TOPIC: Mark 55 teardown - stuck - pic and question

I have powerhead out and all bolts/nuts around perimeter removed other than the few with the lock tabs - the cover will not come off but does move up enough to get a screwdriver in between it and main block - I am afraid to lever much on this and would like to know if those bolts with lock tabs also need to be removed - I was assuming they hold something inside in place.
Thank you
PS the bolts you see still there around perimeter have nuts removed the bolts with tabs are preventing them from being taken out.

Remove the reed cage bolts with the tabs and the main bearing bolt to remove the cover. tabs must be bent open to do it.

Thank you - once the cover is off I am going to mark everything and remove the crank shaft - then need to inspect and see what is causing the problem.
Do you have any suggestions for cleaning products for the nooks and crannies in the cooling system?

call me 1 914 310 7086.
you do not have to go inside for the cooling system. call me before you pull the crank.

I have the crank case cover off now - everything inside looks pretty clean to me with little or no sign of rust however nothing moving - I understand everything comes out as a unit - so, if I do happen to get it to move and take out the crank/pistons etc I am assuming I need a specific ring compressor to get that all back in again? I really want to see if I can get it freed up without having to do that though.
Lee