I had to reseal several this November as they were leaking. Between the main flat washer and the nut is a sping washer.
What I found was: there was no sealant under the base except for the edges of the drilled through hull hole. Also this hole is close to the hull side making the flat washer lie at an angle - bending when the nut is tightened.
What I did was - clear out old sealant in drilled hole and thread of base, apply much sikaflex down the drill hole and into socket ın the toe rail (Temporarily plugged underneath) before inserting the s base I placed 2 O rings into the mastic (one the size of the thread the other almost the size of the base diameter so that there was a layer mastic retained between the base and the fiberglass. When you insert th s base into the socket - not much thread will extend into the hull - you have to pull it down as its tightened. Also you may need to change the flat washer for a smaller one or cut one side so that it sits flat. Finally before fully tightening make sure the holes in the base align with the stanchion.Think about guardrail wires. Its a messy job easier with 2 people.
