Removing ox66 o2 sensor / analyzer - The Hull Truth

petep · 08-04-2009, 12:01 PM

I've read every thread possible on this I can find

Once the black cover housing is off, by removing the two bolts, and you can see the sensor....

the black rubber "cap" with the wires running thru the top....does this just pull off the top of the sensor....it looks like its held onto the top almost like a spark plug coil is held to the top of a plug....that it should just pull off....

but on the one site every one references on boats.net, it talks about gingerly rolling up the rubber, but I don't see how you can roll it up.

any help would be appreciated. thanks.

A1 Outboard · 08-04-2009, 03:32 PM

Put a small screwdriver under the rubber and pry it up. There is a special O2 sensor wrench used to loosen the sensor while it is still bolted to the block. When the sensor is loosened remove the bolts holding the sensor block to the engine block. Unsrew the block from the sensor and unhook the wires. Behind the sensor block is a small bar bell looking piece. Remove it from the engine block. Look into the hole you have just uncovered and find the small hole in the cylinder wall. This hole and the hole that goes through the bar bell piece will have to be cleaned of carbon. Be very careful to avoid damaging the piston or piston rings when cleaning the hole in the cylinder wall. Reassemble the parts with new gaskets in the order removed. If you have trouble understanding this procedure you should have a qualified tech do the repair for you.

petep · 08-04-2009, 08:31 PM

thank you...i should be ok...i've done water pumps, low pressure pumps, vst screens...the basics with no issues...i appreciate it.

pete

petep · 08-10-2009, 11:33 AM

for what it is worth, I know that yamaha has a special wrench to remove the O2 sensor / analyzer - which I do not own....I measured the O2 sensor "nut" with calipers - it came to 21.5mm or about 13.54/16ths...

I ended up taking a 21mm open end wrench (which never gets used) and opened it to 21.5mm by filing the insides (about 3 minutes by hand) to widen it a bit....and then I used my bench grinder to file down the outside of the wrench so I could fit it in the limited space provided...worked perfect so now I have a wrench for this task....

thanks for the help...