backfiring 175hp evin intruder

[93evinrude]

I have not had my motor in the water yet this year but would like to know whether a bad plug can cause an engine to backfire. It is loud like a gunshot, only happens occassionally(4 times to date)and seems to be at the exhaust outlet.<br />It first happened not long after I had put in new plugs and there has be no noticeable change in engine performance.I had decarbed the engine as well about 3 weeks before I changed the plugs and was running fine before and after the decarb. <br />Also,if a bad plug could cause it, would it be noticeable when looking at the condition of the plugs?

 

[angus63]

Re: backfiring 175hp evin intruder

The plug ignites the problem,but doesn't cause it. A badly fouled plug will cause a miss, a stall, low rpms, etc... . When is the last decarb? Flaking carbon deposits sometimes ignite with a pop. Poor sync and linc might cause it also. Switched plug wires?

 

[93evinrude]

Re: backfiring 175hp evin intruder

thank you angus. I had just added the fact that I had decarbed the engine about a month or so b4 the backfire first occurred juat as you were posting. I will definitely check the wires but wouldn't a crossed wire cause a change in performance.

 

[angus63]

Re: backfiring 175hp evin intruder

On a v6, you could run on 4 cyl on the muffs and hardly notice. Until she's pushing the boat around , performance is unknown. The decarb can open up fresh faces of bonded carbon deposits and the jagged ends can break off and give you some poppin' for weeks to come. My guess is it's just carbon. I recommend regular and thorough decarbs at least once a week, or everyday for a week until this stuff breaks up and gets blown out. Better yet, Do a decarb the night before every trip for a while, and be sure to buzz around at WOT for 15 minutes minimum after each decarb. Best yet, pull the heads and physicaaly remove the carbon being careful not to marr the pistons or cyls or mating head surfaces.<br />Good luck and let us know!!

 

[93evinrude]

Re: backfiring 175hp evin intruder

I'll definitely try the decarb a couple more times.<br />If anyone has any other thoughts, please let me know. Hopefully I'll get the boat out on the water within a couple of weeks.<br />Thank you