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Oil check PSA

Potomacbassin’

Potomacbassin’

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Just a reminder to everyone to check your oil several times during the season. Especially with Yamaha's that are known to "make oil" when fuel bypasses the piston rings and is introduced into your oil, impacting its ability to lubricate the engine.

About a month ago I gave the dipstick a check and the level was about an inch over the high marker. Oil was last changed in the spring by the dealer and only had about 50 hours of running time since then. I do run WOT a lot which I've read helps keeps the rings nice and tight to the cylinder walls, so this result was a bit of a surprise.

Today I checked the level again and it was now 1.5 inches higher, so the problem is getting worse. Extracted the oil and I pulled well over 7 liters (spec is 6.3 per Yamaha) - it was jet black, smelled of fuel and very diluted. Refilled with 10W-30.

I'm sending the old oil off to Blackstone for analysis to confirm if there is fuel or not. In the meantime the engine is much happier sounding with the proper level and lubrication.

I'm not concerned yet as the engine is still probably breaking in but if this continues I may have to prop down and get the RPMs higher and see if that helps. Will update results when the lab comes back.

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That sounds awful. How could this happen? I will admit, I have never checked my dipstick following service from my marina. My boat stays in the water as I have no trailer, so I don’t pull the cowling off the engine very often. However, next season I intend to monitor engine components a bit more closely. So glad you were able to comfort your engine with some new oil and she is happy now.
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I had a similar problem with a yamaha f150. Dealer said to run it wot for 10 to 20 minutes at the end of every day. I did that and that solved the problem.
 
This smells (sorry for the pun) like a misdiagnosed problem. Similar observations about other injected engines commonly include a leaking fuel injector...usually after shutdown. High output run time can free up the injector so that it will seal residual fuel pressure, however that is a workaround. Injector cleaner may solve the problem, but it won't help a failing injector. In any event, washing the cylinder/rings with raw fuel is not a good thing. High output ops alone is not the way to approach the issue.

BTW: the problem may be bigger than you realize because crankcase temp and venting will eliminate gasoline over time...unless it is regularly replenished.
 
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Thanks PB -

I've already started the conversation with the dealer. Once I get the oil analysis back and can confirm fuel dilution, I'll send him a note and he'll fire it up to Yamaha. They will likely offer a canned response to change the oil and "keep an eye on it", and I'll have to do the dance for probably another few oil changes until it gets escalated and maybe they allow the dealer to test the injectors.

There's a process that has to play out so these are the opening acts. Spending an extra $60 on oil isn't the worst problem in my life but I hope this doesn't go on for another 500 hours.
 
AuthorizedUser said:
That sounds awful. How could this happen? I will admit, I have never checked my dipstick following service from my marina. My boat stays in the water as I have no trailer, so I don’t pull the cowling off the engine very often. However, next season I intend to monitor engine components a bit more closely. So glad you were able to comfort your engine with some new oil and she is happy now.
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It happens to a lot of Yamaha motors, plenty of articles and posts in other forums so it's just inherent to the design (you don't read as many issues with Merc or Zuke, so that logically rules out the operator).

I've read that automobile engines have a bit of blow by as well but they run at 200+ degrees which 1) higher temps = less blow by, and 2) may help flash a lot of that fuel out via the cranckcase vent.

But she is a lot happier now! Much easier to hear strange sounds with an OB as opposed to a car.
 
I'd suggest it better not go on another ~500 hours. Washing the oil film off of the cylinder, piston and rings will lead to expensive problems sooner than that (assuming only one injector is at fault). Just to be clear, what I'm referring to is not a blow by issue (yet). It's raw fuel from a fuel leak somewhere, frequently a bad injector. The problem also happens with some engines that have fuel lines going bad in the intake manifold.
 
Or is that oil in your fuel?
 
Your report on how much the oil level was increasing seems to indicate the calculated 5.5% dilution is a bit low, maybe that's why they specifically state their method for gauging that. Anyway dilution of 10w30 to thinner than 0w20 is a lot of dilution. If you continue to run the engine that way, shorten the change interval to, maybe, half that 50 hour plan.

Still think the problem (and yes what you have is a problem) is more than just an engine trait with blow by putting fuel-air mixture into the crankcase. That level of compression loss should show up in loss of power and, likely, raw oil in the crankcase pressure relief line (breather), assuming there is one.

IF you do spring for some form of professional carbon removal, be sure to have the injectors examined/cleaned professionally too. However before any of that, I'd have the engine scoped to see if there is any unusual carbon buildup AND if it might be limited to particular cylinders. Do any of the plugs show unusual carbon deposits? Good luck.
 
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Thanks PB -

Not sure what the dealer put in at the 100 mark - my guess is whatever NMMA / FCW oil they had laying around. I put 5w30 back in, synthetic blend.

We'll see what next steps are, dealer says they put in a work order to Yamaha in order to get authorized to poke around and see what is happening. I'm going to get what I can with the warranty coverage for now, and continue to keep an eye on it. If I'm still getting a lot of fuel past the 300 hour mark I may have to start taking matters into my own hands and go through the items you listed.

Thanks!
 
Oh OK, I thought a previous post indicated 10w30.

Noticed I failed to mention another reason why I think the 5.5% reading would be low. With crankcase heat and ventilation, all of the lighter constituents in fuel would be gone by the time your testing facility gets the sample (plus some of the base fuel too).

Anyway, hope you can chase the problem. Bet there's more than a few that would like to have the answer...
 
PartyBarge said:
Your report on how much the oil level was increasing seems to indicate the calculated 5.5% dilution is a bit low, maybe that's why they specifically state their method for gauging that. Anyway dilution of 10w30 to thinner than 0w20 is a lot of dilution. If you continue to run the engine that way, shorten the change interval to, maybe, half that 50 hour plan.

Still think the problem (and yes what you have is a problem) is more than just an engine trait with blow by putting fuel-air mixture into the crankcase. That level of compression loss should show up in loss of power and, likely, raw oil in the crankcase pressure relief line (breather), assuming there is one.

IF you do spring for some form of professional carbon removal, be sure to have the injectors examined/cleaned professionally too. However before any of that, I'd have the engine scoped to see if there is any unusual carbon buildup AND if it might be limited to particular cylinders. Do any of the plugs show unusual carbon deposits? Good luck.
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PartyBarge said:
Oh OK, I thought a previous post indicated 10w30.

Noticed I failed to mention another reason why I think the 5.5% reading would be low. With crankcase heat and ventilation, all of the lighter constituents in fuel would be gone by the time your testing facility gets the sample (plus some of the base fuel too).

Anyway, hope you can chase the problem. Bet there's more than a few that would like to have the answer...
Click to expand...
Yeah I was guessing on this post - you can't expect my old brain with all the years of inhaled gas fumes and ingested teflon-spiced scrambled eggs to fire on all cylinders!
 
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