Is butyl rubber caulk O.K.

[Diesel Bill]

Originally Posted by Lancerbye

Having the same boat, I know exactly what the problem is. The deck stepped mast sits on a plate that has a raised center and a triangular hole with an extension that goes through the deck providing wire access. The water comes through the inside following the wires and ending up following the compression post down. This had happened to my boat and rotted out the bottom of the compression post. Remove the teak veneer that is covering the compression post. Do you have access to the hole that comes through. Mine had an a/c unit in the space above the hanging locker. I removed that when I first got the boat. There is a cut out in the compression post that is accessible through that compartment. Use expanding foam to seal the wire through way, from the bottom making sure it surrounded every wire. No more water leaking.

I still have the air con above the hanging locker. I'm reluctant to remove it as it kept me alive while in La Paz, Mex. I might still need it in the future. I plan on removing the passageway panel abutting the compression post as it's water damaged now. Can I access the cut out on the post you mentioned from the passageway side? What about sealing from inside the base of the mast through the round access cover? Looks like I've got another project for the next week or two. Hope I caught this soon enough so as not to have to pull the mast. Was hoping to get some local sailing in this summer as I save up funds for new running and standing rigging. I re rigged my old 27 foot ketch myself as it had tabernacle stepped masts. I lowered them down to the deck and measured shrouds and stays and ordered what I needed and reinstalled it all and raised them back up. This appears to be a much bigger job. So anyway it is what it is and will get done as money and time permits.
Thanks again for all of you who have added to my knowledge.

[Diesel Bill]

Well I made it to the boat for a few days and got into the base of the mast for a look see.
I think I lucked out big time. The water leaking in through the wire run was a recent occurrence and was caused by the drain at the back of the mast step being plugged with dirt/crud. The bolts and washers holding the mast step were in good condition as was the metal step. After cleaning and vacuuming the dirt out, I pumped some butyl sealant around the wires where they penetrate the mast step and used my hand with disposable glove to squish it into the gaps between the wires and down into the wire penetration. Found a bad section of wire insulation on the anchor light wiring and cropped that out. Unfortunately I can't post the pictures but I'm happy.
Also checked the compression post down at the bottom and found no sign of rot.
Thanks to everyone for the encouragement.

[Tayana42]

Sounds like good news. Hope all your boat projects go so well.

[Pete O Static]

It was previously mentioned that your core will likely be getting wet. Good advice. However, it is unlikely that the area of the deck between the mast step and the compression post is actually cored. If it is, it would be with something quite substantial. A balsa core could not withstand the compression loads.

Another trick that works well for sealing wire runs from your mast is to use a $2 wax toilet seal. Take some of the wax and fill the hole around your wires with it. My mast is keel stepped and I seal the gap around the shims at the partners using a toilet seal. Keeps everything dry as a bone.