What I've learned so far about the "big block" OX66 motor

Based on another thread, I've decided to post my learnings so far about the OX66 motor on the Lori-K so that it might benefit other Parker owners with similar engines (or those considering buying a Parker with one of these motors). This is in no particular order, and I'll probably update it as I learn more about the motor. I will reference sources where possible. If sources are excluded, you can assume that the learning is from my own first-hand experience. I have a lot of experience wrenching on automotive and motorcycle engines (including complete rebuilds), but this is my first foray into outboard engines...

First, if I was considering buying a boat with one of these motors, I would do the following:

1. Disregard hours on the clock unless excessively high (over 1000) or low (under a few hundred). If well maintained, these seem to have a very good reputation for longevity.

2. Compression check. Don't worry if "low" (high 90's) unless the rest are in the 120's. As long as they are all close (10%) you are golden. According to a certified Master Yamaha Technician, "typicaly the 3.1,especially units produced after 2003, run about 85 PSI on a compression test but Yamaha does NOT post any specifications for compression."

3. Check idle speed. When warm should be 700 to 800 (730 +/- 30 RPM according to my manual). I idling at 1100 you have a problem with a sensor and the engine going into "fault mode" where it locks timing at 7degrees BTDC and idle at 1100. Check WOT - results can indicate the type of sensor problem

4. If you can buy or borrow them, get a "winky blinky" test lamp for reading the fault codes, also get a test harness for testing the TPS and O2 sensor. According to same certified Master Tech:

"no codes no faults.
the exception is the O2 sensor which has NO codes associated with it.
when cold,below about 113*F, that motor will idle about 1100-1200 RPM.
code 33 will be flashing.
once warm the RPM will drop to the designated idle speed and code 1 will be displayed if everything is happy.
if the CTS [coolant temp sensor] fails or becomes unplugged the system will set code 13 unless its an in range failure.
lets say the CTS is ALWAYS telling the ECU [electronic control unit] that the engine is at 90*F.
guess what that ******* ECU is gonna do.
its gonna fix fuel rich at low speed,fix idle timing at 7* BTDC.
idle speed will remain about 1100 RPM and top speed CAN be reached.
unplug the Knock sensor or the TPS [throttle position sensor].
stupid ECU is gonna lock ign timing at 7* BTDC,fix fuel rich and idle speed will be about 1100 and top speed CANNOT be reached."

Click to expand...

These test procedures are outlined in section 8 (electrical) of the Yamaha service manual.

I paid a certified Yamaha mechanic to inspect he engine, he charged me $300 and didn't do any of these simple things other than the comp test. I learned these simple things AFTER buying and wrenching on this motor.

When I trialed the boat, I noticed the high idle, and unfortunately just believed the broker when he said "its a simple adjustment - just a couple of screws". As it turns out, it is a very important indicator of other problems - probably easy to fix, but problems nonetheless.

Procedures for testing and cleaning the O2 sensor (a critical component of this engine - probably THE most critical one):
http://www.boatsetup.com/O2sensor.pdf

If the Oxygen density sensor is giving faulty readings, it will tell the fuel system to lean or richen the mixture and it can lead to disastrous consequences.

Other things:

1. Changing out the Low Pressure Fuel Pumps is within the capabilities of any person that knows how to operate a socket wrench. It only requires a 10mm socket. The only trick is that you need to loosen the high pressure fuel pump assembly to get to one of the bolts on the middle pump (there are three).

2. If you have a 1999 OX66 in a 225 or 250 (and perhaps others) specifically an S250TXRX - BE CAREFUL about which VST filter and gasket you purchase. I recommend pulling opening up the VST tank and inspecting it before ordering, because 1/2 of the parts guides (including the one at SIM Yamaha) are WRONG and you will get the incorrect parts. The proper one for my motor is the 66k series part and is about $45 but the one that SIM sent me based on my model number was the 65L series and was $85! I did not think there was a problem until I tried to install the gasket and found that it was really not the same (I just assumed that the filter had been "updated" to a new and improved version, but I was wrong). The correct one for my motor is clear (tan after being used) and the WRONG one was blue.

-Brent

great info thanks for posting that!

Another thing to keep in mind on the winky-blinky is that it only shows 'live' error codes from the sensors.

In other words, it doesn't store any codes from previous problems, and if a problem only occurs in a specific circumstance, the code will only show under those conditions.

Other things to add to the list, replacing the t-stats and inspecting/cleaning the PCV aka Poppit valve are also very easy tasks and can clear up some common problems. Be sure to check the spark plug cap resistance, easy to do and can lead to some weird engine behavior if they are out of spec. Also very important is to check the oil control rod clearance. If the engine never had its 10hr service, or the tech who did it was incompetent, the engine is being over-oiled, which can lead to carbon deposits accumulating on the O2 density sensor and spark plugs. Again, very easy to check and adjust yourself.

