Best way to unfreeze piston’s?

[333Fitter]

I picked up a Evinrude light twin with pull starter already removed and I’m unable to turn motor over by hand.
Motor had head already off it appears the pistons are seized.
My question is what’s the best way to unseize motor ?
I currently have it laying on back with pistons facing up soaking in PB blaster.

 

[fdrgator]

Do what you want, but I'd disassemble the whole powerhead. There's likely more of a problem than just the pistons. Forcing it to turn will destroy the connecting rods if there is rust in there.