2006 25ESH Yamaha outboard is running rough and popping from the exhaust

[campdog12]

I removed the carbs and cleaned them very well, I gapped and changed the spark plugs. I put fresh fuel. The coils seem to have fire at all times. The engine will start and on idle it runs very rough, also when I speed up the engine it still runs rough, but also there is a miss or popping noise out of the exhaust. This started happening all at once. It ran good before, and the last time I went out with it, I started having these problems. It sounds like the engine is back firing or something like that. I would greatly appreciate it if someone can help me with this issue. Thank you.

[99yam40]

You can test compression,spark,timing and fuel pressure, but it sounds like you need to pull and clean the carbs better and then adjust like the manual states

[campdog12]

Thanks for the reply. I will definately try to clean the carbs again. Could the C.D.I. assmebly (powerpack) or the coils cause this type of problem also?

[99yam40]

like i said test what you can first just to prove those things are not the problem

[campdog12]

Thanks for your input on the matter. I really appreciate your help. Compression seems good (~120psi on cylinders 1 and 2), timing is good, coils throw a good arc. Turns out the problem was the air adjust jet on the carbs. I took the carbs apart again and soaked them in cleaning fluid, blew out all of the jets in the carbs and cleaned them very well. I added new fuel with a fuel mix ratio of 100:1, which is recommend by the owners manual. I installed the carbs back onto the engine and set the air jets until it ran smoothly. There is no longer any popping from the engine and the engine runs great. However, at high rpms, the engine has a small surge. I removed the carbs once again, verified that all the jets and everything in the carbs were clean and set correctly. I also checked for vacuum leaks on the fuel filters, fuel hoses, and fuel tank. I changed the spark plugs and ran it again to test it, but the small surge still exists at high rpms (3/4 throttle and up). I have a friend that has a Yamaha 25ESH like mind, it runs very good and doesn't have a surge at full throttle, it really runs good. I took the carbs from his engine and put it on mind and went run it. After all that, It still has that surge at full throttle as it did with the other crabs. So now I can rule out the crabs, because after that I put the crabs back onto his engine and went run it and ren great with no surge what so ever. Any ideas what would cause this issue? Thanks