does anyone know a supplier for an off-the-shelf mast collar/coat to fit where mast passes through deck?

Hello Redshank
Not sure which boat you have , but we used Rubbaweld Mast boot successfully on Muffin (P31)

Jan
325/32

newly acquired p31. thanks for info
david

Hello Redshank , in that case congratulations. And another hint.
We found that water coming the inside of the mast was a nuisance, in fact it meant the boat was rarely dry . We cured this by creating a plug of polyurethane(builder's) foam in the mast up to the level of the lowest halyard exit.First make sure all your wiring is OK because to add more you will need to make holes in the plug, then insert a party balloon into the mast at the wiring exit just below the deck and blow it up. This then acts as a base for the foam. Then spray a little water around into the lowest halyard opening and squirt in the expanding foam. Be careful not to glue the halyards up the the side of the mast and also do not overfill. Now you should have a nice dry boat, we did.

Jan
325/32

I have found at my local chandler a product called 'mast collar' made by psp marine tapes. this tape is 100mm x 1.5m, self bonding and waterproof. made for the job! I will fit it when next on board.