Hi,
I have a '94 20 hp Evinrude that smokes too much during low rpm/trolling from the upper exhaust & prop that is affecting my health!:% I'm using the recommended 50:1 ratio with the factory evinrude 2 stroke oil, but still get a lot of smoking & black gunk dripping from the lower unit after haul-out...as well as a new ugly black boot stripe on my transom's waterline. I'm happy to hear from previous threads that it is probably not the rings...but I do not know all of the motor's history. The motor jumps around a little bit at idle & is once in a while a tad sluggish out of the blocks, but has a lot of power on the plane. I'm thinking carb tuning, but I'm not too knowledgable. Any ideas or suggestions?
You can get rid of a lot of the smoke by switching to Castrol Full Synthetic TC-W3 outboard oil. Plus, they claim it's bio-degradeable. I made the switch and my 35 smokes hardly at all now. But it does take some running to burn all the present crud out of the exhaust housing before you notice all the improvement. I get the Castrol at WalMart.
Pennzoil, Amzoil, and others have full synthetics. Cabela's has a semi-synthetic that I've run for years. It's getting pricey like the other oils but still cheaper than most. You might do a good decarb job if you are seeing black gunk. Its a sign of carbon build-up and yes, you may be running very rich at low speed. The cheapest fix is to always run upwind. d
I'll try the decarb. Also, I've seen a couple of threads about using 100:1 mix for some Evinrude models. Would I be a total idiot if ran with two tanks: one tank using 50:1 mix for high speed then switching over to a 100:1 tank when trolling?
100:1 worked well in controlled OMC laboratory tests - no excessive wear. BUT it didn't leave enough oil film on the internals to prevent oxidation (rust) during non-use. Plus you're really narrowing your margin for error. So OMC went back to recommending 50:1. Do the decarb. You should not be getting so much smoke as to be a real nuisance using 50:1. OMC wouldn't have sold many engines if they were obnoxious smudgepots, and they sold a lot of engines. I think you're just way sludged up. Do the decarb on a windy day; if you think you've seen smoke before, wait'll that Seafoam starts loosening stuff up in there!
OK...I did a decarb yesterday...three times to be exact. It produced a lot of white smoke. After running it WOT for about a mile, I went fishing...slow trolling. I still had a lot of blue/grey smoke. I also noticed that the tell-tale stream was rather cool. I'm wondering if there is a thermostat in the '94 20hp that is not functioning...thus producing a cold motor and smoke???
I have not switched oil yet, but plan on it after I burn the rest of my premix--about 10 gallons @ $3. I'm also planning on a compression check in the next day or three.
There is a thermostat, the same setup as on my 1984 35hp. To tell the truth, mine doesn't work worth a hoot and I have had it apart to check it. It has a pressure bypass system which must bypass all the time with a good water pump. Mine never warms up to what I consider it should. But it's been running perfect for 22 years so I'm not going to worry about it. Still has the original spark plugs in it. I do a lot of running at idle up and down the scenic rivers.
Once you switch to the synthetic I think you will see a marked difference. At least I did.
I will join the crowd as they are right on. Do a decarb, then keep Sea Foam in the tank (per recommendations on the can) to keep the symptoms from returning and use full synthetic oil. Pennzoil makes it too and I got mine at wallyworld. Agree that 100:1 doesn't leave you much margin for error and once you clean up your engine and run syn oil you'll be surprised just how smokeless she runs. BTDT with many engines.....latest, yesterday, with my chain saw. Besides that, when you've finished, she runs like a top.
I'll get some seafoam for the tank too. It sounds like everyone highly recommends it.
Anyway, looking back at previous replys there was mention of "running rich." It got me looking at the carburator. I only saw one adjustment screw with a tension spring on the starboard side of the carb. This one was backed out 7 1/2 turns! I do not know if this is my problem...but I've been seen threads of 1 1/2 turns for other motors. Is this how this screw should be set? I do not see any other adjustment screw! I'm I not seeing something?
Nowadays the high speed is fixed so you only have the low speed. I'd back her all the way out and look at the tip insuring that it is a perfect cone. If it has an overtension ring on it it's useless and needs to be replaced.
1 1/4 to 1 1/2 is where most are set for starters. With yours that far out several things could be playing here and one could be leaking gaskets or crud in the carb.
Once you get it inspected and reset, you'll know right away if you have other problems as it should respond to adjustment within 1/4 turn to make the engine run differently.
Hopefully it is just the mixture screw.
But one other possibility is on some motors if the fuel pump diaphram is bad it can leak gas into the motor causing a rich condition.
I've leaned out the carb. I'm out now about 4 turns now. I tried to get to 1 1/2 turns but she wouldn't idle without coughing & sneezing. I took her out for a test drive...including about 2 hours low rpm trolling...and she cleared right up. Little smoke and I can breathe again and ran pretty smooth.
Now, a bigger question. Can a lean carb cause too high of temps? I now notice that my tell tale is now warmer than previously. Too warm?...I'm not sure. What temperature should the tell tale be?? Also, I'm running in cold Puget Sound salt water & I'm still using the 50:1 evinrude oil.
How can I balance smooth engine idle, acceptable 2-stroke smoke output as to not damage my motor, and normal temps???
Thanks for everyone's help. I think that I'm getting closer!
Carb too lean on the high speed system can cause localized internal overheating due to preignition. But the high speed system is fixed and not adjustable and this would only be a problem running at high speed, not idle. Besides, you would have to be mighty sharp to detect it in cooling system temperature before the pistons burn.
I would say that if you are concerned about the temp, especially at idle, you should start with a water pump checkup. I can't relate it to the carburetor.
Not sure, but fairly sure there is. Look for a tan wire disappearing into the cylinder head or block somewhere. That would be the sensor. If you ground that wire with the key turned on, it should sound the alarm.
Too much 2nd Hand Smoke 20hp Evinrude
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