In the case of my boat, a weldcraft, I took it out one day fishing and I had a friend of mine in the boat who was rather heavy set, but I noticed a substantial loss in top end speed and I noticed the boat took longer to get up on step, and I also had noticed I was burning more fuel than normal.
I decided to give my friend the benefit of the doubt and pull my floorboards, in my case, I had waterlogged foam.
The foam itself is a closed cell expanding 2 part mixed foam that gets injected into the boat with floorboards on (per manufacturer when I called to pick their brain).
I had to do it myself, because unfortunately with weldcraft, 1st owner gets a lifetime warranty, 2nd owner gets nothing. I got the short end of the stick as a second owner.
What happened to mine, on installation of the foam, some of it over expanded into a couple of drain channels, and essentially blocked them off.
I had to cut a portion of the aluminum out underneath to get to the drain in question.
Called up weldcraft and went over blueprints and engineering drawings, worked with their engineers to figure out where I could cut a section away that wouldn't hurt structure.
Found my point, cut my access patch in and went to town on getting the foam out.
Got.it cleared and did a re-pour of the 2 part foam, wanting to keep things basically stock the way they came..... we'll, that bit me as I had to remove more foam all over again....
As it sits now, I took most of the foam out, drilled extra drain holes being mindful of structure, and riveted my access plate back in. I pull my floorboard once a year, pop my access plate under the floor out, make sure it's clear, rivet it back in and put my board back down and everything is good to go.
Long story short, ditch the foam and don't look back.
I'll post pictures.