I am looking to secure my battery in the back of my boat. I have tried screwing them down, but put some holes in the boat. Also the screws just brok off after about 4 months. A guy told me to use epoxy. Could someone tell me what epoxy to use.(brand and where to get it) Thanks in advance.

what about the holes in the boat?

for gluing battery hold-down trays to the floor, I think I'd sand the area pretty well then use something like devcon 2-minute epoxy (walmart, homedepot, etc.), got some loctite brand epoxy at (I think) pepboys once, that might be about the best I've come across.

Screws breaking off - there has to be a reason, I'm curious about that. Did the screws themselves break, or did they pull out of a rotted floorboard?

We really need more info. If the screws or bolts are pulling through you might try using a backer to spread the load and increase support. I can thing of several ways to solve this type of problem but more info would help to narrow down the possible solutions.

If you do use epoxy, keep this generality in mind:

The slower the cure the better the bond.

marine tex available at bps