1998 Ox66 225 Oil Leak behind the o2 sensor. *pic*

[Mycophiles]

I just got this motor and once I got it home I was doing all the maintenance. I ran it for the first time and heard a ticking. In doing some research I found that it was the o2 sensor which was 1 big solid ball of carbon. However; when I pulled the o2 sensor off the motor a bunch of oil came out of the o2 sensor housing and then a bunch of oil drained from the line that connects to the motor underneath the fuse block.

Things to note: Right before I ran it for the first time I used the switch to fill the oil tank on the motor to see if it was working. The container was fairly full but it filled it the rest of the way.
I noted that the starboard bank of spark plugs were oily. Also, this port did not leak when I was inspecting before I bought it. It smoked a bit more than after I did the o2 sensor. There is not a spec of rust or oil on this motor ( well.. before the leak ). This motor looked like it came off the factory room floor.

boat oil2.jpg

[Mycophiles]

I've heard something about the air silencer being removed and re-installed incorrectly causing leaks. On this engine right before I bought it the silencer was removed and re-installed. I haven't had much luck looking around and asking online and I figured it's best to have one anyway so I've ordered a service manual that should be here on Friday.

I haven't even found out from looking online about the hoses. What are these hoses for? What do they do?

[TownsendsFJR1300]

Who did the R&R?

Even so, might want to look at the parts list above, in blue (Buy Yamaha Outboard Parts) and see what's where.
Depending on how it's set up, I'd probably inspect closely or pull apart and re-install. (should it not be installed correctly)..

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[Mycophiles]

I looked around the motor and found there is a hose that goes to the oil reservoir and that's the only thing that could leak. I've confirmed that in the drawings also. This is what the breakout shows for the part that's leaking. It just calls it a nipple. I have not idea what it's for. I'll order a new hose and replace it. It's just odd that it wasn't leaking when I test ran the engine but as soon as I install it on my boat.. .run it for 20 seconds.. then pull the o2 sensor it leaks a ton. Just odd.... If I knew what it was for I might be less worried. The manual should be coming in anytime now... says today.

[99yam40]

what part is that nipple on?
and where does the other end of that hose go to?

[Mycophiles]

what part is that nipple on?
and where does the other end of that hose go to?

It goes into the block below the 02 sensor on the 2nd cylinder on the starboard side. Hose goes to intake manifold... it kind jumpers from one intake to another. You can see the other grey hoses in this pictures. This one goes to the bottom of the intake manifold.

[99yam40]

just guessing but they could be crankcase recirculation .

liquid residue of oil and gas that is not pulled into the cylinders and burned has to go somewhere.
it pools up at the bottom of each cylinder crankcase and needs to be sucked out back into the intake as the motor runs.

I know at least one check valve is in each of the lines on my C40TLRX the rest were just nipples.
. 3 out of 4 were bad when I checked them and replaced all 4

[Mycophiles]

just guessing but they could be crankcase recirculation .

liquid residue of oil and gas that is not pulled into the cylinders and burned has to go somewhere.
it pools up at the bottom of each cylinder crankcase and needs to be sucked out back into the intake as the motor runs.

I know at least one check valve is in each of the lines on my C40TLRX the rest were just nipples.
. 3 out of 4 were bad when I checked them and replaced all 4

Any reason why one would suddenly leak a ton of oil down the side of the engine? Could it be that the moving the motor from one engine to another dislodged something? I have no idea.

So I need to replace these? I have a spare engine it's a 2001 OX66 200hp .. Ill look to see if they are the same. I hear they are pressed in... twist and pull will remove them I hear. I probably should order a couple just to have them.

[99yam40]

I would talk to a tech at a rebuild shop to see if some are check valves & which ones.
then test to make sure the CVs are still good(if it has some).
if CV are bad I believe the system does not work as designed and may not suck the liquid residue out

[Mycophiles]

I would talk to a tech at a rebuild shop to see if some are check valves & which ones.
then test to make sure the CVs are still good(if it has some).
if CV are bad I believe the system does not work as designed and may not suck the liquid residue out

Ok I talked to a mechanic and he said first to check the LP fuel pumps. He rarely sees issues with the CV's so he wanted me to replace these first. I thought it's not the worst Idea as I don't know anything about the motor's maintenance history. I'll do this first. While it runs I don't see any leaking so I'm not sure how I'm going to know if it works or not.

[DennisG01]

Maybe I'm missing something and not thinking through this all the way, but... can you verify where the leak is coming from? Clean everything off real well and monitor closely. I see three possibilities... an old/brittle hose, cracked fitting/nipple or the fitment between the fitting and block.