I have a 2009 mercury 25hp 4 stroke EFI. It has been sitting for about two years with no fuel in the system. Now it will not turn over. The flywheel will spin but the engine will not fire up. Replaced spark plugs and tested spark, that did not fix the problem. After running a few years if I remove the number one spark plug it will crank up and idle just fine. There is no fluid in the cylinder so I don't think it is hydro locked.