Oxygen Sensor question for the OX66 folks

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SBH2OMan

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Location
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As many of you know, I've been trying to chase down some demons in this motor, and have replaced/repaired/tuned just about everything on board (new fuel filters throughout, sync & link, TPS adjust, new plugs, tested and gone through all electrical, replaced fuel pump resistor, new LP fuel pumps, etc etc etc.)

After finding an earwig in the fuel line inlet to the filter separator (!), I think I have the final rough performance issues narrowed down to O2 sensor related performance. The problems/questions are two-fold:

1. I can clean the dip tube and sensor, but after running for 5 or 10 hours, it will be completely fouled (clogged solid) again. In fact when I pulled it the other day to inspect it, it was soaked in wet oil and had hard carbon deposits that I had to drill out (by hand) with a small twist drill. I had cleaned it thoroughly maybe 10 hour before (and it had been REALLY bad then).

2. When freshly cleaned, I'm getting the right looking voltage readings, but off by a decimal point... I have my meter set to 20 vdc, and instead of reading around 0.05 volts (5 millivolts) and varying between 0.02 and 0.09, it i reading around 0.5 and ranging from 0.20 up to around 0.80 while underway (under load). Also, when I cover the #1 throttle opening, I don't see a dramatic change in the reading at idle. It goes from maybe 0.55 to 0.70 and then gradually back to 0.55 or 0.60 and when I uncover it, it basically does the opposite. I was under the impression that the change should be more dramatic.

I am using Yamalube 2M oil. I am using Ring Free with every tank. Oil rod has been adjusted and oil burn is "normal" (she's burning about 1 gal of oil per roughly 30 to 35 gallons of fuel). Plugs are the right heat range. I have run a couple of gallons of Pennzoil Premium Plus (semi synthetic) but I've never heard anything but positive results from people using the same oil on their Ox66 motors.

1. Any ideas on why the dip tube would be fouling so badly? Faulty heater in the Oxygen sensor?

2. What's up with the voltage readings? Unless I'm crazy, "millivolts" on a 20VDC scale should read as 0.05 (that would be "five millivolts") which is what the spec says. Why on earth would the Oxygen sensor be developing 10x the voltage? Or is the spec wrong? The volt meter functions normally otherwise. (IOT, when I bridge the battery it doesn't say "123.5 volts")

Thanks in advance for the suggestions.
 
I'm no expert on these things (I generally leave maintenance like this to my mechanic who I trust more than my skills), but I would suspect two things:
1. Faulty O2 sensor
and
2. Carbon fowling of the top-end due to item #1

If it were mine, I'd replace the O2 sensor and clean out the top end with a de-carbon session, using one of the many methods already published here.
 
SBH2OMan":3czaz5hk said:
...oil burn is "normal" (she's burning about 1 gal of oil per roughly 30 to 35 gallons of fuel).
That OB should burn 1-gallon of oil to every 50+ gallons of fuel. I wonder if you have an air leak somewhere, which is fooling the motor into thinking it needs more oil. IMHO it is that 'extra' oil that is all that goop and hard cabon you are needing to drill out. If your present mechanic thinks 1-gal oil to 30-gal fuel is 'OK' ... me thinks you need a new mechanic!

SBH2OMan":3czaz5hk said:
What's up with the voltage readings? Unless I'm crazy, "millivolts" on a 20VDC scale should read as 0.05 (that would be "five millivolts") which is what the spec says. Why on earth would the Oxygen sensor be developing 10x the voltage? Or is the spec wrong?

In the article attached by Bill Grannis on servicing the OX66 O2 sensor, he states that values between "0.1 and 0.9 volts DC" are typical.
 

Attachments

  • Yamaha O2 Sensor.pdf
    369.5 KB
Interesting. I guess the official Yamaha Service Bulletin I'm using for reference (#099-008) is wrong when they say "0.2 to 0.9 millivolts, a normal reading is 0.3 to 0.6 millivolts"

So it looks like my readings are "normal" and within the range, but it doesn't explain the fouling. Hmm...

I got my oil consumption numbers from some informal polls of people on the iBoats and "Yamaha outboard parts" forums. I think the Ox66 motors are a lot more thirsty on oil than the HPDI motors and other direct-injection 2-strokes. I'd love to be wrong, though, cause that oil gets expensive.

Oh, and FWIW, I don't have a mechanic that knows this motor. Its why I've been forced to become an expert. I've had three different mechanics work on it, and every time I've actually had to end up "getting it right" myself afterwards.
 
Didn't take note of the oil consumption in your first post, but Dale is correct.
Normally, these motors run at around 50:1
 
Megabyte":g2bn9mps said:
Didn't take note of the oil consumption in your first post, but Dale is correct.
Normally, these motors run at around 50:1

Hmm, sounds like I might be mis-informed. I've followed the oil control rod adjustment specs to a "tee" but seems to be one of those things that is a pretty sloppy adjustment (you have to go a full turn of the plastic clip, so its never "perfect" plus there is so much slop in the linkage that the Heisenburg Principle seems to really apply. If anyone has a nifty tip for getting it to 50:1, I'm all ears... (by the way, I can't remember if turning the plastic clip clockwise onto the threads increases or decreases the oil ratio - anyone know?)

bryan":g2bn9mps said:
Can the heater part of the sensor be checked that it is getting enough current to reach the operating temp?

