Enough of something to fill a boat, or a boat filled with the thing in question
The city consumes boatfuls of fish every day.
2007, January 1, “Amy Cortese”, in At Sea With a Book to Read, and the Author of It, Too:
Often sponsored by publishers, the cruises, aboard commercial liners, feature popular authors who give readings and seminars -- even knitting lessons -- to boatfuls of book lovers.