My boat engine that will not turned over by hand and I am looking for
help to isolate the problem.

I owned a 1985-V4-90HP Evinrude engine that has been running good for
the last 7 years. I last drove the boat on the trailer on 08/30/2006
and I parked the boat for a month then and on 10/1/2006 I had the boat
in the water and the engine would not turned over. I have isolated that
I do not have a Motor Starter problem. I had all four spark plugs out
and could not turn the flywheel 1/8" either direction. I removed the
two head covers and then examine the four cylinders, pistons, and head
covers body and they all looked normal. There were no sigh of metal
shavings or heat damage in any of the cylinder. I can feel the slack
between the piston and the rings on all four cylinders.

How do I check to see if the piston rings have froze up? Is there a
safety device that may have come undone that keeps the engine from
rotating? Can I use force on piston head to try to break loose the
engine lockup?

Any comment would be greatly appreciated.

Thank you.