pdqubet

I'll start off by saying, I'm a newbie. I was given a '96 Tigershark 770 without knowing what was wrong with it. Clue.....it doesn't crank. I charged the battery, checked the plugs and made sure of no obstruction underneath. I could hear the starter trying to engage, but to no avail. My thoughts are that the engine is seized. My question, can I turn the engine over with a wrench, or at least try? Sorry about the basic question, so be gentle. : )