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Plug Fouling 1999 70HP johnson

L

lpickett

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"I just registered and sent th

"I just registered and sent the following to Joe Reeves,,, I would like to share my problem so, I also posted my problem here so all could benefit,

I have a 1999 70HP Johnson.... VRO Disabled,,,,,, It is on a Pontoon Boat.... Slow cruise(r)
I have a plug that fouls... lowest Cylinder... I replace the plug we and run fine for what seems like a 1/2 to an Hour and I lose the cylinder... The other two run fine and we get back to the dock with no problem. When I look at the plug it is wet (Obviously)... I have replaced the coil wires, disabled the Vro... Replaced the plugs etc...
This week I will bring my compression tester to camp..
I just get the feel that this cyl is running rich and the low RPMs just cause the cyl to foul. Is there an adjustment for Mixture on the carb? if so, where is it and is clockwise Rich or Lean?????
Lastly, Am I hurting Cyl 3 by running on the other 2?"
 
"yes, engine that is not runni

"yes, engine that is not running in proper balance, in harmony between cylinders can fail. For the adjustment, look for screws with a spring attached to it, if they don't have them, your carbs do not have mixture adjustment., Very important as Reeves says: check the carb throttles for alignment, they should open and close equally, if one moves 1mm, the others should move 1mm, if not, have linkages checked and related components"
 
"This engine always starts and

"This engine always starts and runs.... Like a champ. It simply drops a cyl about a 1/2 hr in to a trip around the lake.... The question is fuel or electrical? If Fuel, I will look at linkage first... good suggestion. I will also do a compression check, plus check the coil.. I really want to know if I am harming the cyl walls on the cyl that drops out by washing them with unspent gasoline or am I simply passing the fuel out through the exhaust ports, This answer will help me with the fear of harming the engine during trial and error troubleshooting. Thanks Larry"
 
"Well, the unspent fuel will d

"Well, the unspent fuel will do only the lubrication part instead of making combustion and energy transfer you know, but don't worry about the hurting walls or surfaces, it will not happen unless you cut fuel supply to the carb. If you plan to cut fuel in a carb, lubricate the cylinder walls with oil just in case."
 
"Larry, I have heard of others

"Larry, I have heard of others with a similar problem. There have been a few that have had a problem with the powerpack failing when it gets warm.

I'm sure Joe will advise you correctly on the matter - he has a ton of experience....

And I would echo Whaler's comments - as long as a gas/oil mix is getting into the cylinder, despite it not firing, it will provide all the necessary lube so that you do not harm the piston/cylinder.

In fact on some of the newer V6's, only one bank will fire at idle, with the carbs simply providing gas/oil for lube to the other bank - and this is done by design...."
 
"Whaler and Graham Thanks for

"Whaler and Graham Thanks for the advise. I did a compression test and all three Cyl are at 130 psi... Sweet news.... I cut the slow idle mixture a bit to see if that helped... I bought the "Book" and will check out the Coils next... I suspected that the power pack may be the issue all along.... Can you tell me more about issues that exist with the power pack heating up and becoming troublesome?
Thanks for the advise guys... I do appreciate it... Joe Reeves, if you are out there I value your opinion on this as well..."
 
You would simply hook up a tim

You would simply hook up a timing light to the #3 cylinder and observe the flash as you operate and see if the flashing quits after warm-up.
 
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