Fishbox Siliconed Shut :-(

[gman1001]

Previous owner siliconed the rear deck fishbox shut on my 1989 18'. I never found out why.

I scraped and picked as much of the white rubbery sealant out but still can't open the compartment.

I tried removing the black plastic handle so I could lift using more force. No luck. WIth the black plastic handle gone I can see in the there, it is dry, he must have put a plug on the drain from the inside.

Any thoughts on a way to get this thing open? Maybe some sort of solvent to soak around the edges?

Tx!