Mast Base

I picked up a new to me mast but the mast base needs to be replaced. My plan is to pull the one of my other mast and put it on the new one. What size/type (aluminum Stainless) rivet is needed and is there anything else I need to do the swap ie. Is there supposed to be a rivet cap on it?

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Division 10, Fleet 185
Hobie 17 and Hobie 14

Aluminum rivets aren't very strong. I don't use them for anything but trim and batten pockets. I'd use a stainless or monel rivet about 3/16 diameter, 3/8 length. By "rivet cap" are you referring to the SS inserts used to make it watertight? If you have some, use them. I just used a sealant. Unless you are turtled or submerged I can't see how much water could get in at the base of the mast. I often wondered why masts don't have a one way drain hole at the bottom for water that is more likely to get in up top when the boat flips.

If I remember correctly, there is a plug about 4 inches above the mast base, so I don't think a rivet cap is required. However, when you have the mast base off, inspect the plug and ensure that the sealant that is there is intact. If not, supplement as necessary. I would also add a bead of silicon around the seam between the mast base and the mast...never hurts