Have you tried using your driver/drill with impact setting??

I use a soldering iron to heat up only the screw instead of heatgun which by the time it heat up the screws enough lengthwise to soften the epoxy around it it also turns the surrounding surface area crispy brown .
using an impact driver like Cisco said is the way to go and TIGHTEN the screw first to try and break the seal . That way if you round the head before you break the seal you have another go at it opening it. Also use a pointy knife like a Stanley to clean any epoxy from the slot first so the driver bit goes in all the way.

Being in the stainless steel industry I would strongly advise not to use an impact drill. An impact drill will round out a stainless philips head screw faster than Flash Gordon as you can not get enough down pressure on the drill. Use a hand impact driver as they put a lot of down pressure as well as turn.
As said previously some heat from a soldering iron could also help. If the screws are very tight there is every chance you will twist the heads off any way.

Thanks for all the replies. I will certainly try to heat first with a soldering iron. I'm a bit hesitant to wack it with am impact driver. I know boats can cop a beating, but none of you have ever seen me with a hammer. Do you think a FG deck (under the teak) would be up for it?

Toph said..
Thanks for all the replies. I will certainly try to heat first with a soldering iron. I'm a bit hesitant to wack it with am impact driver. I know boats can cop a beating, but none of you have ever seen me with a hammer. Do you think a FG deck (under the teak) would be up for it?

If the FG deck underneath isn't up to it I'd think you got more than a few raised screws to be concerned about