Lower unit oil leak

[pdonatto]

I have a Nissan 6hp 4 stroke motor circa 2006. A few days ago I noticed an oil sheen on the water. After removing the motor from the water I noticed oil below the motor. Today I drained and replaced the lower unit oil, the old oil was milky/thin and I suspect water intrusion. After filling the lower unit with new oil I noticed new oil dripping from the lower unit. Upon closer inspection the oil was coming out a small hole. This small hole is 1 inch forward and 1/4 inch below the upper oil plug and is about 1/8 inch in diameter. This small hole also appears to be machined and not corrosion. What is this small hole and how do I prevent oil coming out and water getting into the lower unit?

 

[pvanv]

Re: Lower unit oil leak

That hole is a water drain for the cooling system. If you are seeing oil there, you have a leak... possibly a lower unit driveshaft seal or cam rod o-ring that is allowing oil into the cooling system. OR...

Just as common is a leak of crankcase oil. The 2 different oils smell different, so you should be able to identify whether it's actually leaking from the LU, or coming from above. If it's motor oil, you may be over filled, or the motor may have been laid on the wrong side, allowing oil into the driveshaft housing... if so, it can continue to drip for several days.

I would drop the LU and inspect it, since you have confirmed water intrusion due to the milky appearance of the drained oil. If you have compressed air available, you can pressurize the LU to about 5 psi, and may find the leak more easily that way. Probably time to install a seal kit regardless, since you definitely had water inside the LU.

 

[pdonatto]

Re: Lower unit oil leak

I'm 99% sure it's lower unit oil. I checked the crank case oil level and it was normal. The crank case oil is new and still honey colored. However, with the motor in the tilted up position and the drain hole facing upward, no oil leaks out. When rotated so that the drain hole is facing downward, oil immediately flows from the drain hole and stops as soon as the motor is rotated back. The leaked oil is more greenish than honey colored. And lastly, it smells like the oil in the lower unit oil tube.

If you concur, it appears to me that I have a bad seal or o-ring. I'm currently out of the country and don't think I can get spare parts. Are there any temporary repairs that would last one month until I get to Hawaii and not do any more harm to the lower unit?

 

[pvanv]

Re: Lower unit oil leak

Yes, sounds like it's gear oil. BTW, the motor oil level should not get too full. Keep it between the lines on the dip stick.

If you need to live with the leak for a month, use the very best LU lube you can get. Some of the synthetics claim that they can operate with 50% water for a while without damage. Change the LU lube frequently if you can (to get the bad stuff out), and run the motor frequently (daily?) in both F and R to reduce rusting.

Once in a civilized port, get a seal kit and a wp kit, drop the LU, and inspect it to see if you can isolate the leak. As long as the case isn't cracked or corroded, you should be able to get it re-sealed. Be sure to do the 2 o-rings of the cam rod bushing... they are often overlooked. That's also the time to replace the wp kit, while the LU is down.

 

[ruipimenta]

Re: Lower unit oil leak

Hello (Im portuguese and my written english is not the best), I have a 2 stroke 70 hp tohatsu TLDI (2003) with the same problem I think.
It has a leak of oil just from a hole just close to the lower oil plug. I?m would like to have some help to solve the problem. The oil is black!

 

[pvanv]

Re: Lower unit oil leak

This is a different issue on a different model, and should be in a new, different post. That aside... Probably unburned fuel/oil mix, which is normal. Does the fluid smell burned? Is the oil in the LU clear?

 

[ruipimenta]

Re: Lower unit oil leak

I have not inspected the lower unit oil.
Do you think that is not a leak from the cranck case seal?
The oil is dark and seems to smell burned.

 

[pvanv]

Re: Lower unit oil leak

Based on your description, the residue is normal for a 2-stroke. If the motor is running properly, there would be no reason to suspect bad seals.

 

[ruipimenta]

Re: Lower unit oil leak

Nice to know
The motor apparently is fine, but I have the feeling that maybe is spending more oil then it should.
I think is a 1:50 proportion, but seems to be consuming more than this
Should I monitorize the consumpt of oil?

 

[TOHATSU GURU]

Re: Lower unit oil leak

Yes, you should.