Mecr 850 ? idle problem 85 HP

[las4444]

Hello. New member but have been researching on Iboats for a couple of weeks. I bought a boat a month ago that has a Mercury 850 outboard. It is the blue line with the thunderbolt ignition. The seller advertised it as a 1985 motor. My research showed this was a mid 70's motor. However, the data tag on the swivel was for a mariner 90hp inline 6. Serial #A117802. This would lead me to believe the 850 and swivel met up later in life.

I have not been able to located any other serial number on the motor itself. Currently, I'm trying to identify the motor so I can order the manuals etc.

When I checked out the boat the guy ran the boat and it idled fine. He put it in and out of gear a couple of times. I had a boat shop do a compression check, which I was not present at, it ran fine then. After a couple of weeks I started it up to run the gas out. I runs great at 1000 rpm but will not run in neutral. Am I missing something simple?

I attached a side pic of the motor.

Thank for the help.

 

[crem1]

Re: Mecr 850 ? idle problem 85 HP

Try cleaning the carbs, removal and soaking in solvent then buy a carb kit for it or the fuel pump is faulty

 

[las4444]

Re: Mecr 850 ? idle problem 85 HP

I found the problem this evening. The top carb trim? idle? screw had turned itself all the way out and fell down into the cowl during transport. At least I found it. There was tape wrapped around it to hold it in place. What is the best fix? I would think originally it would have had a spring. I got the boat to start in netral. Until I fix the screw there is no way I can accuratly adjust the idle.

Does anyone know what the starting point in turns if for any old merc? I purchased a set of manuals today but like some I lack patience.

Thanks

 

[bryanwess2000]

Re: Mecr 850 ? idle problem 85 HP

After you clean the carbs start with the idle mixture screw set at 1 1/2
turns out from lightly seated. You should be able to find the serial number
on the port side of the block or crankcase cover just below the flywheel.
If yours has cd ignition its a 1976-77, if distributor its an earlier model.
These are tough little motors, I've overheated mine, ran lean several
times at wot chasing down a fuel issue, and its ran great for ~5years.
I just keep it decarbed and clean the carbs every year. The only issue
I've had is corroded wiring so I rewired the motor and made a new wiring
harness.
Good luck to you, hopefully yours will be as reliable as mine has been.