-- Tom

A couple of updates on this thread... (more learnings about the OX66).

Spot on about the oil control rod - it can REALLY make a difference in oil consumption. We did our first long trip (50+ miles) a couple months ago and actually ran out of oil while about a mile from the harbor mouth coming home. (I was dozing/zoneing out on the passenger seat and woke up to the oil alarm). Luckily we had a couple quarts stashed on the boat, which got us back home. During the ~100 mile trip, she burned through the entire remote tank (over two gallons) and the main tank (probably another 1/2 gallon). I calculated the fuel/oil ratio at something like 18:1 instead of 50:1!

She also started stumbling again (though not as badly as before) and so I did three things:

1. Replaced the (incorrect) black plastic oil rod link with the correct white one (it had been black when we bought the boat, and it looked quite different from the correct one) and installed the retaining nut that snugs against the link, which was missing ($0.40 part and $5 shipping!).

2. Adjusted the oil rod link (after disconnecting the bottom two throttles!) so that it had almost zero clearance to the stop with the throttles completely closed. The way I double checked it was to loosen the rod one revolution, then test the gap with a wire feeler gauge; it was about .020" (too much gap) so then I screwed it down one revolution (you have to go in complete revolutions for things to line up) and got it to pretty much zero clearance, then tightened up the retaining nut.

3. Removed all the spark plugs, inspected them (none were severely fouled), and then thoroughly flushed each of the cylinders with DeepCreep, and sprayed DeepCreep generously into each of the throttle bodies. Then let it sit overnight before taking it out on the water the next morning.

Wow, that DeepCreep treatment made a HUGE difference. The idle smoothed out, the RPMs came down to where they are supposed to be with the motor warm, and the throttle response and fuel economy were markedly improved. My guess is that the O2 sensor had become fouled again because of the over-oiling. A fouled O2 sensor then tells the motor to behave differently (runs rich, idles at 1,100, gimps the WOT rpms, and changes the timing to 7* BTDC, I think)

After running through about 50 gallons of gas, it looks like we used about a gallon of Yamalube, so the oil mixture seems to be correct now, too. That little oil rod can make a big difference!

From now on, I'll probably pull the plugs every 50 hours or so and douche the motor with DeepCreep and clean/re-gap the plugs just to keep things running smooth and to keep the O2 sensor telling the "real story" to the EFI computer.

Incidentally, I ran across some interesting data the other day - spectrographic analysis of a bunch of different 2-stroke oils - they all turned out to be pretty much the same EXCEPT Yamalube 2M, which had a significant amount of molybdenum (which I believe is typically a high pressure/high heat lubricant). The immediate thought was... "Hmm, interesting - Yamaha tells us we have to use their oil, which has this non-burning additive (which must produce ash/carbon), and THEN tells us we have to use their Ring Free to clean it out afterwards!

After I burn through the remaining 6 gallons of Yamalube I have, I'm going to be looking for a source for Pennzoil XLF or Premium Plus!

Thanks for all the info! My new to me boat has. 2000 ox66 225 and all this info will help greatly as i dont know much about this motor. If you eer get a chqnce a few pictures o these parts would be great! Thanks again for the info!

Hey Mike,

I've started to become somewhat of an "expert" on this motor (much more so than I ever intended) so feel free to PM me any time and I'll shoot you my phone number or email and we can chat. I'll see if I can dig up some pix in the mean time.

Some pictures.

Port side, oiling system. First picture is the CORRECT hole for the oil rod to be installed. It was originally installed in the WRONG hole by the previous owner/mechanic:





Here's an overview of the oil control rod. Notice the BLACK link end on the right side of the rod and the absence of a retaining nut behind the link end. THIS IS WRONG!! The link end should be WHITE and is actually shorter than this one:



Close up of this same thing (missing retaining nut and the WRONG link end):


And here is a picture of a shark I caught on my kayak


Wait a minute! How did THAT get in there!

Here's the housing for the O2 sensor (starboard side of the motor)



Here's an overview of the Fuel/Oil side of the motor, with some important parts pointed out: (Ignore the missing color from the top of the motor - I got a little sloppy with a painting tool)



Here's a shot of the "oh ****, I'm out of oil" switch that will pump the small amount of reserve oil up into the main tank (about 1/2 a tank's worth, IIRC):

SBH2OMan":65l138m8 said:

After I burn through the remaining 6 gallons of Yamalube I have, I'm going to be looking for a source for Pennzoil XLF or Premium Plus!

Click to expand...

Here you go... http://www.oil-store.com/
I use the 100% synthetic in my OX66.

Thanks! I've heard good things about the Premium Plus synth blend as well, and its quite a bit less $ (which is starting to get really important - regular unleaded just topped $4 a gallon here at STREET gas stations known for low prices (e.g. Fuel Depot, Arco).