1976 Mercury 850 value

[hockeynut19]

Not sure if this is a correct place for this question...
I have a 1976 Mercury 850 Thunderbolt and was wondering the value of this motor.
Bought it on a hunch it would be a good backup motor for our pontoon boat.
Guy I bought it from said he never had it started. I put muffs on it got it started (after fixing a fuel leak at the fuel pump cover. this thing runs like a champ!
The lower unit has some old cosmetic damage but the prop turns great.
What is this motor worth? TIA

 

[jimmbo]

Probably a lot less than it is worth to you. It is just about 47 yrs old. And motors that age need TLC and often a lot of parts replaced just to keep running, and a lot of those parts are NLA, though some can be found as NOS at dealers, and on ebay.
If you keep it, before you run it again, tempting Fate, put in a new Water Pump Impeller.

 

[Faztbullet]

$400-$600 in my area

 

[hockeynut19]

Probably a lot less than it is worth to you. It is just about 47 yrs old. And motors that age need TLC and often a lot of parts replaced just to keep running, and a lot of those parts are NLA, though some can be found as NOS at dealers, and on ebay.
If you keep it, before you run it again, tempting Fate, put in a new Water Pump Impeller.

Ok thank you. My dad was a Mercury guy he loved them but back then you could get parts. I thought of refinishing it as I am a autobody tech, as a tribute to my long gone
pops.

 

[jimmbo]

Ok thank you. My dad was a Mercury guy he loved them but back then you could get parts. I thought of refinishing it as I am a autobody tech, as a tribute to my long gone
pops.

I like/love the Older Inline Mercs, but I also know, just about everyone of them suffers from decrepit Wiring(bad Insulation and copper dust inside), and issues with the Water Jacket gaskets inside the Exhaust Chamber on the Block. Also Parts are getting Scarce, and finding mechanics/shops that will work on them, make the Parts Shortages look mild.

 

[Chris1956]

You might be able to give them away in my area (salt water), but not sell them. The blocks get real brittle and corroded from the salt over 47 years.

You would need to be able to do any maintenance/repair on them yourself, as no shop here would touch them. If you plan to run it, pick up an OEM service manual for it.

New gear oil and waterpump impeller are minimum. Cleaning of carb and replacement of carb gaskets, inlet needle and seat plus floats are standard maintenance items. These items should be widely available.

A 1976 Merc 850 would be the first 4 cylinder with ADI ignition(4 coils). If it has a distributor, it is 1973 or older. Inspect engine and boat wiring harnesses. They are usually bad by now. Replacements should be avail on the web.

I happen to think they had real good power for their weight and compactness.

 

[The Force power]

Don't "play" with the timing/primary & secondary pick up (if not necessary or proper manual) their are a bore to set-up correctly
As Chris1956 said; they're good motors ($600+ in my area)

 

[jimmbo]

A 1976 Merc 850 would be the first 4 cylinder with ADI ignition(4 coils). If it has a distributor, it is 1973 or older.

Okay, I'll bite. So what Ignition System was used between the Distributor models of 73 until the ADI came out in 1976?

 

[merc850]

Okay, I'll bite. So what Ignition System was used between the Distributor models of 73 until the ADI came out in 1976?

1975 and older used a distributor.

 

[hockeynut19]

You might be able to give them away in my area (salt water), but not sell them. The blocks get real brittle and corroded from the salt over 47 years.

You would need to be able to do any maintenance/repair on them yourself, as no shop here would touch them. If you plan to run it, pick up an OEM service manual for it.

New gear oil and waterpump impeller are minimum. Cleaning of carb and replacement of carb gaskets, inlet needle and seat plus floats are standard maintenance items. These items should be widely available.

A 1976 Merc 850 would be the first 4 cylinder with ADI ignition(4 coils). If it has a distributor, it is 1973 or older. Inspect engine and boat wiring harnesses. They are usually bad by now. Replacements should be avail on the web.

I happen to think they had real good power for their weight and compactness.

Thanks for your response, I will be able to work on this motor to a point. I am looking for the Mercury manual and I have the parts manual. The gear case oil was aged and I replaced that which should have been done with the water impeller but oh well I wanted to see the condition of the oil to start with.
It runs really nice. The lower unit case is a little rough but ok, some of the wiring has been replaced and insulation has been repaired with liquid type insulation. It had a fuel leak at the fuel pump cap, fixed that and she starts every single time on the first crank. This motor for sure has been in the Midwest United States out of Wisconsin then in Indiana all fresh water.

 

[merc850]

Replace the motor wiring harness and it will be worth more and be safer too.

 

[hockeynut19]

thanks for your response. The main engine harness has been replaced, its the ignition harness that is a in question. looks like it was a $20 part at one time.
part# 84-73362A1 it is not available. ...

 

[The Force power]

Replace the motor wiring harness and it will be worth more and be safer too.

True to that!
Old corroded wire leads to misdiagnosing the ignition-system
I fixed up a few of these classics & replaced wire for wire till the last one under the cowl

 

[Chris1956]

Part 84-73362A1 looks to be the harness from switchbox to each coil. So get some ring terminals, and 4 different colors of wire and a soldering iron and make one up. Be glad is it not an exhaust baffle that you need.

You have an ancient motor. Non-tune up stuff is going to be NLA.

 

[hockeynut19]

thanks Chris that is what I will do over the winter months if I get bored and keep it!
I have been looking for a Mercury service manual and wiring diagram if anyone can help that would be great!

 

[merc850]

The internal harness is the most important as it carries power to the starter
(lots of current)
Mercury Marine 414-3369 Internal Engine Harnesses - CDI Electronics
Price: $203.59 from this site
Wiring diagram

 

[hockeynut19]

Thank you

 

[The Force power]

You should tear into the wiring in the control box as well, open it up & you'll see

 

[The Force power]

Thank you

Check the trigger-wires they tend to corrode around the area where they're going under the fly-wheel and can cause misfires.
Don't cut corners when you are replacing wiring, it will come back & haunt you

 

[hockeynut19]

You should tear into the wiring in the control box as well, open it up & you'll see

The control box has been replaced it has a date of 4/16/1989 stamped on it. Not to say that’s when it was replaced but yes it’s old…