1974 Evinrude 135 fouling plugs

[bash11]

I have a 1974 135 HP Evinrude that fouls plugs in less than a few hours. The fuel pump was replaced and the carbs rebuilt in 2011. The plugs appear wet with gas/oil, but not black. Compression is 147,140,125,140 psi. The engine fouls the recommended plug (UL77V) quickly (within an afternoon). B7HS10 plugs last a little longer. Engine starts normally (both hot and cold) and idles nicely. It misfires when loaded. When the plugs "clear", WOT is normal and smooth. I used to get a whole season with a set of plugs.

All 4 coils have been replaced.

Is this most likely a fuel mixture problem or an ignition problem?

A marine mechanic suggested that I should change the jet sizes (to run leaner). This idea does not make sense to me since I am running it at only 600 feet altitude and have stock jets. Could the engine change so much that jets need to be changed? (The carbureters are fixed jets with no adjustments).

When I rebuilt the carbs, I adjusted the plastic float so it is parallel to the gasket surface when placed up-side-down. The book suggests that I use a gauge to adjust them. How critical is this adjustment? I checked the float valve before putting the bowl on and it seemed to shut the gas off when the float was horizontal. Did I adjust the floats correctly?

Any suggestions?

 

[71Windsor]

Re: 1974 Evinrude 135 fouling plugs

Using a gauge would be the best way to get your carbs set right but sounds to me like that's not your issue. What fuel / oil ratio are you currently using? Also I would pull your plugs and ground them while some one turns over the engine and check the color of your spark. Let us know if your getting a small dim blue or orange spark or a nice bright big spark and the color of it. That will help determine if your having issues with electronics or fuel.

 

[bash11]

Re: 1974 Evinrude 135 fouling plugs

Using a gauge would be the best way to get your carbs set right but sounds to me like that's not your issue. What fuel / oil ratio are you currently using? Also I would pull your plugs and ground them while some one turns over the engine and check the color of your spark. Let us know if your getting a small dim blue or orange spark or a nice bright big spark and the color of it. That will help determine if your having issues with electronics or fuel.

Thanks for the quick reply.

I am using 89 octane fuel with no ethanol (sold at the marina) and OMC branded TCW-3 oil in a 50:1 mix. I installed a water trap in the fuel line last summer and there was no water in it at the end of the season. Last time I checked the spark, it was blue and fat (using the plug). I have not checked to see if it could jump 7/16 inch.

Does anybody know what the specification is for the float gauge 324891? Do you use it with the gasket in place or against the bare metal surface?

 

[airman1094]

Re: 1974 Evinrude 135 fouling plugs

IMO it sounds like its running way too rich! I too live and boat around 800 ft ASL and have had no trouble related to jets! Could the carbs be allowing too much fuel in? Is the fuel consumption same as before or more than normal? Does your motor have a primer on it? Could be stuck open!

 

[boobie]

Re: 1974 Evinrude 135 fouling plugs

Will the spark jump a 7/16" open air gap on a spark tester ?? Is the mtr coming up to proper temp when idling and at wot ??

 

[emdsapmgr]

Re: 1974 Evinrude 135 fouling plugs

Don't change the jets to lean out the mixture. Next thing you know the engine will be starving for fuel - that's when bad things happen. Boobie has a good comment. The single vernatherm (thermostat) could be stuck open, causing it to run cold at idle. Cold-running engines don't get complete combustion.

 

[71Windsor]

Re: 1974 Evinrude 135 fouling plugs

Don't change the jets to lean out the mixture. Next thing you know the engine will be starving for fuel - that's when bad things happen. Boobie has a good comment. The single vernatherm (thermostat) could be stuck open, causing it to run cold at idle. Cold-running engines don't get complete combustion.

^-- agree!

You can get a spark plug gap tester fairly easily at most auto part stores and they will have presets for different gaps but if you get a crisp blue spark I wouldn't think your having issues with it not carrying a strong enough current to the plug. Better safe then sorry and check it though. I would not lean your engine out not enough fuel is not enough oil and your opening a bigger can of worms there. See if can get your hands on a compression tester and see what the cylinders have. If you have bad rings on a piston the fuel and power could be slipping by not giving you a full detonation.

 

[bash11]

Re: 1974 Evinrude 135 fouling plugs

Thanks for the advice. The engine is off the boat now because I replaced the transom this winter. I will try and hook it up enough on the stand to check the spark. I won't be able to check the temperature till I get the boat in the water. I agree that leaning out can be risky.

