Some time back someone in the regulatory world decided that all boats below
a certain size should not sink. The manufacturers responded by injecting
expanding foam into various spaces, mostly under the floor but sometimes
also in the sides. The problem is that this meant that these boats no
longer had an open, draining bilge. They thought that water would not get
into these sealed compartments they created for the foam. But water, given
enough time, can get into just about anywhere. Water gets trapped in these
spaces and that results in the foam getting waterlogged and the wood
rotting.

You can buy the foam from www.uscomposites.com where you can also buy epoxy
to reseal your new floor. It will probably last another 25 years or so if
you simply redo it the way it was. Adding a few new compartments will
probably not reduce the floatation enough to sink the boat. I replaced my
floor and outboard stringers and I did not replace the foam. Instead I
drilled drains in my stringers and restored my bilge to an open bilge. I
did that so water could drain and my new floor would not rot. My boat will
sink if it fills with water. But my boat is a small open bow boat that I
use on local lakes where it is not possible to even get more than a few
hundred feet from a shore. I have heard of other solutions such as using
sections of those foam noodles and sealed 1 liter coke bottles to add
floatation without trying to create sealed compartments.

wrote in message
ps.com...
I just bought a 16 foot shallow v hull mirrocraft fishing boat. I
bought it used and planned on replacing some rotted wood, as well as
reconfigure the storage space in it. It now has 3 battery storage
compartments. Two near the outboard (35 hp) and one inside the
casting deck. The battery inside the casting deck is placed right in
the middle which makes it difficult to fit anything other than small
items inside of this storage area. Near the transom of the boat there
is a livewell in the center with a compartment on each side which open
up to two more battery compartments. There is raised decking that
covers the livewell and battery storage areas as well as all of the
space around them. The only openings in the raised decking was for
the livewell and batteries. I took off the decking with plans to
utilize as much storage space as possible but found that all of the
space surrounding these areas was filled with foam. If I remove the
foam I will be able to triple my storage space but I am unsure of its
purpose. I do not want to remove it if it serves a useful purpose.
Any suggestions from anyone with more experience would be greatly
appreciated. Thanks alot