Probably there was never one. With few exceptions most boat builders did not have wiring diagrams. I think 1990 was the year Brunswick bought Fisher, later sold it to Tracker and stopped making them all together about 10 years ago. For trouble shooting you have two separate electrical systems. One for the motor and one for all the other things. Wiring diagrams for all major engine makers are available but for the boat you will have to search for "generic boat wiring diagrams". Also find the chart for standard color codes for boat wiring. You may face the problem that on a 30 year old boat you don't know how many people may have worked on it and changed things. Also the marine environment causes a lot of corrosion of wiring and connections. Trouble shooting boat wiring takes some knowledge and experience.
