18hp Lower Unit oil leak

[bonz_d]

Can't seem to figure this one out.

Oil is leaking out of the exhaust and drain holes but water is not getting in. This oil leaking out is milky like one would see inside the lower unit but the oil in the LU is clean and clear.

I pulled the unit this morning and there was some milky oil around the water pump but not inside it. The oil level was also low.
Pulled the prop also and tried to pressure test it in a tub of water but didn't see any signs of air bubbles.

There had been another lower unit on this motor that was leaking oil like this also, only worse and I know the shift rod seal was shot in that one but I don't think there would be that much residuals left.

Any thoughts or suggestions before I reassemble this and check it again?

 

[Sea18Horse]

Re: 18hp Lower Unit oil leak

So what does the milky sludge smell like? Does it smell like 90wt or does it smell like two stroke exhaust. 90wt is distinctive. If there's even a little bit in there you can smell it. I wouldn't be surprised to see milky goo around the exhaust. I see it all the time in my test barrel. More so when the weather is cool. But on mine it smells clearly of two stroke oil exhaust.

I wouldn't normally think it likely that lu lube can leak out without at least some water getting in. But anything is possible I guess. The fact that it's low is curious however. Did you check the level in the exact same position it was in when you filled it? Good luck!

Cheers...................Todd

 

[bonz_d]

Re: 18hp Lower Unit oil leak

Thanks Todd,

No this isn't 2 stroke exhaust oil, much to thick and too much of it. This stuff was running down the drain holes at the top of the LU and the bottom of the exhaust creating a small puddle after we pulled the boat from the water.

Yes, I checked the oil level on the boat with the motor down in both cases.

 

[F_R]

Re: 18hp Lower Unit oil leak

So, according to your own words, there was milky oil around the water pump, but not in it. How do you figure gear oil got clear up there, high above the highest seal and in the exhaust and cooling water flow?

It isn't gear oil.

What you are seeing is emulsified motor oil that has gone through the engine and done it's job. Some of the oil that you put in the gas is burned (smoke) and the rest goes right through the engine and out the exhaust where it is mixed with spent cooling water. Some of it then goes out the various drain holes and worries the owner to death. All two-strokes (except E-tech) do it to some degree and some are much worse than others. If it is running too rich or misfiring, it will be worse also. Depending on the year of your 18, most of them deliberatly dump raw fuel and oil into the exhaust....considerable amounts of raw fuel and oil! There is no practical way to prevent it. OK, so it isn't "green". But that's another arguement.

 

[bonz_d]

Re: 18hp Lower Unit oil leak

OK then. Plan is to put it in the water tomorrow. If I see it like this again I'll post pictures. Have been running a 9.5hp Johnson for about 20 years and never seen this much white milky oil drain out after use.

Thanks again, Kevin

 

[bonz_d]

Re: 18hp Lower Unit oil leak

Hi again,
Just got back from the water and when I pulled it out there was still some white fluid draining from the drain holes though nowhere near as much as before. I took a couple pictures but they didn't turn out very well.

So if this isn't gear oil, which I'm starting to believe you all, is this because of an over rich mixture or something else?

This carb has a fixed high speed jet and when I reassembled the carb I set the low speed per the directions in the package. Which was "Seat needle all the way closed then open one turn".

Seem to run good at this setting but smokes a bit for awhile at start up then clears up like my 9.5 does. Still haven't had a chance to run it above a high idle because of the "No Wake" restriction.

 

[bonz_d]

Re: 18hp Lower Unit oil leak

One more update and a big thanks to those that helped.

Ran it again today and was finally able to open'er up. Had one big cough when I started to throttle it down and it quit. Don't know what that was all about but it started right back up and didn't do it again.

No milky oil this time when I removed it from the water! All I do know is this 14' Lund S DXL is very fast with an 18hp on it and only me in the boat. Would hate to see it with a 35hp that it's rated for!

Think now it's time for a Seafoam treatment and new plugs.