I tested the compression before the season ended and it measured 147,140,125,140 psi cold.

Which way is better for measuring engine temp? Crayons of Infrared? Where do you measure the temperature?

Any thoughts on the float level adjustment mentioned earlier in the thread?

Bash11

 

[emdsapmgr]

Re: 1974 Evinrude 135 fouling plugs

If you visually check the plugs after it's idled, they will appear dark and oily. Those engines overfuel somewhat at idle. Pretty normal. If you do a WOT throttle chop, then check the plugs-you will problably find that they are light tan in color. That's also normal. I see you've got a cylinder that is borderline in terms of compression. Usually compression on each cyl should be within 10% of each other-your 125 is right on the border. Have you visually looked inside the spark plug hole to see if anything looks unusual? Pulled the head? Use a laser temp gun to measure the cyl head temps. That engine uses a single vernatherm (thermostat). I think they run a few degrees cooler than later dual stat engines. Probably 130-135 when idling-maybe one of the experts knows for sure. Once you get the engine up on plane, the engine gets extra cooling and the temps may go down 15-20 degrees, depending on lakes water temps.

 

[bash11]

Re: 1974 Evinrude 135 fouling plugs

Thanks for the reply.

I was not really concerned with the 125 psi cylinder because I thought that it could be just a measurement error. I was not using a screw in gauge. I will look in the holes with a borescope.

Where on the cylinder head do you measure the temperature?

Where is the location of the single thermosatat? Can it be removed easily?

Sometimes the plugs look dark and oily, sometimes tan and oily, and sometimes they look good (tan and dry).

When the engine acts up, the cylinder(s) will cut in and out (like the ignition is intermittant) It could be a plug fouling then clearing then fouling, etc.. It is hard to tell which one(s) are doing it. Generally the plugs look better on the top two cylinders.

 

[emdsapmgr]

Re: 1974 Evinrude 135 fouling plugs

Once you get the engine fired up and start to check the cyl head temp, move the laser gun around and measure various spots. Go for the spot with the highest temp. Probably right by a spark plug. The vernatherm housing is located on the exhaust adapter, just below the rear exhaust cover. It's the box with the two large hoses going to it. If you can sense that the ignition is acting up, it probably is. You can read up on some ignition troubleshooting tips at this website: cdielectronics.com Just look for the year of your engine. Weak ignition components tend to fail once the engine warms up to normal operting temps. May run fine when cold-just started.

 

[bash11]

Re: 1974 Evinrude 135 fouling plugs

I made some ignition measurements on my motor. The engine was running when I shut it down and winterized last October. Like I mentioned above, it was fouling plugs rapidly. With a spark tester, #1 and #3 jumped 7/16 inch and was nice and blue. #2 and #4 had no spark even at 1/16 inch! Now I know that the boat ran better than that when I put it away. Could something have happened over the winter? Could it be that I was testing it with an engine that was very cold (approx 45F?)
I swapped the coil connections to the pack and all coils were capable of jumping 7/16 inch, so I think the coils are all OK. I wired the coils back to their proper position on the pack. I then swapped the sensor leads (#1-#3 with #2-#4). Now #1 had a good spark for a while then faded a bit. #3 had no spark. #2 had a good spark, and #4 had no spark. If the trigger was bad, I would have expected #1and #3 to be bad and #2 and #4 to be good- which did not happen.

I took the following measurements using an ES530 DVA and an Oscilloscope: Charge coil hooked to the pack - 320 DVA. This seems good but there is a dark goop (that is now somewhat hard) dripping from each coil.

#2-#4 trigger - 7 ohms - .2 Volts with DVA but measured 1.2 Volts peak on the scope.
#1-#3 trigger - 7 ohms - .55 Volts with DVA, but measured 2 Volts peak with the scope

The trigger voltages were the same disconnected from the pack.

It seems that there is more than one problem here. Any suggestions? Is the dark goop a sign of bad things to come? Could these parts act intermittantly? Does the power pack seem OK?

 

[emdsapmgr]

Re: 1974 Evinrude 135 fouling plugs

If you don't have an original factory service manual, I'd check this website: cdielectronics.com. They have some really good ignition troubleshooting information/criteria. Your stator output voltage looks ok, but it sounds as if it's potting is starting to break down. I'm not sure the trigger meets the spec. I think the condeming output is below .3 volts, so #2/4 is low. Compare your findings with the condemning values at the cdi website. The spark plug coils are usually pretty reliable, as you've found.