evinrude 55 lower unit stuck

[sea raider112]

Hi please please help. I bought a boat with a 1978 Evinrude 55 engine and out on the lake today I hit a rock right out of the ramp. It is not the shear pin or linkage but the engine will not turn. I can not turn the propeller with the engine in neutral like I could before. Any help would be greatly appreciated.

Thanks in advance