Logo

Spark plug black holesdots damaged

sashko12

Member
"Hi,

I have a strong spark


"Hi,

I have a strong spark out of the spark wire to the motor chassis. The motor dies only when in the water and under the load. Looks like the combustion pressure "weakens" the spark.
After examining the spark plugs I found that there are tiny black holes in the ceramic insulator all around within the same circumference.
Is the spark escaping from there to the chassis when under pressure?"
 
What engine? what plugs?

if


What engine? what plugs?

if in doubt about plugs replace them!
 
"ok. another detail, that migh

"ok. another detail, that might become major solver...

I had some silicon dielectric grease over the ceramic part of the spark plug. Should I have not done that? And used dielectric grease only on the metal tip of the spark plug where the wire connects to it?"
 
First of all I know your Plugs

First of all I know your Plugs have nothing to do with the issue you mentioned.
However if you suspected arching on the plugs simply start the engine with the cowling removed on the water during the night or late evening you will clearly see if its sparking.
 
"your problem could very well

"your problem could very well be the spark problem......... no spark no run........ if you are arching you are losing spark.....

if you have black suit deposits on the ceramic then you need to replace the plugs. it means they are bad.....

how long have you had this eng/boat?

how old are the plugs?

any discolored, peeling, or chipping paint on the eng?

what are your idle rpms?

how long has the prob been occurring?"
 
"To Andrew Mack.:
I don'


"To Andrew Mack.:
I don't think the problem will show itself using the spark detection method you describe since (to my understanding) the pressure in the motor itself makes the spark ark somewhere else but in the motor. i.e. current finds a path of least resistance.

To David Real:
I had this Boat + motor for 4 months; on the water - 4-5 times. First two times had trouble starting the motor but after cleaning the carbs and replacing the spark plugs (put new QL77Jc4) I was able make it run excellent. Then after having this motor run for solid 25-30 mins during a fishing trip and after the motor was shut down. I couldn't put it in gear. (Note: it started up fine and idled ok).
I cleaned all the distributor parts and thought it might had fixed it. But no, same exact problem!

Didn't see any discoloration on the engine. Some paint chipping, possibly because of the maintenance(?)

Idle RPMs - don't know at this point - I'l be installing the tach after I make the engine run as it should. I'm affraid to add additional complications to the whole "non-working" situation.

Thank you for any help. And apologize for a prolonged text."
 
"Update....

Replaced the pl


"Update....

Replaced the plugs. Went out to the launch... I was ready to sink it!!!!

How possible is it that I'm having bad fuel? The reason why I'm asking is because before I replaced the plugs I saw some milky colored substance on the lowest #3 spark plug, there was also just a small amount of that whitish colored greasy deposit on #2 (middle) plug, and almost nothing on the top one. Are we talking water in the fuel and that's why it cannot combust properly?"
 
"Steven O , A spark is NOT and

"Steven O , A spark is NOT and injection, it has absolutely nothing the do with back pressure. Spark to lease resistance yes, old broken wires etc..
Water in your fuel ? Connect an external tank and remove this from the equation !
At this point you need to do a compression check 2 much water in fuel = blown head gasket, water does not compress well !"
 
"As usual, wrong.

The compr


"As usual, wrong.

The compression in the cylinder, the fuel/oil charge, the rate of compression rise in the cylinder as the piston rises in the cylinder, ALL come into play with regard to the strength and temperature of the spark generated when the plug fires.
It is sometimes known as "spark quenching" and is an undesirable (and unavoidable) effect that occurs in the cylinder.
The reason that a 7/16" gap tester is used to test spark on OBs is because, a good rule of thumb is that if the spark will jump 7/16", it will not be affected by quenching. A weak spark will jump the .030 gap of the plug electrodes when the plug is held to the block and observed, but it may be completely dead when installed and quenched in normal operation.

Get it Andrew? By the way, water does not compress AT ALL!!!!!"
 
Thank you Doug. Because I was

Thank you Doug. Because I was getting confused!

I have 130 psi on #1 and #2 cylinders and 125 PSI on #3 (bottom) how do I know if the head gasket is OK?
 
