mercury 402 1977

by john
(new cumberland )

mercury 402 1977

The engine will not shut off using the key switch. This was a used boat purchase, and the engine runs great, I can only shut the engine off using the choke however. I do not have a manual or a wiring diagram and that would help me troubleshoot. Can i still get that? And any advice at troubleshooting steps are appreciated.
thanks