What I need is some product that I can inject and fill in a section 2'X2'X3/4 were there was once plywood. It is a none structure just a deck section that the wood rotted out of and I want to fill in the void with something way more dense than spray foam for sealing windows as it gets walked on. Hope you know what I am trying to explain. Thanx, Andy...

How about a piece of starboard? If it has support all the way around it should work for you.

use pour foam... its a two part mix and there ar higher densitys.

Have you looked into seacast?

What about marine trex or other similar type of epoxy filler?

here ya go, careful with the lighter densities. They have a pretty big ratio of expansion. They WILL blow right out of the fiberglass if not careful. Best to work in small amounts with a plastic syringe. I have used this to repair cores that are not accessable by any other means and i could not break the outer skin. Works great but like i said be careful it will get away from ya.

http://uscomposites.com/foam.html

Looks like the stuff I need, any left over I will use on my late paying customers bung holes. Everyone wants there boats done yesterday but when payment is due they always say tomorrow. I guess payment will follow after there bowel movements, usually in 2-3 weeks.....too funny...

can you read this ole friend