Join Date: Sep 2008
Location: Victoria B.C. Canada
Thanked 111 Times in 102 Posts
Rep Power: 10
I agree it is probably cored - for some bolts if not all. Core is easy to deal with but it does take longer. Here's a link by Maine Sail - a complete how-to for dealing with core and sealing it properly.
Sealing Deck Penetrations to Prevent Core Rot Photo Gallery by Compass Marine at pbase.com
Living aboard in Victoria Harbour