Black oil in pick up tube and water pump.

[DunbarLtd]

Good morning folks. Yesterday I removed the lower unit to get ready for the summer, replacing impeller and noticed black oil on the inside of the water tube that goes up to the head. Upon inspecting the innards of the leg it appears the water tube can be exposed to exhuast fumes. I am going to assume finding oil at the bottom of the cooling tube and inside the cup (where the tube inserts) of the water pump is normal? It does appear to be combusted fuel and almost black in color. definitely NOT gear oil. I pressure tested the unit before removing the water pump and there are no leaks.

1988 85HP Force 3 cylinder

 

[Nordin]

This is normal, a two stroker do not combust all fuel.
The unburned fuel goes out with the exhaust down the leg and out the exhaust nose under the cavitation plate.

 

[jerryjerry05]

The lower unit has small holes for the drippins to exit the motor.
Make sure they are clear.

 

[DunbarLtd]

The lower unit has small holes for the drippins to exit the motor.
Make sure they are clear.

The holes in the front of the cowling on the bottom that always drains into the splashwell and annoys me...ha? Yes they are clear.

 

[The Force power]

The holes in the front of the cowling on the bottom that always drains into the splashwell and annoys me...ha? Yes they are clear.

Thats not what jerryjerry05 is referring to, he's referring to the holes in the lower-unit just below the cavity-plate (3 or 4 on each side, near front)

 

[DunbarLtd]

Thats not what jerryjerry05 is referring to, he's referring to the holes in the lower-unit just below the cavity-plate (3 or 4 on each side, near front)

Hmm You mean the anti cavitation plate? I have 3 or 4 one inch long skinny holes for intake of water on both sides. Never seen any drains holes for exhaust. Now I will have to go lay on my back and inspect. Even so, there wasnt a massive amount of oil pooled on top of the lower unit when I pulled it. I first noticed the oil in the plastic cup (where the cooling tube sits) on the water pump, then looked at the cooling tube in the mid leg and noticed oil there too. Didnt appear to be up inside the tube just collected near the bottom. The rest of the LU topside looked pretty clean. Ill try to find those tiny holes and see if they are clogged.

To me it seems since the water tube chamber is not isolated and exposed to exhaust fumes on top of a rich running 2 stroker when idling, I may just have some of the unburnt fuel collecting on the water tube and dripping down.

We have quite a long no wake zone so Im sure the thing doesnt burn much oil off in the process. Could be that at the end of the day that excessive unburnt oil is just collecting on the tube and pooling on top of the water pump. I still will try to find those holes, regardless. Thanks for the clarification.

 

[DunbarLtd]

Found the holes. They are clear.

 

[The Force power]

To me it seems since the water tube chamber is not isolated and exposed to exhaust fumes on top of a rich running 2 stroker when idling, I may just have some of the unburnt fuel collecting on the water tube and dripping down.

They are separated(in the lower unit section, when bolted together) the only time I can see oil residue collecting on the P/U-tube would be if the motor was running in a test-tank full of it and sat in for a long period of time (not running) OR the lower crank-seal leaking?

 

[DunbarLtd]

First thing I checked was the lower crank seal. No evidence of oil leak there. Its a small amount of oil built up around the PU tube right where it sits into the water pump. Other than that the area was generally oil free. Like I said I pressure tested the LU before I removed the cover on the water pump and it held pressure just fine so i highly doubt the drive shaft seal is leaking and id know gear oil from the smell. This was black like unburnt fuel mix. I will have to snap a picture next time. For now I wont worry about it. See what it looks like next time i drop the LU. I dont have copious amounts of oil slick behind me on the water also. But its just something strange I noticed. Are we sure the water pickup tube and exhaust are seperated? I wish I took a picture.

 

[Nordin]

Nothing to worry about, it is unburned fuel.
Maybe you carb setting is a little to rich but that is better then to lean.
When idling the two stroker do not burn a lot of the fuel.
If you have a leakage in the lower crank seal you should have bad idling and maybe you should see water intrusion in the bottom cylinder.
But as I can not se and hear you engine working it is hard to give some closer advise.
I think it is just unburned fuel from bad combustion.

 

[DunbarLtd]

Nothing to worry about, it is unburned fuel.
Maybe you carb setting is a little to rich but that is better then to lean.
When idling the two stroker do not burn a lot of the fuel.
If you have a leakage in the lower crank seal you should have bad idling and maybe you should see water intrusion in the bottom cylinder.
But as I can not se and hear you engine working it is hard to give some closer advise.
I think it is just unburned fuel from bad combustion.

I pull the plugs after every outing and so far havent seen evidence of water on plugs. They are definitely oily though. But Ive checked them after 5 minutes of running full power and they do dry up. So yea maybe slightly rich setting on carbs and long wake zone. It definitely sputters after the wake zone heading out to the lake. Then clears up after a couple seconds and runs fine at top speed.

But If I slow down and idle too much it sputters again. All needles are set to one turn out. Ive tried to fine tune them and I cant hear a difference as if they arent doing anything. Like the rpms raising or lowering. Im assuming it should take a tiny bit of adjustment to make a change in idle and it just doesnt. Ive rebuilt and cleaned carbs (adjusted floats to parallel) I dont know how many times. Made SURE idle circuits were clean. Needle tips look sharp.

And have checked compression many times. Even threw a new head gasket on and rechecked torque many times. All is well in that category.

But it definitely idles like crap (not very smooth) and when I put a tach light on it, its inconsistent. When I run it full power no miss whatsoever. And Ive run it 15 miles without a hiccup. So low speed definitely an issue. I mix 50:1.

 

[Nordin]

Okey, then it looks like it is tuned pretty right.
Do not set the air/fuel mixture screw less than 1 turn out from seated.
As these engines has cross flow scavering system and in some moment the intake ports and exhausts ports are open at the same time, some fresh air/fuel mixture will go right through the exhaust, especially at idling.
OMC started to use loop charging system on the 50Hp and larger in 1972-73 I believe the loop charging system are more efficient for the air/fuel mixture than the cross flow.
I think your oil in the leg and lower unit is normal, nothing to worry about.
It is as it is, the design of the engine will give this situation.
One thing that you can do that maybe will decrease this oily issue is to check the screens in the fuel recircual system.
There is a cover at the intake side of the power head looking like a dogbone.
Pull this cover and clean the screens that are under the plate.
If the screens are clogged the engine will idle bad and more fuel will go out the exhaust ports.