Tohatsu gear oil leak

[CAPTAIN FANTASTIC]

My 5 year old Tohatsu 6hp 4 stroke outboard has developed an oil leak seeping through the propeller, which indicates that the seal by the prop shaft is leaking, hence need replacement. The engine has done in total no more than 80 hours since new.

However, the manual does not mention anything about a seal or oil leaking through the propeller.

Have you had this problem? did you have to replace a seal, how?

 

[VicS]

Are you sure that it is gear oil? Does it smell like gear oil and is it as viscous as gear oil?

If gear oil is leaking out water will very likely be leaking in and the oil in the gearcase will show signs of water ingress.

But yes there is a seal on the propeller shaft. You will have to remove the prop and the bearing & seal housing to change it.

Parts diagrams at http://www.tohatsuoutboardparts.com/Parts-Books.html

 

[CAPTAIN FANTASTIC]

Are you sure that it is gear oil? Does it smell like gear oil and is it as viscous as gear oil?

If gear oil is leaking out water will very likely be leaking in and the oil in the gearcase will show signs of water ingress.

But yes there is a seal on the propeller shaft. You will have to remove the prop and the bearing & seal housing to change it.

Parts diagrams at http://www.tohatsuoutboardparts.com/Parts-Books.html

You may be right, it may not be gear oil, may be engine oil. However, the engine has not been on its side and with only 80 hours on the clock I would not expect any engine head problems. It is difficult to tell whether the oil is engine or gear oil.

 

[salinia]

I once owned a 5HP 4 stroke Mariner same sort of design engine I think. It developed an oil leak and the red light came on I found out it had a corroded hole here is a pic:

Hope you don't have that problem all the best.

BTW this engine was only 3 years old and it did spend a lot of its time living in the cabin on its side.

 

[VicS]

You may be right, it may not be gear oil, may be engine oil. However, the engine has not been on its side and with only 80 hours on the clock I would not expect any engine head problems. It is difficult to tell whether the oil is engine or gear oil.

Gear oil usually stinks! It will if it's the usual EP type of oil.

 

[VicS]

Quite apart from the possibility of a corroded hole there are several seals and gaskets around the bottom of the oil pan that could leak engine oil.

Important to determine if its engine oil or gear oil before going any further.

 

[hacienda]

I once owned a 5HP 4 stroke Mariner same sort of design engine I think. It developed an oil leak and the red light came on I found out it had a corroded hole here is a pic:

Hope you don't have that problem all the best.

BTW this engine was only 3 years old and it did spend a lot of its time living in the cabin on its side.

Hi all,
after some googling, I found this thread.

I have a 2005 Mercury 6hp which have developed a more and more severe oil leak over the last 2 months. Without a doubt it is the engine oil that's leaking; the oil level in the pan drops fast... I have yet to take things apart to find the exact source of the leak, but undoubtedly the oil comes from somewhere around the oil pan. The oil seems to be leaking out regardless of the storing position (standing up against the wall or lying down on the correct side, tiller handle down).

Salinia, was it easy to remove the power head (engine) in one piece from the casing like you've done in the picture showing the corroded hole? Have you attempted any repairs since the posting?

All the best, happy yachting

 

[hacienda]

Having disassembled the power head, the oil pan shows exactly the same corroded hole as in your motor, salinia.

A new oil pan is around 235 USD... so now I'm considering methods to repair the corroded oil pan. Maybe welding is an idea. Or some chemical compound...

This is an old and perhaps dead thread, but I'll keep you posted anyway

 

[hacienda]

Managed to disasseble and clean oil pan and all associated parts. Cleaned around the corroded hole with spirits to get rid of all oil residue, and also heated the area for a few seconds to possibly get rid of any oil soaked into the porous "walls" of the corroded hole. Then I applied a chemical metal compound (the one that you mix together metal powder and fluid stuff). Reassembled the motor with a new set of gaskets, refilled 4-stroke oil and now it runs without any signs of leak. Hopefully this did the job, but time will tell...

 

[GrahamM376]

My 5 year old Tohatsu 6hp 4 stroke outboard has developed an oil leak ............... The engine has done in total no more than 80 hours since new.

Why not phone Tohatsu UK for advice, I've found them very helpful. At that age, there shouldn't be any leaks.

 

[CAPTAIN FANTASTIC]

The original post is over 5 years old. The engine is still alive and kicking and there was no further leaks, it was one off after long standing upright some oil leaked from the gear.

"Hacienda" It is interesting to see how you fixed the leak with a bit of luck, your engine will go on for years.

 

[hdshutt]

Hey I know it's a VERY old post. But I have a tohatsu 5hp model no. MFS5BS. It was sitting on it's side for a VERY long time. I don't think you can even set these down on it's side, must be upright. So obviously oil was everywhere. I started it up and burned most the oil out of the motor, ordered a jet for the carb to make it a 6hp and when I get it I plan to clean the carb fully. Before I dissassembled the lower unit it was already leaking oil from the propeller and when running would bring oil to the top of a 5 gallon bucket of water. I haven't ran it much so when I did disassemble it and fix some things (like the water pump cover was cracked, got a new one and impeller) and put it back together it would run with no signs off leak. Once I put it in a bucket after about 5-10 mins you can see a good amount of oil around the surface of the water in the bucket. Not sure if it's just old oil from it sitting or not. Wanted to ask hacienda what compound you used for the hole if you can remember?

If it doesn't stop I'm going to take it apart from the top and see if I have a hole that you guys. Thanks.

Managed to disasseble and clean oil pan and all associated parts. Cleaned around the corroded hole with spirits to get rid of all oil residue, and also heated the area for a few seconds to possibly get rid of any oil soaked into the porous "walls" of the corroded hole. Then I applied a chemical metal compound (the one that you mix together metal powder and fluid stuff). Reassembled the motor with a new set of gaskets, refilled 4-stroke oil and now it runs without any signs of leak. Hopefully this did the job, but time will tell...

 

[VicS]

Hey I know it's a VERY old post. But I have a tohatsu 5hp model no. MFS5BS. It was sitting on it's side for a VERY long time. I don't think you can even set these down on it's side, must be upright. So obviously oil was everywhere. I started it up and burned most the oil out of the motor, ordered a jet for the carb to make it a 6hp and when I get it I plan to clean the carb fully. Before I dissassembled the lower unit it was already leaking oil from the propeller and when running would bring oil to the top of a 5 gallon bucket of water. I haven't ran it much so when I did disassemble it and fix some things (like the water pump cover was cracked, got a new one and impeller) and put it back together it would run with no signs off leak. Once I put it in a bucket after about 5-10 mins you can see a good amount of oil around the surface of the water in the bucket. Not sure if it's just old oil from it sitting or not. Wanted to ask hacienda what compound you used for the hole if you can remember?

If it doesn't stop I'm going to take it apart from the top and see if I have a hole that you guys. Thanks.

From the owners manual