I checked the voltage across the white wires (the ones that supply the voltage to the heating element) and they show the alternator output voltage (12v to 14v) so unless the heater in the sensor itself is bad, I don't think this is the problem.

It seems like the issue has more to do with the over-oiling than with a bad sensor, since I am getting readings that are in=spec for the O2 sensor. I am tempted to try that $37 Bosch universal sensor, though - I just don't want to carve up the plastic housing if I can avoid it...
 
Brent":2fr85i49 said:
thanks

Where did you read the Bosch was the equivalent to Yamaha sensor?
There are a number of posts that you can find via Google search. According to the pictures I have seen of the Bosch unit and the notes I've read on other forums, the top portion of the sensor is larger diameter, so the black box & rubber boot that goes over the top of the Yamaha unit won't fit properly. People have used header wrap or spark plug "heat socks" to keep heat away from the inside of the engine cowl. I'm not crazy about hacking up the plastic housing for the O2 sensor, but saving $250 is a heck of an incentive to do so...

http://forums.iboats.com/showthread.php?t=377018
 
I'm not crazy about spending extra dough either, but I'm also not crazy about cobbling up something that may not work... or last.
I would buy the real deal from SIM if it were me.
 
Brent":vmj47llt said:
ok thanks
m2cw
I would buy a Yamaha part. If it works it will last for years

Yea, I hear ya, but I've spent sooooo much damned money on this motor, my wallet is getting fatigued. I'll bet I've dumped $1,000 just in parts (probably more) over the last 6 months, plus another $2,000 or $4,000 on labor for mechanics that didn't know what they were doing with this motor...

Take a look at the Yamaha one:
9-32101_2.jpg


Compared to this NTK 25569 ($75):
NTK20501519_ngk_25569_pri_larg.jpg


Located at this web site
http://shop.advanceautoparts.com/1/1/53 ... 25569.html

FWIW, that NTK one looks more like the one in my hand right now from my Ox66 than the "official" replacement unit from Yamaha does... The one in my hands right now that came off my motor, has those "half moon" holes in the tip rather than the oval ones.

This NTK one might be the way to avoid the housing modification required by the Bosch unit.

FWIW, I think there are only two or three manufacturers of Oxygen sensors - NTK, Denso, and Bosch.

I'm going to a FLAPS and see if I can lay my hands on the NTK unit and compare side-by-side. I'll bet they're a match... :D
 
SBH2OMan":2w9cznca said:
2. When freshly cleaned, I'm getting the right looking voltage readings, but off by a decimal point... I have my meter set to 20 vdc, and instead of reading around 0.05 volts (5 millivolts) and varying between 0.02 and 0.09, it i reading around 0.5 and ranging from 0.20 up to around 0.80 while underway (under load). Also, when I cover the #1 throttle opening, I don't see a dramatic change in the reading at idle. It goes from maybe 0.55 to 0.70 and then gradually back to 0.55 or 0.60 and when I uncover it, it basically does the opposite. I was under the impression that the change should be more dramatic.

2. What's up with the voltage readings? Unless I'm crazy, "millivolts" on a 20VDC scale should read as 0.05 (that would be "five millivolts") which is what the spec says. Why on earth would the Oxygen sensor be developing 10x the voltage? Or is the spec wrong? The volt meter functions normally otherwise. (IOT, when I bridge the battery it doesn't say "123.5 volts")

Thanks in advance for the suggestions.

Two things..

1) 0.05 is not five millivolts.. it is 50 millivolts. .005 is 5 millivolts.

2) The correct voltage spec is 0 - 1V. The voltage swing you are looking for is typically in the .3 - .8V range.. That is volts, not millivolts, and if you are setting your MM to 20V DC it should read .3 - .8V.

From the readings you posted, it appears that your O2 density sensor is actually producing the correct output voltages. From my experience, the cleaner the sensor the more rapid the voltage swings.

If your sensor is getting that gunked up after 10 hours, then something probably isn't working correctly.

Hope this helps..

-- Tom
 
Thanks Tom. Yea, I figured out that the Yamaha bulletin is actually wrong when it specifies millivolts. It really should read "volts". Got that one figured out. Thanks

I've come to the conclusion that I have two problems:

1. A marginally functioning Oxygen sensor - it is a pre-update version, so I'm guessing its original. It has been soo gummed up so many times that I'm going to just replace it in order to eliminate the possibility of it being a contributing factor.

2. Over-oiling based on either leaky oil pump seals or control rod adjustment. I'm going to re-check the oil rod adjustment and pay careful attention to the plastic linkage up on which it rests at the upper end for "slop" that might be causing over oiling despite the fact that I've adjusted it to spec several times (and replaced the rod and both end clips and jamb nut

I figure #2 is causing #1..
 
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