I have a 1974 glastron, the speedometer is not working. where do you find the old style pickup that slides in
The speedometer might not be working because of a failure in a plugged pitot tube. You also need to clean your pitot tube to make sure that it does not have any clogged debris. Go to http://www.ehow.com/how_5029988_repair-boat-speedometer.html for reference or http://www.glastron.com/ and contact the customer service for help.
The speedometer cable? It has small square ends? Maybe a speedo cable for a 73 Dodge power wagon can replace it?
Go to a marina or a Glastron dealer. Check Yellow pages online.