I am assuming this is either a Mercruiser, OMC Cobra or late model Volvo Drive.

You need to purchase a product called PB Blaster from your local NAPA store and soak that pin for at least 24 hours. Then take a rubber mallet and beat it out. If the rubber won't move it, switch to metal and a brass punch. If that fails, use the hammer and then you'll have to replace the pin.