Without the weight of the boom pushing the lower bracket against the mast, I was able to see that the bracket was very poorly secured. The port side rivets failed completly and the starboard were loose. Video link -
Attached image after I drilled off the heads of the rivets revealing how the rigger had mounted the gooseneck to the stern side of the mast.
This is a ZSPAR mast. The rivet needs to span about 5/8ths on the port side to get purchase on the back of the channel (which is visible in the attached image).
I tapped the mast on the port with 1/4" X 20 thread and the starboard with 5/16" X 18. On the starboard th 1/4 inch holes were worn out of round and could not be tapped 1/4th inch. I bought some stainless hex drive flat head screws. Diameter of the head on 5/16" kinda gets in the way, so prefer to keep the 1/4" on the port side. Upper and lower gooseneck brackets both have cups that the toggles sets in with a bushing. Bushings are no longer made so I bought something in nylon close to size from the hardware store.
Will it hold? Easy enough to check through the season and if it loosens, I will try a dab of Loctite.
I tapped the mast on the port with 1/4" X 20 thread and the starboard with 5/16" X 18. On the starboard th 1/4 inch holes were worn out of round and could not be tapped 1/4th inch. I bought some stainless hex drive flat head screws. Diameter of the head on 5/16" kinda gets in the way, so prefer to keep the 1/4" on the port side. Upper and lower gooseneck brackets both have cups that the toggles sets in with a bushing. Bushings are no longer made so I bought something in nylon close to size from the hardware store.
Will it hold? Easy enough to check through the season and if it loosens, I will try a dab of Loctite.