18 hp Small lower unit oil leak

[Chuck Gibson]

I have a 1992 NS18C2 that seams to have a very small oil leak from the lower unit. It actually seems as if it is coming from the water intake on the starboard side of the engine. Is this even possible? Can this be repaired?
Thanks for any help you can give me!
Chuck

 

[pvanv]

If it's black and smelly, it's unburned fuel/oil mix, and is normal. When you drain/change the LU lube, is it cloudy or clear?

 

[Sea Rider]

Could be leaking through lower oil drain screw too if with a bad gasket.

Happy Boating

 

[Chuck Gibson]

When I drained the oil it was clear. There was a little bit of water that drained out at first, by little I mean maybe 1/4 teaspoon. I always turn the gas off at the tank and run the motor until it stops while it is on the trailer in the lake just before pulling it out of the water. Could this still be unburned fuel? Maybe it is the oily residue draining down...

 

[Sea Rider]

If smelly and taffy with dark color is combustion left over which is normal being a 2 strokes OB, if clear specially after having changed gear oil, there's a lower leg leak, will need to change all lower gaskets and oil seals, comes in a kit.

Happy Boating

 

[Chuck Gibson]

I am beginning to think this may be the problem. Does that kit have a specific name? If I have to tear into it I guess I will also change the impeller while I am in there. Is there a procedure written out to perform this repair?
Thank you much!

 

[Sea Rider]

Both are available as complete kits :

Water pump repair kit : 362873220 Standard
362652310 Chrome plated (lasts longer)
Lowe unit gasket set : 398873210

Check Iboats or any Tohatsu dealer for them, check if codes are correct, sometimes are changed.

Check Youtube vids for water pump and gasket repairs.

Happy Boating

 

[Chuck Gibson]

Thank you so much. The leak is extreamly small but I believe it is leaking out of the water intake. I will be out of town for the next couple of days but I have left the motor clean so I can make sure of my leak when I return. I will keep you posted.
Thanks again!
Chuck

 

[Chuck Gibson]

Found it. The oil is coming out of the two small openings at the front of the motor directly below the cavitation plate. Each of these holes are at the rear of small slots starting at the leading edge of the motor. What are these holes for? Will the lower unit gasket set you recommended take care of this?
Thanks again,
Chuck

 

[Sea Rider]

Chuck,

Those are small round water drains, will see water outing from there when OB is flushed with muffs, anything including unburned fuel leftovers could be draining from them. Probably you are mixing too much oil, 50:1 is the recommended.

Happy Boating

 

[Chuck Gibson]

Excellant. Seeing that I just changed the oil in the lower unit and the oil draining out of the holes is clean and clear, I will order the kits you recommended and get back with the results.
Thanks!
Chuck

 

[Sea Rider]

Chuck,

Are these the leg holes to which you are referring ?





This is a Tohatsu 18 HP model 18E2, assume your lower leg is same. Won't see "clear gear oil" coming out of upper hole. Remove prop and confirm there's an gear oil leak through prop exhaust or through lower water drain, If confirmed so, need a lower leg kit. Might as well do the complete water pump kit if in need to do so.

Happy Boating

 

[Chuck Gibson]

I hope this photo transfer works... Here is where the oil is coming from...

 

[Sea Rider]

Chuck,

Both are bit different lower legs due to model, anyway it's a water drain, impossible to be draining new gear oil from there, to me it's combustion left overs if sticky and gummy. Let's hope for Paul to chime in for his tech veredict.

Are you using correct fuel/2 strokes 50:1 mixture ?

Happy Boating

 

[Chuck Gibson]

To the best of my knowledge I am using the correct mixture. I have owned this boat/motor for two years and have never noticed this problem. The boat has been parked under a storage shed and has only been taken out once this year and that was about three months ago. I noticed a puddle of clean oil under the lower unit and that is when I started trying to figure it out. It was sitting with the motor raised at that time. I will lower the motor to see if the leak amount changes. The only thing I have done since noticing the leak was to drain the remaining oil and replace with clean oil.

 

[Sea Rider]

Sitting engine while raised could make combustion leftovers to drain from lower hole, check while engine sits vertical.

Happy Boating

 

[Chuck Gibson]

After lowering the engine it has all but stopped. The oil that was leaking out was clean and clear. I ordered the lower seal kit as well as the water pump kit and it should be here next week.

 

[Chuck Gibson]

Sitting engine while raised could make combustion leftovers to drain from lower hole, check while engine sits vertical.

Happy Boating

The odd thing is that the engine has been sitting in that raised position for a long time without leaking. I wonder if the hot Texas weather caused it to build pu pressure or something...

 

[Sea Rider]

Chuck,

If it's new clear gear oil draining down , definitely you have a lower leg oil seal issue.

Happy Boating