how much water can floatation foam hold?

I am fairly certain that the foam in my 91 stratos 295 PE is soaked. If it is, how much weight could this be adding to my boat? And would most of the weight be located towards the stern?

Several hundred pounds. Contrary to popular belief and most marketing programs, closed cell foam can and will absorb water if used where it can get exposed and no way to dry out. Why do you think yours is full of water?

Is this foam water resistant?

Yes, but with the following caveat. The foam considered closed-cell, which means that each cell that makes up the foam structure is completely closed off from surrounding cells which prevents it from acting like a sponge. It is completely safe for this foam to be in contact with water for hours/days/weeks and even months with no adverse effects. However, it should never be submerged in contact with water permanently. Over a period of years the water contact can begin to soften the foam and cause it to lose its closed-cell status. This foam is designed primarily to be used as an insurance policy in case of damage/holes that could cause a vessel to lose buoyancy. Pinhole sized openings would essentially have no effect on the foam since the amount of exposure is so minimal but you should always make repairs as soon as possible to keep the foam effectiveness as good as possible. This will be the case with all after market closed-cell polyurethane foams and even manufacturer installed foams.


Our 2LB foam is generally used for most marine flotation requirements due to its good flotation properties of approx. 60 lbs of buoyancy per cubic foot. For flotation applications requiring some structural elements such as helping to support your deck or strengthening between stringers or bulkheads we would recommend using our 4LB density foam, which is also appropriate for filling around gas tanks.

I dug the waterlogged foam out of my 1974 ranger. Enough to fill three trash cans of just foam. the suprising part was that I could not lift or move the transh cans when they were full. I imagine each one was about 250 lbs. so about 700lbs total and that was a 16ft boat!

I drilled some holes in the flotation boxes etc, because water was weeping from the fiberglass. once drilled, a fair amount of water came out, so I am guessing the foam is waterlogged. Which only concerns me a little because I hope to pull the top this winter once I get my garage built.

I was wondering how much weight it adds because it seems to sit low at the stern and wondered if the water in foam could cause some of this.

However after reading some of the posts, I would say an extra 400lbs is not unreasonable and it may be more.

Im rebuilding my Astro 20' and i pulled around 800lbs of water logged foam out of my boat. And it fealt like i was pulling a lead sled up and down the road. If you can find a set of scales around your area you could weight it and see how much you pulling.