Ouch, that sounds nasty.  Can you dig out a piece of that glue  to figure out what it is?

3M makes a product called Debond for silicone based stuff.

WD40 dissolves a few kinds of adhesive. It works like Gunk Off.

Heat might help but that can be high risk of you overdo it.

Lifting pressure over a lot long period of time may help.  I mean like 24-48 hours between increases in pressure.

Can you bend a hacksaw blade and force it through the gap? An extra long jigsaw blade would be perfect.  

Still desperate? With a second person helping, a heated wire. Similar to electric synthetic rope cutters.

 Good luck.

You might try a osculating saw with metal cutting blades - try from the engine compartment to saw open the glue in the seam.  Will be messy and not fun... 

Harbor Freight has several types - mine lasted a long time and I now have the battery powered Chicago version. 

HTH 
Jay 

Kirby Galassi wrote:

Years back.... previous owners have glued the cockpit engine hatch shut. Appears to be a silver calking maybe  RTV. not white or black 5200.

 So now I'm stuck looking at the hatch thinking do i use a knife or a dremel tool to get it loose. maybe piano wire.. Reminds me if an oil pan from hell.

Mine was bolted and glued with what appeared to be 5200.  I tried a lot of things, including an oscillating blade - which cut into the underside of the fiberglass but did not help much with freeing the 5200.  What finally worked for me was a heat gun and putty knives in combination with a claw hammer and a small but good quality pry bar that was probably designed for removing carpet tack strips. 

I had to work slowly around the perimeter heating a few inches at a time and driving a thin putty knife in with a small hammer, then working it further around by tapping the side with the hammer as far as possible. Then heating ahead another few inches and driving in another putty knife.  And combining and alternating this with prying.  I was very relieved to get the sole free and gain access to some delayed projects.