Mercury 850 Thunderbolt

[Lawlersell]

I have a newly acquired 850 with thunderbolt ignition. The serial is 4367074. I need help with the main internal harness the small black wire splits to two different locations and I'm not sure where those are. Any help would be greatly appreciated.

 

[Chris1956]

OK. that motor looks to be a 1976. It should have the ADI ignition with 4 coils. The black wire should go to the bottom cowling to ground it and to the starter solenoid.

 

[Lawlersell]

Chris1956 thank you for the help. When you say bottom cowling can you please help me know where that might be. I apologize I am new to outboards.

 

[Chris1956]

The bottom cowl is where the wiring harness plugs into. If not there, a good thing would be to ground the case of the switchbox (ignition component).

 

[Lawlersell]

Sounds good thank you again for your help.

 

[Lawlersell]

How would I go about setting the timing on this engine?

 

[Chris1956]

There is a procedure in the Service Manual. Since your knowledge is limited, I would suggest you pick one up. In a nutshell, you set idle timing and max spark advance. Idle timing is a timing spec (usually about 4-6* ATDC) where the carbs are just ready to open. Max spark advance is self-explanatory. After that you set idle speed, and adjust throttle cable to push throttle closed when control is in neutral.

 

[Lawlersell]

Thanks for your help again. What is the best service manual to buy?

 

[Chris1956]

A Mercury Service Manual is best. You could probably find one on-line and print the pages you need. Alternatively, you could consult the on line manual and pick up a Seloc manual in paper form, and save a few $. I like the paper copies best, but the Merc manuals are expensive, because they are better than the Seloc.