I have an '88 Mercury - 45 HP that I was able to get started first time out this year, but was not running right.  Took it in for a check and was told that it needed a switch box.  Installed the switch box myself and now when I turn the key the motor only clicks.  Just talked to a mechanic that suggested that I try "rotating the bendix by hand" just to see if this would let it try to start.  Don't know what the heck he's talking about.  Can anyone point me in the direction of a website or other resource that might help me understand what this is.  He seemed to think that by doing this it would save me a repair cost -- pretty good  recommendation considering I called him to schedule an appointment for repair.

The Bendix is the part of the starter that extends to turn the fly wheel. It looks like a gear. Make sure the key is off if you do this. Check you battery connections and charge, it could be the battery and not the starter at all.

Thanks, I think.  I'm pretty sure it isn't the battery.  I put in new connections earlier this year and even tried hooking it up to the trolling motor battery and got the same result.

Sounds like a starter then if there isn't any corrosion on the terminals and you have a hot battery. The clicking tells you your not getting enough current to turn the starter over. They aren't to expensive to get rebuilt.

Good luck