Leaking 02 sensor yam 250 0x 66

[Whalure]

Had motors serviced last month, and they ran great. Second or third time boat was out after being serviced, cleaned and put on trailer I noticed black oil dripping down motor. First thought was exaust, but pulled cowling, and leak is coming from 02 sensor box, unscrewed 02 box and oil poured out.

What could be causing this? Gasket left off when serviced? Sensor not reinstalled properly? Or another issue. Any help would be great.

 

[rodbolt]

Re: Leaking 02 sensor yam 250 0x 66

post the model number and has the powerhead ever been replaced?
there is a specific reason for my question and the need for a full model number.
but I think I know what happened anyway

 

[Whalure]

Re: Leaking 02 sensor yam 250 0x 66

Its either a SX250txry or a LX250txry, its the port motor and they are counter rotating. And yes the power head has been replaced on that motor where the 02 sensor is leaking. I think it was done by Shallote marine in NC. You seem to really know your stuff. Thanks for your help.

The primary ID #S are 61ax 104545 and 61bx 102438

 

[Whalure]

Re: Leaking 02 sensor yam 250 0x 66

Forgot to ask if this leak would cause a rich or lean condition?

 

[Whalure]

Re: Leaking 02 sensor yam 250 0x 66

Anyone have an idea what happened? Taking to shop in morning and wanted to make sure they dont overlook my acutal problem, or what could be causing the problem. Thanks

 

[rodbolt]

Re: Leaking 02 sensor yam 250 0x 66

whats most likly happened is an untrained or illiterate tech got ya, in mid 03 the 3.1L block changed nessesitating a change to the O2 sensor holder and attaching gaskets, if the tech looked up the part number by the pre mid 03 number and not the post they most likly put in the wrong sealing parts.
happens.
especially to those that dont pay attention nor read tech bullitens.
post the part number of the gasket kits they used and when was that powerhead replaced?
if the put the wrong stuff on it dont let them charge you again as the kits are pricey.
but most likly they used the Y model gaskets on a mid 03 and up block.
I have seen it before.
the Y indicates they are 2000 models.

 

[Whalure]

Re: Leaking 02 sensor yam 250 0x 66

The powehead was replaced in spring 07, it was a brand new powerhead from yamaha not a reman. By looking at my stb motor the gaskets are different, when you unbolt the 10mm bolts that hold the 02 sensor. The motor with the new powerhead, has a square gasket, while the stb motor gasket is square but is diecut the where if forms around the lip of the left side of the bracket.

Do you think I damaged motor in any way? I will point out the kit numbers in the morning. Guess this would cause the sensor to get dirty more than usual with all that oil.

Thanks so much for your help.

 

[rodbolt]

Re: Leaking 02 sensor yam 250 0x 66

most likly now you will need to replace all the contaminated insulating materiel in the sensor cover. the outer gasket stayed the same, the draw tube stuff all changed, mid 03 and older used a gasket,mid 03 and later used an oring and a gasket in the correct order.
have them show you the tech bulliten.
if the foam insulation in the cover is contaminated it will cause the sensor to give the ECU inccorect readings.
if the sensor tells the ECU its runnig over rich the ECU will lean out fuel and damage is possible above 4000 RPM.
there are 3 tech bullitens out on testing the O2 sensor output after cleaning, you may ask to see them as well. they are on both parts smart as well as the dealers YDS.
just make sure you get a detailed list of parts used and what procedure was done and sensor output voltages.
then post them.

 

[Whalure]

Re: Leaking 02 sensor yam 250 0x 66

Rodbolt,

Mechanic said it was probably the oil control mechanisim when I dropped it off. I handed him your post to my reply, and he is going to call yamaha and review tech bullitens. Have not heard back yet as to what problem is but I think you nailed it. Doubt he would have even thought to check the gaskets, as he said he has replaced a couple of oil controls in the last few weeks.

Thanks for your help. I owe you a cold one or fishing trip.