30 hp Evinrude problem

My 30 hp, 2 stroke Evinrude starts up and runs fine. After I get to my spot and troll, it still runs and starts fine. However, if I've been trolling for any length of time, when I try to move on at full throttle, it misses like crazy and won't go more than about 1/3 throttle. Sometimes, after it cools down, it will run OK at full throttle again. I've had the carb checked, new fuel filter, new plugs, changed tanks, hoses and gas. No change. I've had it to two mechanics for a total of 5 or 6 visits and they can't seem to figure it out. This has been happening every outing since last August. Any suggestions?

I have a 30 and it is sensitive to the vent on the tank being open .

Sounds like carb issues still to me. Take has end of hose (engine side) and pump gas in jar and inspect it. Sometimes gas is dirty or has water in it. If its clean then I would suspect jets in carb dirty again. Easy to fix with can or carb cleaner after removing carb from motor. Those motors are relatively easy to figure out. Also get you a services manual as it will pay for itself the first time you work on motor yourself and not take to a mechanic.

sound like a plug is fouling . when running at low speed you are not burning the oil off git a hotter plug or try another tank for troling use less oil in the mix .what plug are you using ? some come with the serface plug and don`t have the gap . try a QL77JC4 . if it self mixes it could be injecting to much oil .another thought to check is to carry extry plugs and change when it does it that will tell you if it is the plugs fouling .

Brand of oil may make a world of difference, get boats in all the time with won't run, idle right, I look them over then look for oil bottles. You'll be suprised how many people use , and will post here that any oil is fine, I recomend a good 2 stroke oil with a motor manufactors name on it. Wally world , and the other general purpose 2 stroke oils don't burn off as well and they are blended for general use, weed eater, outboard etc. Problem is outboards run around 140 degrees and a weed eater, well grab the head on that one when running hard and you'll have a bunch of ugly scar's you can tell your grandkids about. Only other thing I can think might be heat soak, motor super heats after shutting it off and all the gas in the crankcase evaporates, and ethenol can cause this problem and the higher the octane the higher the ethenol. Maybe a new thermostat , and water pump may help and if you change the pump , DON'T forget to change the rubber grommet in the top of the water pump housing.

Always use OMC TC3 oil. I had some problems with generic outboard oil many, many years ago, so I've steered away from it. In a pinch I will use Mercury or Pennsoil outboard oil, but haven't had to do that for 4-5 years.

Another possibility is the power pack. After running a while you could have a component(s) breaking down after getting heated up. Once it cools off it is OK until it heats up again. I have ran into this with other electronics and 1 power pack. Components in older electronics doing this could be isolated by using a can of freeze. FREEZE SPRAY, 10 OZ CAN | AllElectronics.com I don't know if this would work on a power pack or not but it would be cheaper to try than buying a new power pack. When it starts to act up spray the pack thoroughly with this stuff then immediately try running the motor.

It could be the powerpack heating up, but loading up the cylinders during trolling and fouling plugs is a super common problem. OMC suggested in the 50's that you use J4C's for lots of high speed boating, and J6C's for trolling (one heat range up) to prevent fouling---just an example.
I would do as suggested and carry an extra set of plugs and try them when it gives you trouble after trolling. If that solves the problem, you have your answer---step up 1 heat range up on your plugs when trolling. IF they're black/wet/sooty after trolling, then the rich mixture at low speed is the trouble. A spark plug in a 2-stroke that has the correct mixture should have a tan color after a high speed run of a few seconds, and have a chocolate brown color after a few minutes of low speed trolling.
JBJ

Man some great advice on here from these guys

Back in my 2-stroke motorcycle days (God I miss those days) I learned to never use a "sand blast" plug cleaner. It eats the glaze off the porcelain of the plug and they soak up oil like a sponge afterwards.


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