Re: 850 thunderbolt
Funny how motors always "worked well" -before storage -last season -according to the previous owner -last time it was run etc etc
Do you have a S/N for your motor or any idea of the year? The S/N can be found on the name plate mounted on the front of the transom mount and is the best identifier for the Merc motors.
Depending on what, if any, is left of the wiring harness you may be able to repair it. Most motors of the '70s vintage need to have all the internal wiring replaced. You can still buy the complete harness for about $100. There are a multitude of used parts on the market, some not so cheap though.
First thing I would do though before spending any money is to do a compression test. That is the best indicator of the condition of the motor. It can be performed using the starter motor (if its still present) or by using a pull cord if you have to.
As for a manual I would try to get a Merc shop manual as first choice. Clymers is not too bad but stay away from the Seloc brand. Just my own opinion based on what I have bought and used in the past.
