Mercury 850

[Rikkie bell]

I had to patch wiring on motor side of harness.iam just helpping rev. AL this is all free. work andit's turning into a snowball

 

[Chris1956]

A distributor ignition model derives spark from battery voltage. The stator only serves to charge the battery. So missing spark is not the stator's fault.

At this age, a lot of the spark plug wires are bad and arc to ground. They are solid stainless steel wire cored, and should have zero resistance. You should hear them arc to ground. They will have a snapping sound.

I would switch a wire and see if spark returns to #1 or #2 cylinder. Spark plug wires unscrew from the distributor cap. The rotor is nor removeable and fragile. if you break it it will be $250+ to replace it.

if the cylinder will still not run, with a known good wire and spark, the motor can suffer from water infiltration. Since it is the top cylinders, the cause would be a leaking exhaust cover or exhaust baffle.

 

[dwco5051]

If the change in plug wires makes no difference I would think about the top carburetor. Take the air silencer off and move the throttle back and forth and check that the linkages are moving the butterflys together and the chokes are moving together. If so maybe it is time to at least pull the top one for a good cleaning.

 

[Rikkie bell]

First of all rev.Al said God bless you all,and just wanted thank for all the help and different ideas.I do have spark on all cyl,but it is only running on 3and4,iam going to start pulling all spark plugs recheck comp,omh all wires,then I'll go to carbs

 

[dwco5051]

First get a spark tester. Even a cheap 4 dollar on like this will show if you are getting the same spark on top two vs bottom ones. Since it is the top two cylinders that are not firing what is common to them? One set of reed valves and one carb. I am not discounting water intrusion either but lets start with what is easy.

 

[Rikkie bell]

Well I went and got spark tester there all about the same. When I omh wires#2 had tested bad, I put 12 gage copper in it place to test it #2 started to fire.
And started pushing oil and water out exhaust manifold! Look like a big job,and then what about parts.
I did mark all cyl at TDC just to check firing order and it was ok

 

[Rikkie bell]

Is it the baffle that will cause leak? Or the manafold or both. I did see a baffle for on ebay for 55$ seems like a good price I'll look for manifold or can I it surfaced? And again thanks for all your help!!!

 

[Rikkie bell]

Now iam looking for some help tell with how exhaust manifold come off. iam hoping the power head doesn't have come off any help would be greatly appreciated

 

[Rikkie bell]

I have beenreading o.ther post. And from what I read the lower unit has to come off, and power head has to be pulled? So exhaust cover and baffle will come off Is this true. I might bitting off more than chew

 

[Chris1956]

That engine doesn't have an exhaust manifold. It has an outer water jacket cover on the port side. Under that is a baffle and under that is the inner water jacket cover.

The exhaust covers can be removed, without pulling the powerhead, but it is very hard to do it that way, and if you break a bolt, which is likely, you will then need to pull the powerhead.

You might source and inner water jacket cover and a baffle before taking it apart. Does the outer cover leak?

 

[Rikkie bell]

I couldn't see exactly we're it was leaking,but it was leaking badly. I had lower cowling on and it steady stream down back middle of mid lower exhaust housing. Is very hard to pull power head. I don't a manule but iam pretty handy. I would do water a pump since lower unit has to come off. This motor is on boat and has power trim that is not working

 

[Chris1956]

The drain hose is on the telltale fitting on the head, right?

Those motors usually leak at the water jacket cover on the cylinder head, around the spark plugs. If you dry the area of leaking off and apply some silicone caulk it should stop leaking.

The motor does not have a removeable cylinder head, so there is no chance of water leaking into the cylinders from the head.

 

[Rikkie bell]

I found outter cover and baffle but haven't found inner water jacket cover.
This motor has had a lot of different people working on it in the 45 +yrs it has been around.
I told Rev. Al finding good parts is going to be hard. I said I might take it apart and see if icoould jb weld it?

 

[Chris1956]

The baffle is under the outer water jacket cover, on the starboard side of the motor. The inner water jacket cover is under the baffle. It is pretty obvious, as it has many bolts. Those bolts are epoxied into the block. You probably should use some heat to break the epoxy bond.

 

[Rikkie bell]

Thank you for all your time and knowledge it is very appreciated!!!

 

[Rikkie bell]

Rev AL said he doesn't want to put so much money into 45 yr old motor.parts are hard to find, good ones very hard to find. But I thank you all for your help and know how.