Surging motor at wot

1995 evinrude intruder. I'm back to scratching my head over this one again. This spring this motor would top out at 5500-5700. Now i 'm lucky to reach 5000 rpm. It will run up to 5000 rpm then drop off to 4700, run back up to 5000 then repeat the process. I'd say thats a surge. #4 Plug looks kind of like its running lean. Not as tan as the other plugs and #6 Gets dirty or looks like it might be burning a little rich. Well i've took the carb off of #4 and went through all the jets with a thin peice of wire. I didn't find anything in there anyway. Checked float height. Its right at one inch drop to the bottom of the float which is within the speck. This motor has also killed two starting battery's in two years. Might just be coincidence. I did a rectifier test 12.6 not running and 13.25 at fast idle. Voltage guage reads 14 volts at higher speeds, is that normal? Seems like its charging the battery or at least the systems working. I do have another optical eye trigger i could try but i don't know. I know its not a fuel problem before the fuel pump,took the vent hose completely off inspected for anything in it, nothing. So that only leaves carbs, but i've been through them all a few times now. Carbs or spark but which one? All my ignition components are less than a year old. It is cdi stuff though. I never get accurate readings doing ohm tests on anything. So i might just have to take it on to the dealer.

Re: Surging motor at wot

Charging is fine ... nothing wrong there.

Sounds like a weak coil or something else affecting only one cylinder. Have you done a spark test with an adjustable gap tester ... should get a clean, blue spark over ~1/2" gap on all cylinders? This may be more challenging, though, BC it sounds like it's somewhat intermittent. Powerpack is likely fine, since it would normally affect more than on cylinder. Carb problems usually don't cause surging.

I would start by checking for good spark in all cylinders, then go on from there.

Re: Surging motor at wot

Alright got the adjustable spark gap tester. I must say its the best $7.50 i ever spent. Anyways 1, 3, 5, 2 all have a clean blue consistant 1/2 gap spark. #4 and #6 however do not. The spark starts out strong when you start the motor then it gets noticeably weaker... then it gets erractic, not consistant like # 1,3,5,2. I just bought a new powerpack last year looks like i'll be buying another one. Anyone think it could be stator? Thats less than a year old too. I did find some loose magnet fragments under the flywheel when i removed it the other day. All CDI stuff. I wish you could still get original omc stuff. I've heard the cdi stuff is junk and now i'm starting to believe it. The wierd thing is this is the same two cylinders i was having problems out of when i changed packs last time. Compression checks out fine on both cylinders and nothing about how the plugs are reading suggests i check it again for the umpteenth time. I believe cranking my motor repeatedly during compression testing helped kill that battery anyway. So i've had this motor take out two battery's and now what is likely two different powerpacks. all though the first one that was on it was the original. Open for suggestions before i eat the cost of another powerpack

Re: Surging motor at wot

I would consider finding a dealer with a coil tester and have the two on the cylinders in question checked. Unless there is a problem with the stator or timer base, it's unusual for powerpacks to not last. They just don't fail that often. BTW, CDI has an excellent reputation and I've personally had good results with their products.

CDI has an excellent troubleshooting guide, which is a free download from their website (it's under the "downloads" section). I would suggest downloading and using it, before spending any money. Good luck.

Re: Surging motor at wot

Well wilde1j you were right. If you're familiar with how these ignition systems are setup you know that they stack one coil on top of the other. Well, i had a guy start the motor while i watched the spark gap tester and noticed one of the spark plug wires bleeding off onto one of the grounding tabs on the top coil. So i start investigating them all and noticed on the bottom two coils, the ones i've been having trouble with arch marks on those tabs on both sides. Simple fix really... i just pulled the wires out from under those coils and shifted them forward. Motor sounds and idles different now. I haven't dropped it in the water yet. I suspect at higher rpms and more voltage if you were to remove that protective cover back there you would have had quite a light show. Anyway thanks for the help and i'll get it on the lake before the week is out and post back on the results. I don't think i'm going to put that cover back on there as it pushes those wires toward those grounding tabs. Forget that, thanks again.

Re: Surging motor at wot

Glad you're running right again. Enjoy. You may want that download anyway. It a good piece.