Hi,
I'm pretty sure the M376 is one where the chainplates themselves are bolted to marine ply part bulkheads which are tabbed to the hull behind the cupboards in the saloon.
I agree that the problem arises through leakage past the little plates screwed to the deck around the chainplate penetrations, but I have never heard of it causing any problem with the chainplates themselves, The failures that have been recorded are of the marine ply part bulkheads which, after prolonged exposure to water go soggy and rotten, allowing the bolts to pull through them. The leakage can also get into the deck around the penetration, weakening that at the point the top of th part bulkhead bears on it YN severe cases of failure, thepart bulkhed breaks across a line of bolt holes and the top part starts trying to escape through the deck
In my view, the things to look at are:
- The integrity of the sealant around the sealing plate. In fact, don't just look at them, lift them, dig out the old sealant, chamfer the edges of the slot in the deck and rebed them with a modern sealant which will remain flexible such as butyl rubber, making sure the chainplate is sealed to the penetration - not just the plate sealed to the deck, The most common leak path is down the chainplate itself, not betwen the sealing plate and the deck. This job is much easier with the shroud removed from the chainplate, so is good to do when the mast is down, It is wise to repeat every 10 years.
- The part bulkheads which are hidden behind the saloon cabinetry - your mainly looking for signs of water ingress and the condition of the wood and whether the tabbing to the hull remains in good order. Some folk manage to inspect with an endoscope wriggled intothe space, others cut inspection holes made good with dinghy hatches on our M425, the chainplates (3 each side) are all behind cupboards or bookshelves, so we've cut inspection holes which we have covered with offcuts from a teak deck job, held in place with screws. The radical approach is to remove the cabinetry and, if you find a problem, you will have to do that to make an effective repair.
- While you're in there, by all means take a look at the state of the chainplates and their bolts, but they are most unlikely to show any sign of distress.
Peter.
