Notice of Fuel Slick, Exhaust?

[99yam40]

If a two stroke is idling for some time, particularly when it is also a richer mixture of fuel and air and fuel and oil, oil stays in the exhaust, particularly if it is cold.
Now if the piston and piston rings are wearing the fuel oil tends to also stay in the crankcase thru blow by pressures. Similar to the oil found wandering up the spark plug thread (how does it get there?) Discounting a fuel leak from the carby's, which would produce a lot of smoke on startup, this oil " hanging around" has bypassed being burnt.

The slick needs to be analysed, to determine whether it is fuel, two stroke oil or gear oil. The amount needs to be determined. I recall Chemistry where a tiny drop of this oil, produced a film several square yards: we were to calculate the size of the molecule!

Not suggesting replacement of the exhaust cooling plates, but this a long term maintenance thing anyway. The oil escaping into the cooling water only needs to be a tiny amount. We need a better picture for us to form an opinion what the sick is.

The 2 stokes I have seen have re-circulation lines with check valves to pull the pooled oil out of the bottom of each section of crankcase and put it back in to be burned. If bad they could let oil pool up until it has to go somewhere.
I found 3 out of the 4 on my little C40 were bad back when I replaced my crank.
I wonder if that could also cause problems for Jason.
On my motor I had oil running down the drive shaft .
I had a bad lower crank seal also.

there was also talk about tilting a 4 stroke motor up a little after turning it off to make sure oil drained away from cylinder heads as it cooled .
but I would think a 2 stroke should not have enough oil on the cylinder walls to worry about.

[zenoahphobic]

Agreed...

It's a two stroke, no oil pump (like a 4 stroke at the bottom of the engine near the crankcase) to leak.

Each "lower end" for each cylinder is sealed.

Per Jason, the engine runs fine, negating the lowest cylinder (if leaking ), pumping fuel/oil into the water..

If a two stroke is idling for some time, particularly when it is also a richer mixture of fuel and air and fuel and oil, oil stays in the exhaust, particularly if it is cold.
Now if the piston and piston rings are wearing the fuel oil tends to also stay in the crankcase thru blow by pressures. Similar to the oil found wandering up the spark plug thread (how does it get there?) Discounting a fuel leak from the carby's, which would produce a lot of smoke on startup, this oil " hanging around" has bypassed being burnt.

The slick needs to be analysed, to determine whether it is fuel, two stroke oil or gear oil. The amount needs to be determined. I recall Chemistry where a tiny drop of this oil, produced a film several square yards: we were to calculate the size of the molecule!

Not suggesting replacement of the exhaust cooling plates, but this a long term maintenance thing anyway. The oil escaping into the cooling water only needs to be a tiny amount. We need a better picture for us to form an opinion what the sick is.

[pstephens46]

Man you area hard case....lol But funny.

I think based on past posts Jason and I are somewhat alike. I like to take things apart just to look. Guns for example. The firing pin on a Glock pistolhas little springs of course. There is a little gate that slides down to expose the parts. Nobody told me how far those things fly when freed by sliding that little part down. All I wanted to do is look at the damn firing pin.

[panasonic]

At the boat ramp there always seems to be a fuel/oil slick hanging around. I've noticed a slick around my engine at the ramp, but never this much and never this obvious the slick is coming from my engine. Can't say I could tell the difference between the look of a fuel slick and gear oil slick. Do you? Is pressure testing the gear box the best way to go about checking the integrity of the prop shaft seal?

Jason...if it where my engine I would start simple. Take the prop off,inspect for oil at the prop shaft seal, clean the prop shaft seal area, maybe you got some fishing line in there...who knows. Grab the the shaft and see if you got any slop in the shaft. Leave it a few days and see if it leaks.

If that is not the problem, then do the pressure test as Scott suggested.

[panasonic]

Careful Zeno. You may send Jason over the brink with ideas like that. He gets that idea in his head and that motor will be spread all over the garage.

Man you area hard case....lol But funny.

