on the pump.