Re: water intrusion from deck stepped mast. I made a plastic (cheap cutting board) template to locate the wire location under the mast. Use the bolts as an index. Then after removing the mast step casting, I cut an opening around the mast wires at the cabin top. I slid a sleeve of bicycle inner tube over the wires and then a threaded bronze nipple over that. (use the largest one you can make fit) I made gummy ball of thickened epoxy to plug the bottom of the hole I'd carved in the cabin top and then filled in around the threaded part of the nipple with a more wet thicked epoxy mix. The template comes into play locating the nipple so the mast step casting is not interfered with... I have a piece of hose over the wires and onto the nipple. The hose is folded inside the mast so water cannot enter the boat in this area - period! I didn't need the nipple and a thinner stainless tube could work as well - but I had the nipple already...
The following year I addressed the dimple which had been driven into the cabin top by the previously unsupported mast loads. I floated a mast step turning plate on a bed of thickened epoxy (used nylon washers to shim it properly, a dab of five minute epoxy would hold them in place.) The trick there was to make sure the step wound up perpendicular to the where the mast should point... You get one easy chance at this so get those shims glued and mask the area around plate on the cabin top (doing it again, I might use a bead of silicone caulk as a dam to control the epoxy flow.) I've got a dry boat, and with the plate and turning blocks, am taking more loads and leaks off of the cabin top...