I have a starter on a 90 hp Mercury that whines bad when cranking. Does anybody know what would cause this? Tried oiling bendix, etc. That didn't help.

Try cleaning all the cable connections till they are really shiny. remember too that cables will corrode from the inside out. Make sure the battery is fully charged. If that does not help, then try jumping directly from a known good batter to the starter solenoid. If continues to wind, cheap first fix would be to try replacing the solenoid. If still have problems, either rebuild the starter or replace it.

its tired replace it ..