"Doug. Thankyou for adding tha

"Doug. Thankyou for adding that about the spark. Ive been in the automotive repair trade for 35 yrs. Ive experienced spark blow out many times and at one time had a whole set of new plugs that wouldnt fire under compresion. I belive it was A/C that put out a plug cleaner with a spark tester built in so you could adjust the air pressure and while the plug was fireing in the machine you could watch the spark stop if the plug was bad. Wish I had one of those now, Sure makes the final decsion if a plug is bad or not!! Kudos Doug!"
 
"Those compressions look very

"Those compressions look very good. No head gasket or cylinder damage apparent from those readings.

Regarding the black dots...who knows, but as VicS says, just get new ones for now.
Silicon dielectric grease....hmmm...
So much to say on that one. The grease you used may be spec'ed to only withstand low voltages. By low, I mean less than 500 volts. Yes, that is considered low.
When you compare it to the normal spark voltage present on the spark plug wire...in the neighborhood of 20,000 (yes, twenty thousand) volts...maybe higher...then 500 is low.
So, using a grease on the plug and boot to protect from corrosion may not withstand the very high voltage present, and you may not even be able to predict what would happen. Burning, arcing, etc. High voltage will do some strange things...

Time for new plugs, new wires, and just think, it is half the cost that it would be for a V6!!!"
 
"I "GET IT DOUG" seems

"I "GET IT DOUG" seems like we putting a man on the moon here
Lets sit back and troubleshooting of spark here..I see my ideas were swept aside with sarcasm ..Then why is Steven worried about the head gasket ? Lets fix SPARK ! Stay tune !!
And we moving along ..."
 
"Doug I will "get it"

"Doug I will "get it" and stand corrected when Steven resolves this and post an honest reply with corrective measures taken, At this point I don't think its a spark issue period. At the end of it all I will learn. FACT is he is clearly posting a 10 percent variation on one cylinder clearly shows something is amiss here, Spark has nothing to do with this, read this post carefully.
On Aug 6th I clearly pointed out PLUGS has nothing to do with this. Four days later he changed the plugs now he ready to sink it.
Just trying to help and getting trash for nothing..by a so call PRO
"
 
"StevenO at 3:42 today:
"


"StevenO at 3:42 today:
"I have 130 psi on #1 and #2 cylinders and 125 PSI on #3 (bottom) how do I know if the head gasket is OK?"
AndrewM at 5:47 today:
"At the end of it all I will learn. FACT is he is clearly posting a 10 percent variation on one cylinder clearly shows something is amiss here"
Also he says:
"read this post carefully. "

Andrew, where is the 10% variation?
Back to elementary school math for you....."
 
"Gents,

this is not a place


"Gents,

this is not a place or time to get nervous ;) The only guy who's nervous is me - I've been fighting with this issue for more than 2 months already!

Some recap - I bought the boat + motor 3 months ago.
Initially nothing worked - couldn't fire up the motor at all. Replaced spark plugs, cleaned (I mean really cleaned / rebuilt) carbs and she started. With some tune up was able to ride it. On a local lake it was performing perfectly.

One day I took it out for some fishing. 30 minutes drive to fishing spot... Shut the engine down ... 10 minutes of "fishing".... Time to change a fishing spot.... Started right up just fine ... Put in gear and a little bit more forward (just a bit) -- DEAD!!! Second try - started fine -- in gear -- DEAD!!! 3rd try -- in gear .... almost dead, please...please... revved up and off I went!!! Thought it was just a one time thing - nah --- second turn off of the engine and try to restart and put in gear --- DEAD!

Cleaned distributor, wires, took it too the lake - can't accelerate at all! Dies at a first attempt to apply some power.

Since then replaced ignition coil (brand new), checked spark, checked compression (130,130, 125), I'm sure the fuel gets into the cylinders - the sparks are getting wet. Spark does jump 1/2 inch easily (using a nail in the spark rubber boot to the chassis)!

Spotted black tiny holes in the ceramic part of the spark plug where the rubber boot is positioned - thought it was relevant to the issue.

What else could be there?

Please help me out here?!"
 
Since even the blind or the ar

Since even the blind or the arithmetic challenged like my self could have read through this and see I meant 10 LBS not percentage goes to the elementary saying I learn..
Cross all your T's and dot all your I's because some fools would not be able to read through it.
Stop the bickering like you love to do ( I seen you in action like this before) and get back to helping folks out. I seen your history on here slanderous and discredit makes your day then this is your day have fun.
 