[TownsendsFJR1300]

I am trying to figure out where this supposed corrosion hole/leak could form to allow oil to leak into the water.
Not sure where a bunch of oil would be held in the exhaust to leak into the cooling water circulated in the motor

Agreed...

It's a two stroke, no oil pump (like a 4 stroke at the bottom of the engine near the crankcase) to leak.

Each "lower end" for each cylinder is sealed.

Per Jason, the engine runs fine, negating the lowest cylinder (if leaking ), pumping fuel/oil into the water..

[99yam40]

I am trying to figure out where this supposed corrosion hole/leak could form to allow oil to leak into the water.
Not sure where a bunch of oil would be held in the exhaust to leak into the cooling water circulated in the motor

[pstephens46]

I would not rule out corrosion between the exhaust and water jacket leaving a tiny hole allowing overnight oil trickle through.
With heat the oily residue mixes better with the water.
I know it all ends into the water, but the extra heat may explain the appearance.

Careful Zeno. You may send Jason over the brink with ideas like that. He gets that idea in his head and that motor will be spread all over the garage.

[zenoahphobic]

I would not rule out corrosion between the exhaust and water jacket leaving a tiny hole allowing overnight oil trickle through.
With heat the oily residue mixes better with the water.
I know it all ends into the water, but the extra heat may explain the appearance.

[TownsendsFJR1300]

Changed the gear oil about a month ago. No water and no discoloration of old oil.

Plus 1 on the above posts.

If you use a very clean "catch" container, or better yet, use your original filler pump threaded end and hose, you can drain direct into the original quart container and re-use the oil..

Might take awhile using the hose but as long as everything else is spotless, you should be good... Pour your container full of your month old oil, BACK INTO the quart, and simply re-pump into the LU. This also gives you a chance to inspect for any metal, water.

[DennisG01]

Towards the bottom of instructions, under "Note"....what's the check hole and why does it need to be covered when removing tester?

I believe it's referring to the hole that the tester is screwed into. As Stephens said, it's in case there was any pressure still in the gear case when the tool is removed.

[pstephens46]

Darn. And I just replaced the gear oil. Thanks for the service instructions. Towards the bottom of instructions, under "Note"....what's the check hole and why does it need to be covered when removing tester?

Residual pressure? Who knows? They default to the safe mode as in "remove prop before removing lower unit". I now do that to save 12 lbs of heft.

[Jason2tpa]

But... it's not about your engine being healthy or not. It's that ALL 2-strokes do what you are seeing. It's the nature of the beast. It's quite possible that the water conditions and sunlight conditions were such that it made the slick more noticeable. And, maybe it's been there before but you just weren't looking? Plus, think about what happens when you start up a cold engine... gotta prime it, right? That usually means a little extra fuel. The spark plug condition (color, etc) will tell more than just spark - it will tell HOW that cylinder is burning... meaning it's not just an "all or nothing" thing. If all look good and consistent, then it reassures you that everything is firing properly and could be chasing a non-existent issue.

This next comment does not negate gear oil leaking out, but do you have any water in the gear oil?

Changed the gear oil about a month ago. No water and no discoloration of old oil.

[Jason2tpa]

(No oil in the LU when checking)..

Darn. And I just replaced the gear oil. Thanks for the service instructions. Towards the bottom of instructions, under "Note"....what's the check hole and why does it need to be covered when removing tester?

[DennisG01]

But... it's not about your engine being healthy or not. It's that ALL 2-strokes do what you are seeing. It's the nature of the beast. It's quite possible that the water conditions and sunlight conditions were such that it made the slick more noticeable. And, maybe it's been there before but you just weren't looking? Plus, think about what happens when you start up a cold engine... gotta prime it, right? That usually means a little extra fuel. The spark plug condition (color, etc) will tell more than just spark - it will tell HOW that cylinder is burning... meaning it's not just an "all or nothing" thing. If all look good and consistent, then it reassures you that everything is firing properly and could be chasing a non-existent issue.

This next comment does not negate gear oil leaking out, but do you have any water in the gear oil?