Looking for guidance please

[Krsowles]

I have an 1997 Evinrude 9.9 4 stroke kicker that runs great for about 10-20 minutes and then starts to sputter and pop like timing is off. So far, I’ve tried pumping fuel and/or choking it and neither helped at all, maybe made worse. Pulled carb apart to look at and it was very clean so just blew it out and reassembled. No difference. Replace coil with another one from different motor and no improvement. I’m at the end of my mechanical skills and hoping people far more knowledgeable can point me in the direction I should continue looking. It does seem to cool down and start and run well again after about 30 minutes but really doesn’t help much for fishing. Thank you in advance!

 

[saltchuckmatt]

I have an 1997 Evinrude 9.9 4 stroke kicker that runs great for about 10-20 minutes and then starts to sputter and pop like timing is off. So far, I’ve tried pumping fuel and/or choking it and neither helped at all, maybe made worse. Pulled carb apart to look at and it was very clean so just blew it out and reassembled. No difference. Replace coil with another one from different motor and no improvement. I’m at the end of my mechanical skills and hoping people far more knowledgeable can point me in the direction I should continue looking. It does seem to cool down and start and run well again after about 30 minutes but really doesn’t help much for fishing. Thank you in advance!

You were correct to pull apart the carb because more time than not people store them with gas and the varnish up. It could be running hot from a bad cooling pump and vapor locking but who knows. Was the engine stored for awhile? Was water coming out of the pee hole? If not that, start with compression, then spark then fuel. Pretty much one of those things.

 

[Krsowles]

Thank you for your reply! The motor only sits over winter. As soon as the ice leaves, it’s used 3-5 times a week. Full disclosure; it’s a 17.5 aluminum fish and ski boat and the 9.9 is the only motor on the boat. Most of my fishing is very close to my mooring and my wife and I live to just putter around the lake. We can trailer it if we want to fish another part of the lake (Champlain) or other lakes. Anyways, it’s used a lot. It has not overheated and the impeller is changed every other season and the tube is peeing great. I believe the fuel and spark are good and worried about compression but haven’t checked it yet. Can compression drop when motor warms up? Would it stumble and pop like bad timing with low compression? Thanks again.

 

[Chris1956]

Gee, I would suspect the ign is failing at it warms up. You might check spark quality, when she starts to sputter.

 

[Krsowles]

I swapped in a good coil and no improvement. Can you suggest what else I might check on ignition? I’m sorry, my ignorance is showing

 

[racerone]

Check valve clearance.------Check compression ( throttle open ) ----The powerpack ( big $$$ ) has an optical sensor.-----Does spark jump a gap of 3/8" on both leads ?-----Perhaps oil pressure switch is acting up ?

 

[Krsowles]

I will check these things as soon as I can, thank you for suggestions!

 

[Krsowles]

A quick update for some closure. I forgot to check compression but replaced the ignition module and stator under the flywheel with parts from my parts motor. I did that because when I put a spark plug tester in line to ignition coil, spark was very intermittent when condition started. After I had done that, I actually bought a technicians manual for that motor. It was used (nearly new) on EBay and it showed me things I could only imagine before! I now see why everyone who knows anything says to make that the first step. Live and learn…
Anyways, took boat out for a 30 min spin because I’ve been wanting to try it but too busy and it ran really well. I’ll get it out this week for (hopefully) much longer shakedown this week and possibly a few fish? Thank you all again for your input and assistance, cheers!

 

[tphoyt]

Thanks for stopping in and letting every know how it turned out. That’s always a big help to others reading through the post.
Glad you had success.
Best