"Oh, I see,,,you meant ten pou

"Oh, I see,,,you meant ten pounds difference....
I see...I think....
But, but, but,

I read that he says only 5 pounds difference....
you remember 130 - 125 = ????

I will get to helping the folks here, by trying to get you to STOP POSTING.

Your posts simply confuse people."
 
"think ill add my 2 cents to t

"think ill add my 2 cents to this. After rereading all these posts It seems to me that you have a fuel problem not electrical. Im thinkin if you were to reclean and recheck your carb work , replace any and all fuel filters, including checking to see if there is a filter that you havnt noticed, and blow out the fuel lines from tank to carb. I think you might correct your problem. Maybe there's a fuel/water seperator in the system you dont know about??? No tellin what previous owners have done?????? Worth a shot anyway.......remember, all's it takes is one tiny little piece of crap in them carbs to ruin your day!!!!"
 
"Back to the problem , You nee

"Back to the problem , You need to do a Stator and trigger test if you need the instructions PM me and I will send you the PDF some here may think this is top secret also."
 
"Ok.

My biggest suspect at


"Ok.

My biggest suspect at this point is the water in the fuel


My debug path for now is this:
1) attach external gas tank with fresh 87 Gas;
2) flush carbs of old gas;
3) put again very brand new plugs in;
4) and try it out.

If this does not work then I will proceed to (re)cleaning the carbs again.

Any suggestions?

Ps- what's "stator and trigger test"?"
 
"Also,

what's my proba


"Also,

what's my probability that I did not adjust the floats in the carbs correctly? Could that have some impact? What usually happens if the carbs are overfilling with gas because of the bad float adjustment?

Thank you guys."
 
"Steven ,
Please lets isolat


"Steven ,
Please lets isolate the issue from Fuel & electricity first then its a breeze to resolve.
I agree with your steps above lets hold off on the Stator and trigger test for now. I have the instructions its in your manual also.
I have personally re-build carbs twice in a week on a friends motor if this means anything to you.
If the carbs are overfilling as you stated you will observe excessive smoke oil slick in the water, foul plugs , and oil running down the leg of the engine.."
 
"Just out of curiosity did you

"Just out of curiosity did you say you put grease in the spark plug boot (so it will contact the conductor on top) and around the insulator?

Before you go much further, because I believe in KISS, clean all of the grease out of your boots. Use something that will cut thru the grease and leave you with only rubber left behind. Now do the same to the plugs. The ceramic should be clean and dry. You can use the dielectric spark plug specific grease but only on the metal conductor cap/brass wire conductor.

Try that and then go on to testing the rest of your motor."
 
[i]"I have personally re-b

"I have personally re-build carbs twice in a week on a friends motor "

Only twice ? I think I stripped and cleaned one that had got salt water in it abour 4 times in one afternoon before I sorted it out. And it was only a piddly lttle Bing carb on a 5 hp Volvo Penta
 
Ok... I can't say that I n

Ok... I can't say that I noticed too much oil in the water and the engine doesn't smoke too much. Only when I over choke it ... it happens. So what you are saying is that it seems like the floats are adjusted correctly?... OK.... But the plugs are getting wet - that's for sure! AND there IS a strong spark! I'm so anxious to try a different gas tank! Can't wait.

Thank you.
 
"To Chris:

yeah man, I had


"To Chris:

yeah man, I had dielectric grease on the ceramic part as well - stupid me! I cleaned it with electric part cleaner/dryer spray. Tried it in the water - just a bit better - can hold the gear for more time but dies just as I apply a bit more forward.
Note: the motor most of the time would not die if I just shift it into forward, but does die if I apply some more(just a bitty) power


Thank you Chris."
 
""I had some silicon diele

""I had some silicon dielectric grease over the ceramic part of the spark plug. Should I have not done that? And used dielectric grease only on the metal tip of the spark plug where the wire connects to it?"

Seriously this needs to be resolved before you spend any more time looking at the motor. If your insulators are damaged they might not be insulating much anymore. With your playing with 20,000 volts + electricity does funny things."
 
Back
Top