QD 19 Johnson, excess oil and fuel in water

[greg-o]

Hello for the second time everyone.

I have a question on a 1958 Johnson QD 19, 10HP motor. I have had this motor for a year. Over last winter I sealed the bottom end, replaced the water pump, and a general tune up. When I have it on my boat, it runs and idles great. But when at trolling speed, there is a pretty heavy oil and gas slick behind the boat. I also have a QD18, and there is no gas oil slick with that motor. I do not see any leaks in the fuel system. Where is the gas and oil coming from?

Thanks for sharing your knowledge.

[Mumbles]

Low compression or being out of tune will cause incomplete burning of the fuel mix. Too high of a float level in the carb can let too much fuel go thru the motor to.

How does the QD 18 troll for long periods of time? The crankcase drain may be plugged in it and clear in the QD 19. The drain dumps excess fuel straight into the exhaust housing and will leave a slick behind the boat after idling for a while.

[greg-o]

The 18 does great trolling. As far as the 19 Compression feels strong, but I have not checked it. It will leave an oil slick from the get go. Don’t notice it at speed, but that is because of covering a greater distance. I will check the drain as well as the float level, and while I am at it the compression just for curiosity sake. Thanks for the suggestions.

[Doug Wilson]

would guess float level to high, never noticed that with my QD19

Doug

how is it motors multiply when the garage lights get
turned off?

[frankr]

Let’s start by realizing where the stuff is coming from. Every morsel of oil that you put in the gas goes through the engine. Some of it burns (smoke), and the rest goes out the exhaust–into the water. That is just the way it is, in any two-stroke motor. So why more in one motor than another can be several causes.

Incomplete combustion would have to be #1. Is it set too rich? Are both running the same mix, including same brand of oil?

Crankcase drains were mentioned. I believe both of those motors have the same drain systems. They drain off the fuel that settles out of the fuel/air charge as it passes through the crankcase. That drainage goes directly to the lake, without passing through the cylinders. Again, that is just the way it is. But one may be producing more drainage than the other one, for some reason that I don’t know.

Neither of those have the thermostat-controlled cooling system that came out later, so that isn’t it. Nevertheless, do they seem to be running about the same temperature?

Finally, the exhaust housing was changed between the 1957 and 1958 model years. That brings up an interesting thought. Does one get rid of the stuff by heat or wash-down differently than the other? For sure, it does, but how significant might that be? Something to wonder about

[greg-o]

I am using the same fuel for both, 24:1. I buy Super Tech outboard motor oil from Walmart. I found it smoked less the Pennsoil, and about half the cost. I am very fussy about getting the fuel mix set for the best performance at idle and WOT. I hate a 2 cycle that is 4 stroking because of a rich mix. I might check the float level. Frank R, you raise some interesting questions.

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