Should I routinely replace the impeller in my Mercruiser outdrive as preventive maintenance?

Question

If so, how often? It is a 1978 Type I

Answer 1

Most manufacturers say once a year or after a long period where it could have a chance to dry out.  If you notice the motor overheating shut it down, could be a sign of impeller failure.  Repairing the engine can be significantly more costly than replacing the impeller regularly.