I also have a T-37 with a keel
stepped mast and over the years have experienced leaks. Initially when putting on a new boot it does fine, but as time goes by leaks develop. I've used canvas
, mast boot tape and even considered cutting up my old wetsuit to try to remedy the situation. Two years ago I used the universal mast boot and it seems to be holding up fine. I'll be at the boat this next week and see if any leaks are present. The main thing is to make sure you get a good seal along the top of the boot with a proper caulking. I also did not buy a new giant hose clamp and just used some cable ties around the top and bottom of the boot. UV will affect the ties and replacement will be necessary with time.
The spartite is not meant to be watertight and I did not go that route
. It is a good product and helped a neighbor to put spartite on his boat a few years ago. The advantage of the spartite over other products is that it can stay in place when the mast is removed. When I remove the mast the caulking that I put around the mast partners will have to be removed and reapplied. If I was removing the mast routinely I would go with the spartite, but spending over a hundred on that product vs a tube of good caulking seems like the cheaper route
is better. Good Luck.