OX66 oil pump linkage adjustment

[rangr02]

Hello all, thanks for this great site!

I have researched linkage adjustment on my 99 250 ox66 and have found two answers to the same question. Although the factory manual states adjust the link against the stop with no clearance, I have found several sources (including the SELOC manual) stating .040 clearance with the throttle valves closed. The link is currently adjusted to .040 and will need the rod shortened as I have read about to get zero clearance. Why am I worried? Well, this is a new engine to me and I am still trying to get the maintenance updated. Since I had no records from the prior owner, I have been working through the factory schedule one system at a time. She smokes on start up and always has wet (but not oily) plugs, even the new ones. So far I have replaced all three fuel pumps (one was bad), cleaned the fuel filters, checked TPS, idle and crankshaft position sensor. The famous O2 sensor has received the most attention. Although the original sensor was dirty, it was not completely blocked by carbon so I cleaned it and ran it while de carboning the head with sea foam. When I finally got the test harness from yamaha, it didnt surprise me to fail the widely publicized test from the bass boat forum. It reads .7 volts regardless of plugging the number one throttle valve hole. I have the new sensor but unfortunately the wrong gaskets were sent so its not installed yet. I'm not going to install it anyway until the oil linkage issue is resolved, no use in fouling a $220.00 sensor...

So, whats the magic number for the oil pump linkage? I am leaning towards zero clearance, any suggestions?

By the way, I havent gotten to the thermostats yet. They are next on the list. The more I read this forum about this engine, the more I realize there is a lot of work to be done. But I gotta go fishing sometime...

[slim]

the correct adjustment for this specific motor is none at all. the oil pump lever should contact the stop when fully closed. this is the procedure directly from the yamaha manual.
1.disconnect the oil pump link rod joint.
2.fully close throttle valves. this means backing idle screw off all the way also.
3.turn the oil pump lever so it contacts the stopper in the fully closed position.
4.adjust the position of the oil pump link rod joint until its hole aligns with the set pin on the oil pump lever.
5.tighten the locknut.
6.install washer and clip.
hope this helps you out.

[pete28]

how was the motor running before the maintance. did you have any problems like serging , stalling , bogging etc.

[rangr02]

Thanks, Slim and Pete.

Since posting I have found the plastic link connecting the oil pump control rod to the shaft coming out of the power head was loose. Apparently it should have been made out of metal, it is only held to the shaft by a small cross pin and has since worn to the point where it causes a lot of slop. Another link is on the way and I'll set the clearance again.

Slim, that appears to be the same procedure as my factory yamaha manual suggests. I have found another suggestion from a yamaha mech who specifies a clearance of .005 to .010 with the throttle valves closed. I'll post results when the new link arrives. Right now there is too much slop to work with.

Pete, the engine ran fine except it always idled rough which I attributed to running on 4 cylinders under 2000 rpm as it is designed to do. I've been trying to cover all scheduled maintenance since I dont know the history on this engine and I usually take it 10 miles or more offshore.

For everyone with a 250 ox66, I am working out the problem with the superseded O2 sensor gaskets. The gasket available is a newer two piece set that will not fit the original O2 holder. Apparently the correct one piece gasket and associated o-ring and seal needed for the original equipment O2 holder is no longer available. I have the newer O2 holder on order to see if it will fit my original power head. An expensive solution ($115.00 for the new O2 sensor holder) but it may be the only solution. I'll know in a few days.

Thanks again for the replies.

[rangr02]

Mystery solved.

Evidently my 1999 engine has an updated block. With no records, I had no idea of its history. I'm learning fast...

The O2 sensor holder on my engine is the updated holder found on 2003 and later engines. It requires a one piece gasket, an o-ring and a seal. The original O2 holder on a 1999 engine requires a two piece gasket only. Parts are once again on the way.

If anyone is replacing or working on an O2 sensor on a 250 OX66 and your gasket set doesnt look like the one you see in the parts diagram for your year model, take a look at the 2003 model. Yamaha updated the sensor holder and gasket kit in mid 2003.

Anyone know how to access yamaha tech bulletins? I cant find anything on any of the forums or on the web.

[pete28]

let me know if the new o2 makes it idle better . I hope it all works out for you, best of luck

[rangr02]

The O2 sensor did the trick. It took a while to get the correct gasket kit, but its all back together again.

Still havent found the plastic arm I'm looking for on the oil pump control linkage. I've got the parts guys searching now. What I thought was the correct part turned out to be the plastic link for the oil pump control rod. I need the plastic arm that the "link" attaches to. Hard to describe, but the parts guys are on it. Once the new plastic arm is in place, I'll reset the oil pump control rod clearance and be done with maintenance for a while.

Pete, the idle is just like always. I didnt see any difference from the new O2 sensor.

Time to go fishing, thanks to all for your help!

[Javena69]

I think is the plastic part for the link. Opposite from the oil pump 6R5-41237-00-00

[boscoe99]

Responding to a 15 year old post? Really?