1983 seahorse 7.5hp 2-stroke won't shift into reverse

[bg9999]

The lever won't move backwards out of neutral, even when the engine is not running. Moves into forward position fine.
Is there anything easy to check before having to bring it in for service? It was working fine, but the other day it bucked up out of the water when I shifted it into reverse -- I wonder if that caused the problem? Any advice very welcome!