You would have to get into the cfr's to determine that.Off the top of my head. Typically less than 26.5 feet towing vessel does not require a license. Fishing vessel less than 6 passengers is a 6 pack license. Over 6 persons you may need and inspected vessel license. If the boat is not used for commercial purposes no license is required. example if you are the captain on a yacht and taking his family out. Where it get's hard to read is if the vessel owner brings some guests.
Documenting seatime. is a prosecutable felony so just make sure whatever your documenting is valid and you can back it up.