Yankee Marine Services has 4 mooring balls and occasionally a 55' dock space available for transient use. The four moorings are top tier quality, with brand new bridles. Below are the coordinates/descriptions for the 3 moorings in the outer-harbor, and the general inner harbor mooring description, as well.
I highly recommend Yankee Marine if you are stopping into Gloucester! We went up for the Schooner Festival over Labor Day Weekend and it was perfect. Not only did they confirm the reservation right away, but they were extremely accommodating for our two boats, allowing us to raft up instead of staying on the moorings in the outer harbor. There is a public dock right night to the pier so using the Harbormaster Launch service was very convenient for getting around town for the weekend. In addition, the Cripple Cove location was sheltered and it was a nice and quiet spot to stay. There is a little breakfast place across the street that we could walk to and all of the other boat owners were very friendly and helpful with suggestions on where to go for dinner, live music, etc. The only downfall (nothing major for us) was that there is no shower facilities, but we knew that when we made the reservation, and we had no problem with that. The owner was very quick to respond to texts and calls on the phone. If you are interested in checking out Gloucester for a night or a weekend, I would highly recommend this location. We will definitely be back again.