Mac 25 Deck core and chainplates

jbrock

.
Jul 12, 2009
54
Macgregor 25 Regent Point Marina, Virginia
I’m going to just expose my ignorance here. Does the Mac 25 have a deck core that can potentially rot from water penetration? There appears to only be gel coat and fiberglass without a wood core. My chainplates are leaking and need to be resealed. They are riveted on. I was going to remove them, clean everything up, use butyl tape to seal, then place new rivets. Should I also push some epoxy into the holes? I would think that’s only necessary if there is deck core to be concerned about. Any suggestions? Thanks guys.
FD4B9BFD-F754-4A56-9AA7-F1EC58FE93CD.jpeg
 
Sep 25, 2008
957
Macgregor & Island Packet VENTURE 25 & IP-38 NORTH EAST, MD
there is no core in the chain plate area (core plywood is under the blue non skid areas ). drill out those rivets, clean out the old caulking, and reseal with Lifecaulk or 4200. Use #10 machine screws, with nuts/washers underneath, to hold the plate down. These new to be recaulked every couple of years.
 

jbrock

.
Jul 12, 2009
54
Macgregor 25 Regent Point Marina, Virginia
So don’t replace with new rivets instead? How do I put the nuts/washers underneath? All I see below deck is the vertical chain plate on the sides of the cabin.
 
Sep 25, 2008
957
Macgregor & Island Packet VENTURE 25 & IP-38 NORTH EAST, MD
it just occurred to me that you have a newer 25 than mine, which doesn't have the flat side decks that mine does. See if you drill the rivet hole all the way through that you can get to the hole to put a nut on the screw. It may be hidden by the hull/deck trim piece.
I bought an extra set of the cover plates and used one below as a big washer (to hold more sealant). This is the best picture I could find of my chainplate in the interior.
v25chainplate.jpg
 
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srimes

.
Jun 9, 2020
211
Macgregor 26D Brookings
So don’t replace with new rivets instead? How do I put the nuts/washers underneath? All I see below deck is the vertical chain plate on the sides of the cabin.
I did mine (26D) with rivets and bed-it butyl tape. A pleasure to work with vs 4200.
 
Sep 25, 2008
957
Macgregor & Island Packet VENTURE 25 & IP-38 NORTH EAST, MD
Out of curiosity, do these boats have an inner liner in the area around the chainplate?
in my picture above, the yellow is the deck piece, the white is the interior liner, which goes from the hull/deck joint on one side to the joint on the other side. The 3 bolts in the chain plate go through the liner and the hull.