Left the boat sitting too long and now can't open the engine compartment lift to access the batteries due to a dead battery. Will a cigarette light style booster/charger do the trick or do I need to take more drastic measures?

That should work as long as the lighter works with the key off. Another thing you can do is connect a charger up to your fuse board to the pos and neg coming in to it. Small charger, I wouldn't go over 10 amps max. Let it charge slow for a while.

Can you access to apply power directly to the back side of the hatch switch?

I have had this happen also. Some battery chargers will not actually start charging a totally dead battery. Easiest is like was said before, just hook up to the power lead going to the fuse box and to a ground. I have had to hook up an actual battery to open my hatch before, due to the type of charger I had. I have also had to hook up a charged battery to a low or dead battery to trick the charger into actually charging the dead one.

i once use a power pack at the fuse box and just open the hatch.

X2

Thats the simplest way if you can get to the back of the switch.

Sell the boat (quick)
Mine has a pos and neg post behind the dash just for this.. yours may too.

And once you get the hatch open, install a onboard charger and all you will have to do is plug it in..

+1

AMEN to that!