fiberglass tub water issue

Went to put my rock rails on today. Drilled into the body and water came out. I was 3" from the bottom of the tub. I drilled a hole in the bottom of the tub in between the double wall. I got about a gallon of water out of each side. Not sure yet where it came from....

 

you should put a drain hole in each side to let the water drain out, because eventually the fiberglass (without a Gel coat) will absorb moisture and blister/delaminate. I have had a similar problem on my laser sailboat.

 

That was my fear, that the water would cause rot issues in the untreated fiberglass in between the walls. My second concern is winter and the water freezing in there and breaking the body.

 

Could the void be filled with something like Great Stuff to keep moisture out?

 

I thought the void was filled when the tub was made. Evidently there is more room in there than I thought. There is some foam type substance that is visible looking along the inside of the body between the inside and outside. It can be viewed behind the dash up by the firewall. I don't have time to worry about it right now. When I get back from my trip I plan to check it out further. For now I just drilled some drain holes.

 

Maybe, but the expanding foam could also split the tub if it has nowhere to escape.

 

You could then use the low expanding version that's for door jambs and windows, since a lot of expansion around those is undesirable.