Rear Hatch leaks like a Cold War Submarine.....Help

I finished out and completed most of my breadbox..but my friend started it and one of the things he built and installed was the galley hatch and hinge...just looking at it I knew it was going to leak...I need to remove the standard piano hinge and install a hurricane hinge..I am hoping someone here can direct me in the right direction to purchasing a hinge that will work on my camper....I am looking at something like the better than hinge from Lil Bear below is what I am working with:
Top looking down across hatch


Under hatch with it open looking out

Sides

open top

the entire with of rear of camper is 51 inches the with of the current hinge is 4 ft
how wide would my new hinge need to be to stop the rain?
Top looking down across hatch


Under hatch with it open looking out

Sides

open top

the entire with of rear of camper is 51 inches the with of the current hinge is 4 ft
how wide would my new hinge need to be to stop the rain?