The jack whistle may "peep" or "toot," and it can be heard on nearby vessels and docks, but it's really all about that particular boat.Two "jacks" is for the engineer: fire-up the engines, or come on up to the wheelhouse. One jack let's the deckhand know he's needed on deck to put up a line or take one in. Three jacks means "all finished with engines." And so on.
It seemed like a good name for a new blog about working on tugboats. Seeing how I've stretched this one way beyond crewboats.
Anyway, if you're interested, drop in for a visit.