I think the most likely problem is the engine is either hydrolocked- in
which case pull the plugs and try starting - see if water comes out
-(this can happens if you turn your engine off when its in gear) 2nd it
could be that there was no lower case gear oil - in which case your
lower unit is gonna need some serious repairs, it could be the gall
bearings but I don't think that would stop the motor from cranking