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1974 Evinrude 15 sluggish running on single cylinder

G

gnshowzaolcom

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"I have an Evinrude 15 hp on a

"I have an Evinrude 15 hp on a 14' sea nymph. Motor runs inconsistently...sometimes great, at other times chugs and pushes boat along slowly and can't throttle up. Or, does not start at all. Seems to run on one cylinder. Both plugs spark. At times when running poorly motor will sputter a few times and then takes off...running strong. Or, it will run strong to fishing location. Then, when I start it to move, won't run. I had it serviced three times. Carburator cleaned and serviced. New plugs, points, coils, plug wires, condenser, etc. Runs well in service tank. Then, when I get to the lake, doesn't run. Is something shaking loose in trailering? Any ideas? My service guy gave up and told me to sell it but I don't want to pass problems to someone else. Thanks!

Vic"
 
"You don't say what spark

"You don't say what spark plugs you're using. What are they?

That engine requires Champion UL81J plugs, gapped at .030 . Anything else will give you intermitent operation."
 
"Hello, and thanks for your re

"Hello, and thanks for your response. Plugs are Autolite 4092. I checked and this should be an equivalent plug to the Champion you specified."
 
Hello...

I just received a

Hello...

I just received a 1974 15hp service manual I purchased. It identified the proper plug as Champion UL4J and not UL81J

Are these equivalent?
 
"The latest information I have

"The latest information I have is that these motors are supposed to use champion UL81C.

http://www.boatsetup.com/SparkPlugChart.html

I have a 1975 9.9Hp motor which is the identical motor except for the carburetor. I had pretty much the same problem you are experiencing. In a test tank the motor worked well (keep in mind that without a load on the motor, it is difficult to even notice if only one cylinder is firing). As soon as I got it on a boat the motor would surge, then bog down, then surge again. I did a lot of diagnostic tests and determined that my ignition system was providing excellent spark, my compression was fine. I then decided to change the spark plugs from the UL81Cs to some NGK B7HS I had (these are UL81C equivalents). The problem went away. I then put in a totally new pair of UL81Cs and the problem was right back again.

The end of this story is that I put back in my NGKs and have never had that problem again. I have heard that the 1974 to 1976 9.9/15Hp Evinrude gave OMC a real headache with their ignition systems. Anyway, mine works fine now. I have no idea about the autolites. Sounds to me they are closer to the champions then the NGKs."
 
Yes.

I should add that I ha

Yes.

I should add that I have used Champion plugs in other outboard motors with no problem at all. So I am not trying to say that Champion makes bad sparks plugs. All I know is my 1975 9.9Hp Evinrude really does not like them.
 
"Just out of curiosity, are yo

"Just out of curiosity, are you remembering to open the vent on the tank each time you use the motor? Check your fuel system good."
 
"Hello, and thanks for the tip

"Hello, and thanks for the tips. I changed the sparkplugs to NGKs, changed the gas tank (with a new fitting), and put on a larger diameter gas line and different primer bulb. Motor started like a charm and ran great (in the tank). Real life test in a day or two. Unfortunately, as I changed three (or 4 or 5)things at once, I am not really certain what helped. Keep your fingers crossed for me and thanks for the help!

Regards,

Vic"
 
I really appreciate the info.

I really appreciate the info. IK had the boat out yesterday and today...ran great (until I hit the log). No harm done tho. Thanks for the help. I'll pass this along to my service guy. Thanks again!

Vic
 
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