Coming back from a short trip last weekend I noticed a bang-bang from the area of the shaft at low speeds. I was worried I had snagged a crab pot and had a remnant part rotating around the prop. A diver checked on it and found nothing but the sound persisted.
I made a call (on a Saturday) to one of my favorite service shops, Haven Harbour. Service Manager, Greta Sommers talked to me in the phone about it. That conversation was helpful deciding to get the boat towed to a nearby travel lift today. As it turned out Jabin's was willing to work with me (on a Saturday) and TowBoatUS arrived very quickly and was free, thanks to my BoatUS membership.
So, the bang-bang when in gear was from the shaft zinc which had come loose and slid forward to bang on the strut. The travelift team at Jabin's spotted it right away and were pretty sure that was the issue. A quick trip to West Marine while the boat hung in the lift and bingo, I was ready to go back in the water, problem solved.