Why is the floor of the boat packed with Styrofoam?

Question

tri hull 18ft fiberglass. i just rippped out the plywood floor and found styrofoam. it was waterlogged so i removed all of it so now what is the right way to fix this thing up---i know nothing about boats like you havent already figured that out.

Answer 1

If the area between the hull and the floor was waterlogged, then potential bad news.  Your stringers could also be compromised.  A ski boat has longitudinal wood stringers, bonded into the fiberglass hull.  Once they get waterlogged, you will need to replace them, which means ripping them out and reglassing in new ones.   A tedious job, at the least.  But without solid stringers, your fiberglass hull won't withstanding the pounding of a planing hull moving at high speed.

Dave

Answer 2

It's all about floatation. If the boat fills up with water the foam will help float the boat. Keeping your fingers crossed the hull doesn't go right to the bottom.

My recommendation would be to put some sort of floatation back in before you rebuild the floor.

Answer 3

these answers are all good...except for the part about drywall screws.  they rust out and the deck will release from the stringers, ive replaced MANY decks and stringers in boats and see it.  spend the extra coin and use STAINLESS screws.  You want to use a 400 grade stainless, not 300.  heres a simple tip....if a magnet will stick to it, dont use it.

Answer 4

so it floats if full of water...Styrofoam doesn't get waterlogged...its a dense foam...u must mean there was water between hull and floor..u can get new foam and fiberglass repair stuff and any home repair...Lowes/home depot

Answer 5

just think about what is going on down there under the flooring and start fresh ----- you got rid of all the rotten and stinky stuff ,,, now you need to reassess  what"s to do to protect the bottom of the boat .... re-seal the hull (new marine sealer or paint,,, re-place the foam as best you can cut and fit --  leave spaces in the center of the keel for water to run to the back of the boat and out the drain ,,,,, use a marine grade of plywood and dry-wall screws to replace the floor fix any stringers that have rot and then finish with outdoor grass carpet....  this is all time consuming and do not rush the job ------ the better and tighter the floor is screwed down the quieter you boat will perform in the H2O......  good luck and if you gotz any me quesions just e-mail me ......

Answer 6

as the other said, its for floatation. the foam you removed was likely not styrofoam, but a foam that was poured in during the manufacture process. you can buy new pourable foam, and its a good idea to replace it when you put the new floor in. The foam also adds to the structure of the boat by supporting the fiberglass hull.