SEALED CELL FOAM ...

Help needed in choosing a sealed cell foam eg two part ? I need a non water absorbing foam.

The foam is to fill the brackets supporting my outboards. The volume will be approximately (5'0" x 2'6" x 9") approximately 9 cubic feet. With seawater at 62lbs/cf, I am hoping for 558lbs of floatation.

Thanks

i am sure that the expanding cell foam that you get from builders merchants is waterproof and fills a big area pr tin,also not to costly.