Seen lots of posts about this but when I run my motor (which I brought back from the dead after 7+ yrs of storage) on muffs, I get gobs and gobs of oil in the exhaust, spraying all of the prop and LU. I've read this is normal but I can't imagine that this much oil is normal...is it possible that the motor just needs to be run some at high speed to "clean it out"?
Just changed lower unit seals and oil among other things. Only other prob I can think of is that the gas/oil mix is a bit rich in oil. Would that contribute to the problem?
You have to believe it. It is normal. Yes, getting it out and running it will clean it out somewhat, but more still comes.
It's time for a short explanation:
All two cycle engines waste a lot of fuel which blows out the exhaust ports. Some are much worse than others, but they all do it. Unless you have a new e-tech, I guess.
In all two cycle engines (again we aren't talking about new e-techs) the fuel and air charge passes through the crankcase on it's way to the cylinders. There has to be room in the crankcase for the crankshaft and connecting rods to whiz around. That means the fuel/air charge slows down as it goes through that big space, especially at low rpms. The slow movement allows droplets of fuel to "rain" out of the charge and settle in the bottom of the crankcase. That settled out stuff would cause lousy running if it were allowed to go on through in liquid form. So what they did on most older engines was drain it off somehow and dump it into the exhaust stream, and ultimately into the lake.
OK, I agree it wasn't too nice, but the truth is the truth. Beginning around the 1970's people started becoming more concerned with the environment and mfrs started devising ways of capturing that wasted fuel and burning it. Also, a side effect of the horsepower race was that the crankcases were made more efficient, thus less "rain".
Yes, newer motors still create an oil slick in the water and spots on the driveway, but nowhere near as bad as the old ones.
Running in a barrel or bucket makes it appear much worse because it is concentrated and emulsified in the water.
Use full synthetic TC-W3 for less smoke and slick on the water and better bio-degadeability if you care.
Edit: Guess I should mention that the oil you put in the gas is not all burned. It wouldn't lubricate the cylinders properly if it did. So, the unburned protion also blows out the exhaust. The burned portion is the smoke, the unburned portion contributes to the slick.
March, Since that is a 1963 motor, you need to either run it on a 24::1 mix as OMC recommends, or consult with an expert to see that it has all roller and needle bearing construction, and run it on a 50::1 mix.
BTW - 24::1 mix is 1 qt TCW-3 oil to 6 gal regular gasoline.
Location: Edmonton Alberta(land of rightwing nuts), Canada
Posts: 1,351
Re: 63 Evinrude Lark 40 hp - oil in exhaust
The 1963 40hp does have the needle bearing on the piston pins, rollers on the connecting rods and rollor or ball bearings on the crankshaft. My service manual shows no difference in clearances between the 1963 and 1964 models. I know my fathers 63 40hp sea horse lived a long life on OMC oil @ 50:1
The reason I don't say to run it on 50:1 is because if you do it and the motor throws a rod, you will say it's my fault. Even though it was going to throw a rod anyway.
So the most I will say is that there is no major difference between a 63 and newer ones. Then YOU decide for yourself what you want to do.
Thanks F_R for the detailed explanation, it sets my mind at ease about the oil situation.
The mix ratio is a bit confusing, lots of conflicting info out there. Sounds like I should be safe on 40:1 which is what I've most often read is the correct mix.
63 Evinrude Lark 40 hp - oil in exhaust
Re: 63 Evinrude Lark 40 hp - oil in exhaust
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