I'm about to reinstall my centerboard and am now trying to find a
replacement for the gasket material that was used to seal the well
cap. The old one appears to be made from relatively dense gray foam
strips that were about 1 inch wide, and after compression, about 1/8
inch thick. The people at Boat US, and West Marine don't seem to
know, and both have recommended going to a camp trailer store because
they think the material looks like the strips they say are used
between a pick up side rail and a camper unit installed in the cargo
We use 3/16" Neoprene gaskets that are available for $50 pre-cut
Sealing your centerboard gasket trunk against the intrusion of sea
water under relatively low pressure isn't a tough gasket problem.
I would recommend a relatively soft (say about 20-30 durometer)
neoprene, urethane, butyl rubber, or Viton gasket material in about
1/4" thickness. An industrial rubber supply house will sell you any
of the above by the square foot. You will cut it to final shape with
a Stanley knife.
I don't think I'd trust the foam weather-stripping they put under the
cap on a pick-up truck. That seal only has to seal against
Look in the Yellow Pages under "Plastics-Rods, Tubes, Sheets, Etc.
Supply Centers" for a supplier in your area. The supplier in my
Exotic Rubber & Plastics
10341 Hercules Drive
Freeland, MI 48623
S/V Dynamic Equilibrium