Evinrude E-NATION, for those dedicated to water, power, fishing and fun
Posts: 1
Registered: ‎07-31-2016

fouling plugs

 i have a 2015 ranger z521 with a e250lhoaba fouled a plug last fall so a tech replaced it with a new one, all went well, now this weekend i lost all power again, pulled plugs today and they are all black and very carboned up. bad enough that i will need to replace them all. the lake i mainly fish is a no wake so engine hrs are mostly under 1200 rpm. dont have any lakes close to go out and run like it wants to run, usually only on vacation do we get to a place big enough for that. anyway is there something i need to do or am i just going to have to get used to plugs fouling on this unit.

Posts: 6,906
Registered: ‎07-14-2011

Re: fouling plugs



Plug fouling is often a sign that the motor is not developing enough heat in the combustion chamber. Ofen this is due to too much fuel delivered, weak ignition, or the engine not reaching the correct operating temperature.


Sparkplugs in a direct fuel injected engine of any make are black and sooty looking when running at low speeds. That is normal, of course deposit buildups can occur depending on conditions and how the motor is set up.


What is your top rpm and speed at full throttle when you are trimmed up for best speed?


When you are running at the normal slow speed, is the motor deep in the water as the bow is high? If so, there may be excessive backpressure in the exhaust that could also contribute to fouling. Try trimming the motor up more to be sure the exhaust relief hole is above the waterline.


Ask you technician to check the temperature sensors on the engine to be certain that they read the air temperature while the motor is cold.  The engine temperature of both cylinderheads have to be withing specs also for good low speed operation.


Your tech can also contact the Evinrude dealer support team for assistance in correcting the plug fouling problem.




"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 



The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.