thermostat cover plate frozen to cylinder head

[stilllearning6]

Yamaha 4 HP -- 1996 -- the bolts have been removed which secures the steel cover plate over the cylinder head for access to the thermostat. The steel cover plate appears to be frozen to the cylinder head . Any trick to remove it ? So far , just did some heavy handed tapping with a hammer and wooden board to avoid cracking the head . I'm reluctant to pry with a metal blade/ chisel /screwdriver. Any solvents ?

 

[Clay]

Re: thermostat cover plate frozen to cylinder head

I know mercury glues theres on with silicone adhesive. you need a stiff putty knife with a sharp edge. carefully pound it in till it breaks loose. I've heated the head in water (185*) and had some success

 

[stilllearning6]

Re: thermostat cover plate frozen to cylinder head

Thank you for the help . Last night I was fortunate enough to use a bigger hammer --it worked. Any idea if the gaskets need an adhesive as in an auto?