Yamaha 150 - oil leak - The Hull Truth

Peltz · 07-29-2009, 02:01 PM

I have a 2004 Yamaha 150 2 stroke. I noticed an oil leak the other day and would like help finding the source of the leak. It is a 2 stroke so there is no motor oil. The oil that is leaking is not the same color as the 2 stroke oil I put in the oil tank. It is an amber color like normal automotive motor oil and thicker than 2 stroke oil. The leak is minor - no puddles or anything, just residue that has leaked down the outside of the motor. The motor is stored in the full down position (vertical).

I have inspected the oil tank, all of the lines and hoses that transport oil and the oil pump and have not noticed any leaks. I removed the collar (see photo) and it looked like the leak is coming from around the drive shaft or shift rod area. (I think that is the area). The red marks on the photo indicate where the oil is leaking. What oil would be around the top of the drive shaft? I noticed in the schematics that there are several oil seals and o-rings. Does gear oil get pumped up that far? The motor runs fine and I have not noticed any performance issues. I changed the gear oil last week and it appeared normal - not milky. The tilt and trim work normally also.

Can anyone help? Is this a crisis such that I shouldn't use the boat until it is fixed or can I wait and fix it later in the season? I don't want to miss the last half of summer while my boat sits in a repair yard, but I also don't want to create a bigger problem. Thanks

A1 Outboard · 07-30-2009, 05:47 AM

Gearcase lube is contained in gearcase by seals under the water pump. The seals on the bottom of the crank around the driveshaft are mainly to keep water out of the splines. The splines are only lubed by what ever is placed on the splines when the gearcase is installed. Oil leaking from the bottom of the powerhead normally is darker than the two stroke oil used in the engine and will have a gasoline smell. Gearlube will have a sulphur smell. It seems that you could continue to cautiously continue to run the engine listening for unusual noises and monitoring oil consumption.

Peltz · 07-30-2009, 07:13 AM

Thanks for the reply.
What would cause oil to leak from the bottom of the powerhead? Would it be a bad gasket perhaps?
Could something like this cause a powerhead failure? I assume that there is still lubrication.
Is that a major repair in terms of time and expense?

I would say the smell is more gasoline than sulphur. Maybe the color lightens as the leak runs because it is not dark. I did notice that the oil tank was low last time out, but I was not sure if it was increased oil consumption or just that I had not filled the oil tank lately. I absolutely plan on having this looked at by the Yamaha tech but am wondering if this is urgent or if it can wait a few weeks. Thanks

A1 Outboard · 08-03-2009, 03:52 PM

Any time you have a problem that involves the engine oiling system you run the risk of powerhead damage. The oil can be leaking from a number of places at the bottom of the powerhead. Finding the source of the leak may require removal of the powerhead to locate the source.