Agree with Dogship that the source of the leak is more likely a stanchion base than the toerail proper.
Access may be an issue, unfortunately.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)