Ing switch

[Rikkie]

I have a 1975 mercury 850 I am trying to change the ing switch stock switch has 5 poles and push bottom choke
All l could find was 6 poles push key to choke and to poles for magneto and I don't think this motor has a magneto so I need some help

it's a 7 wire harness red-battery black-ground brown-tech yellow-neutral safety gray-choke white-acc and orange?Thanks for for any help

 

[Rikkie]

Not the ing switch the ign switch

 

[Chris1956]

That ignition switch will probably work, if it fits into the control, physically.

The grey wire goes to choke, versus the old choke button you have on the control, or you can leave it stock and use the current choke button as you prefer. To leave it stock, you will need to wire from the "I" terminal to the choke button, and leave the grey wire connected to the other side of the choke button.

So the ignition switch gets red to "B", black to "I", orange to the other "I", yellow to "S", white to "A", and grey to "C" (if you want to use it).

Brown does not connected to the ignition switch, but goes to the front of the control to run the tachometer.

A 1975 Merc 850 should have the 4 coil Alternator Driven Ignition (ADI). Although it is not technically a magneto type, it is wired the same, grounding the orange wire to kill spark.

An older Merc 850 would have a singular coil and distributor and has battery driven CDI ignition.

 

[Rikkie]

Chris 1956
thank you so much for info
mine has the single coil so it's cdi
ign
the engine side of wireing harness has been replaced there are 2 wires not been used orange and gray do you have any idea what they do or just leave them taped up?
again thank you it really helps

 

[Rikkie]

Chris1956 I think you ment black goes to m and orange goes to other m
m+m off-abc is run- basc start and push key or botton to choke
again i thank you

 

[Chris1956]

Sorry, yes orange and black go to the "M" terminal. The only grey wire I know of is for the choke solenoid. You do have one, right?

On your motor, power is supplied on the white wire to power the switchbox to pulse the ign coil to create spark. Orange is not used on your motor, but Merc connected it to the boat harness, in case you wanted to use a different motor, the same boat harness would work.

 

[Rikkie]

Chris1956
thank you so much for your help!

I got it running on a stand and muff it's still takes starting fluid when cold

and it idles at high rpms it not on idle STOP screw I can move dist and get it slow down I thought you might know why
thank for your knowledge

 

[Chris1956]

You sometimes need to adjust the throttle cable to further push the throttle closed. Do not adjust the idle pickup timing.

You did check/set the idle pickup timing, right? Max spark advance should be 21*BTDC, not what the timing decal says.

 

[Rikkie]

The problem with that is this motor has no trimming pointer and no marks on flywheel?
if I had a dial indicated I would take them off my other motor

I'll try throttle linkage

thank you again

 

[Chris1956]

The TDC timing marks are on the top cowling support. There is supposed to be a timing decal with degrees, on the flywheel. It is indexed by the punchmark on the flywheel.

The timing pointer didn't come into use until 76/77.

 

[Rikkie]

Hi Chris1956
I have to 1975 by serial# 1 has pointer and decal on flywheel

I did check throttle linkage it was holding it open a little

I was just wondering were you a mercury machanic you seem to know all there is to know about everything about m them?!!!

I'll have more questions when I get new coil and rectifier for the other motor
I can't say thank you enough!!!

 

[Chris1956]

I had an '73 850 and a '77 1500, as well as a OEM service manual, covering all Merc models. Both motors were too old to take to a mechanic, and I had no issue working on them.

 

[Rikkie]

Hi Chris1956
well when put upper water pump kit in I didn't remove base were key was a little rusty but I went ahead and put together and it went well had F/R and waeter flow
a couple days

 

[Chris1956]

As long as the base is not melted and you are not getting water into the gearcase, you do not need to change the waterpump base, IMO.

If the gearcase gets water, it is likely the waterpump base. I did need to change the shift shaft seal on my '93 Merc, but never on my '77.

 

[Rikkie]

Chris1956
yes I am getting water in gear case but I think it's drive shaft wear it seals on lower pump seal sits it very rust and has no sealing surface left
this motor is the one I took off and replaced with 89 Johnson v 4 120hp
I just thought i would fix it a sell it

I do have 2 of them and I am sure l can make one good 1 and 1 for parts but then they to old to have someone work on
a parts are hard to come by

but I really thank you for all your help!!!

 

[Chris1956]

There was an item called a "Speedi Sleeve". It was a sleeve you could install over the driveshaft and slide down to cover the pitting at the waterpump driveshaft seal. It would then give a smooth sealing surface.

You obviously have a motor that was used in saltwater?

 

[Rikkie]

Thank you ill try to find one sounds like just what i need

 

[Rikkie]

Good morning Chris1956
I hope you a good 4th of July and a safe one
I found a post 73 850 that said shaft size was .984 do you know if a 75 would be the same?
on the other motor I fixed stator wires best as I could I have could and no resistance betwine yellow wires and no shorts to ground replaced coil and rectifier had spark for a couple
of cracks but nospark now?
I do have power at switcher box at red and white with key on and brown on the other side
do you have any test I should try
thank you agin

 

[Chris1956]

I believe all inline 4/6 engines from the 70s have the same driveshaft size. I used to swap my '77 Merc 1500 and the '73 Merc 850 gearcases, w/o issue.

If you other motor is a Johnny, you would be best starting another topic in the J/E forums.

 

[Rikkie]

Chris1956
no not talking about my Johnson
I have 2 1975 850 MERCURY one had bad whirring on engine that I thought I fixed up to run but I hook up battery and turned on key and the smoke came out
I replaced coil and rectifier had spark for a couple of cranks but nothing now I just thought you might know another test I could do
have power on red wire and power on white with key on and power to brown on dist.side but no spark at plugs
right now I have 3 boats 14' with 7.5 merc/18' starcraft SS with 120hp and 6hp kicker both are Johnson and 22'starcraft chieftain with 165 i/o