#3 cylinder plug fouling? 1984 Mercury 50 hp.

[R B]

Any tests I should do while engine is running? The ignition systems tests good when off going through the manual tests. I need this motor running in two weeks for a fishing trip so I am getting desperate.

Should I change plugs to the Champion vs NGK?

Wi / Il boarder area, anyone know a good repair shop?

I noticed a very slight leak in the top carb bowl so I replaced that gasket. But that would of been #1 & #2 cylinders.

 

[Bosunsmate]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

Check when running that spark is consistent with a timing light on plug 3
Check compression too

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

Compression was good and I may chech when dark to see if I am losing spark somewhere?

How do I check the reed valves?

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

I ran it in the dark and is the porcelain suppose to glow on the plugs? Saw some (very little) spark around the #1 wire at the coil.

 

[Bosunsmate]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

No, it should be all dark

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

No, it should be all dark

I did order new wires and will probably put a new set of plugs in.

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

No, it should be all dark

Corona Effect:

In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor that is electrically energized. The discharge will occur when the strength (potential gradient) of the electric field around the conductor is high enough to form a conductive region, but not high enough to cause electrical breakdown or arcing to nearby objects. It is often seen as a bluish (or other color) glow in the air adjacent to pointed metal conductors carrying high voltages. Spontaneous corona discharges are undesirable where they waste power in high-voltage systems or where the high chemical activity in a corona discharge creates objectionable or hazardous compounds, such as ozone. Controlled corona discharges are used in a variety of filtration, printing and other processes.

I came across this on a Corvette forum.

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

I noticed I never have to pump the fuel bulb to start the engine. Is this odd especially when the motors is cold?

 

[Bosunsmate]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

Yes the corona effect will reduce the spark intensity in the #1 plug.
Did you manage to check spark consistency on 3rd cylinder?

Thats nice not having to prime the motor. If you hook up the fuel line before opening the air vent on the tank that often happens when the tank is pressurised from any heat/sun.

 

[Bosunsmate]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

Have you checked the compressions? 3rd cylinder?
Is the problem that it is running rough?

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

Have you checked the compressions? 3rd cylinder?
Is the problem that it is running rough?

Compression is at 120 on all 4 cylinders. I give up at this point as I have done what I can and appreciate the help. I found a guy (2 Hour Drive) that will look at it and repair it for a considerable amount less then a dealer. Wish me luck!

 

[Bosunsmate]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

Gook luck and journey.
Please post back what is found out

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

I will. It is hard just sitting here not being able to tinker with the motor?

Do you think 800 is a fair price for a 1983 40 hp mercury?

 

[Bosunsmate]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

Maybe in spring, less so in autumn

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

He suspects two weak coils but states my pump is not pumping water. I recently replaced the impeller and I know water was pumping when I had it running at my house. Maybe running it often off ears could wear the impeller out fast? He's installing two new coils and an impeller so I hope my problem is solved. Will update when the work is done.

 

[Faztbullet]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

My bet is bad bias in switchbox as coils rarely fail on a Merc

 

[brnschoneck]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

y u dont wanna run it dry always always have muffs on it or in the water ...

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

My bet is bad bias in switchbox as coils rarely fail on a Merc

Two coils replaces, new pump installed and it runs decent to about 50% throttle. He tested the motor warm and states the switch box is faulty causing #3 and #4 to not fire. Parts ordered for Wednesday. Here's hopping to make my trip on Thursday.

 

[R B]

Re: #3 cylinder plug fouling? 1984 Mercury 50 hp.

He replaced the switch box and says it now runs the way a 50 HP Mercury is suppose to run! Looking forward to my fishing trip now!