[framarjen]

I have a 1985 Evinrude 120 V4. It has been recently rebuilt. Since I purchased it, the lower starboard cylinder never fired properly. I performed a compression test with my daughter before buying it, and performed it again. Both times, it is within specs. 135-140 all cylinders. I suspected bad carboration and fuel. The fuel has been completely cleaned with proper filters and I'm currently running 89 OCT. The VRO pump has been disconnected so I'm running 50-1 mix. The carboraters have been completely cleaned with no change in the cylinder. I have even installed more carboraters, with no change. I have also interchanged with another cylinder. The spark is hot and blue, it has a new power pack. I tested the coils, which are fine. I even interchanged coils to the bad cylinder, which still had no effect. A couple of weeks ago, the porcelain insulator on the inside of the spark plug was broken. It did not break off, but slid back and forth on the metal electrode. The cylinder seems to fire above 2000 RPMs. All the spark plugs look nice and clean and firing properly. I have even interchanged the spark plugs. What's going on? Is there some damage inside the engine? All answers appreciated. Thank you.

[wilde1j]

How do you know the engine is misfiring? Plug w/ moving insulator belongs in the garbage. Have you tried pulling plug wires off one at a time to see if there is an RPM drop? Drop indicates firing, no drop means cylinder isn't firing. Have you tried spraying premix in each carb? RPM increase means that cylinder is fuel starved. Tell us what's happening!By the way, don't waste your money on anything other than 87 octane fuel. Just get more deposits and engine doesn't need it.Compression is fine.

[Trent]

Intermittent firing on one or more cylinders: Can be caused by low voltage from the stator of a bad timer base. DVA test stator and timer base. Disconnect the rectifier and retest. If the problem disappears, replace the rectifier. If it doesn't replace the pack.

[framarjen]

Thanks wilde one. I performed the drop test. Every good part i use does not change the rpm of this cylinder. I will spray50\1 and see what happens.I am sure the intake of fuel is ok .Is thre something internal like reed valves? By the way i have replaced all the plugs with a hotter one and they all look great

[framarjen]

Thanks trent I will perform the stator test.However this problem is not intermitent. This one cylindre does not fire until over 2000 rpms

[FreeBeeTony]

I have what sounds like a very similar problem. Trent, can you elaborate on this DVA test?Thanks

[Dhadley]

Be very careful about "hotter" spark plugs with todays fuel. Especially if you are using something other than 87 octane. And be sure to stick with Champions on E/J's.You mentioned the motor was rebuilt. If it was rebuilt before you bought it and has always done this, you may want to verify that the piston is not in upside down.BTW - I'm sure you know since you have been through the carbs so much, but just a reminder - the lower starboard cylinder is fed by the lower port carb. Good luck!

[FreeBeeTony]

DHadley, Can you shed any light on this DVA test?

[BKool68]

What RPM's are you reaching? Have you tried running with the hood off? I had a problem with the bottom wires grounding out to my motor latches.