As Mumbles noted, removing the bypass covers will allow you to examine the rings and piston skirts and add some penetrating oil. Avoid the natural temptation to put a big breaker bar and socket on the flywheel nut and trying to force it loose – good way to break a ring or even worse. You noted you already have some “wiggle” in the pistons, so best to add some penetrating oil and rock the flywheel back and forth to work it loose. Patience here brings positive results.
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1957 Evinrude 3022
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20
1982 Evinrude 25hp
“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
