When installing ports, you will cut all the way through the fiberglass sandwich. You should be able to see inside your hull. Do not use the spray foam. You must use some type of epoxy or "git rot".
http://www.boatersworld.com/webapp/wcs/ ... ogId=10051
The foam is not a good adhesive and does not penetrate deep into the fibers of the foam and fiberglass. Spray foam will not solve your problem and may make things worse, when you later try and fix it using the correct method.
Good luck,
Danny Galeana
http://pirates.dwebz.net