Synthetic oil to help cure blue smoke?

[ewandeane]

Hello,
My 2000 Mainship Pilot 34 has started emitting more blue smoke than I am comfortable with. Yamnar 6LYA-STE
Pulled the injectors, they were showing rust. Not good.
Did a compression test on the cylinders. 200-250. Again not good. Added oil to cylinders, repeat compression test, 400+.
I will probably need the rings to be done, a job I will look into end of summer. I haven't got a cost estimate yet (any thoughts??)
I had the injectors rebuilt, (Fred Holmes in Richmond BC, awesome job) and I am going to reinstall.
In the meantime to lessen the smoke output, has anyone had any success using synthetic oil for that issue?
Other than my future ring rebuild, any other thoughts would be greatly appreciated.
Thanks
Ewan.

 

[DavidM]

I doubt if synthetic oil will do anything for the blue smoke. Synthetics usually have better lubricity than dino oil and are much more resistant to oxidation over time, neither of which will help with blue smoke.

I am a little surprised that any recreational marine engine will wear enough to produce blue smoke and have half the normal compression. That engine has been shown to go 15,000+ hours if care for well.

You said there was rust on the injectors. I wouldn't normally expect that. Is there any rust on the valve stems and springs? You can see them by looking inside the oil fill port. I am thinking you may have gotten a big slug of salt water in the crankcase which ruined the rings.

You can try running the engine hard- 2,900 rpm vs a top of 3,300 rpm for several hours to burn off carbon and reseat the rings. How do you normally run it? What is the wot rpm?

David

 

[Lepke]

Cylinders wear more at the bottom than at the top, so there is a taper. The oil ring, bottom ring, isn't doing a good job of scraping excess oil from the cylinder walls so the engine burns oil. It will burn synthetic oil just as well. Replacing the rings will help half of the problem but isn't a long term fix. It's why bigger engines have easily replaceable sleeves. The secret to longer life of cylinder walls is clean oil. If you rebore, think about adding a bypass oil filter.

 

[ewandeane]

Thanks for the reply. We’ll check the valve stems tomorrow when reinstalling the injectors. The WoT on this engine is 3300 rpm. I plan to run it full throttle when install complete. I think you are correct with water getting into the engine at some point. After talking to PO he said he always ran the engine at 2000-2200 rpm, which is one reason the injectors were in such bad shape. I suspect other parts have carbon build up as well.

 

[DavidM]

The Yanmar 6LY has cylinder liners, so definitely replace those when doing a ring job.

Running at 3,300 rpm? I hope you don't mean to do that all of the time. Ok for ten minutes once in a while to see if you are propped right and not overheating, but 2,900 rpm is the max I would run it continuously and then only if it hit 3,300+ rpm at wot.

David

 

[Rufus]

I read a credible engineering study that explained that the longer molecules in synthetics result in a better "cling factor" (my term) on cylinder walls, thereby tending to fill in irregularities better. The net effect is improved sealing of the compression rings and thereby less blowby. The tech article was somewhere on this site: https://bobistheoilguy.com/

 

[ewandeane]

Thanks, appreciate the response.

 

[BruceK]

Hope the switch to synthetic helps in the short term with the unfortunate wear. A side issue, I`m curious about the engine hours at which this issue showed itself.

 

[ewandeane]

1500 ish hours

 

[twistedtree]

With rust on the injectors and low compression on a low hours engine, it seems almost certain that it ingested sea water. Has the wet exhaust system been checked for sufficient rise and fall, and susceptibility to water back flow? I know some boats have inherently marginal exhaust designs, but don't know about this particular Mainship model. Maybe others know since several people have them?


Has the exhaust elbow been removed to inspect for rust in the elbow and turbo? What about oil testing? Peeking into the valve cover is a good idea too. Just keep in mind that water getting into the cylinders via the exhaust may not make it into the crankcase or past the valve stems to the valve cover area.


Are all the cylinders similarly low compression, or just some of them?

 

[DavidM]

Sea water ingestion is my prime culprit here. It is easy to check for water backing up into the exhaust: Remove the exhaust elbow and look inside the turbo throat. Any roughness or corrosion products is a sure sign. Also do an oil analysis which will show high Na if sea water contaminated.

Mainship 34s have poor exhaust geometry to avoid sea water ingestion. Mine had 8" of rise above sea level before I fixed it. Tony Athens recommends 12".

The fix won't be cheap: pistons, rings, cylinder liners. Plus a thorough examination of all moving parts for sea water corrosion and full after cooler servicing. A leaking after cooler is probably the second most likely culprit followed by a main heat exchanger leak.

Maybe look for a good RTO and combine the best of both engine's parts.

David

 

[sunchaser]

David
I was awaiting your take on this as sea water ingestion, with your Mainship experience, was my first thought. TT is spot on as well as any rust in the engine indicates water ingestion from somewhere.

Then the potential for a long layup as the vessel only ran about 80 hours per year. A new or rebuilt engine in this case may not solve the likely ingestion issue. Thus cause and effect remedies need examination.

 

[Gdavid]

I have had success with low compression gas engines with carbon coated rings by doing a top end soak with sea foam. I don't know if your cylinder walls are scored or the rings are rusty and stuck in the ringlands but it is worth exploring prior to the job you are talking about. The injectors will have to come back out but that is about the extent of the effort.

 

[twistedtree]

Regardless of how the engine gets fixed, if the exhaust geometry is inadequate, that's just as import to fix or it's just a matter of time before you trash the engine again.

 

[DavidM]

Regardless of how the engine gets fixed, if the exhaust geometry is inadequate, that's just as import to fix or it's just a matter of time before you trash the engine again.

The exhaust geometry of the Pilot 34 is definitely inadequate- 8" vs 12" recommended. But I have been following Pilot 34s closely for the last ten years and have seen only a few affected by sea water intrusion. Now there may be lots of others who have the problem and don't know it- yet.

I decided to fix mine and got 16" of clearance so I can sleep well.

David

 

[Kbsmd1]

Ewan,

On a previous boat with an older engine, I used a product called "Diesel Kleen" from Powerservice. The engine was good, but older and had some of the blue smoke you mentioned. I didn't think it would do much, but surprisingly, it works well. I now use it more as a preventive as it was recommended by two well respected diesel mechanics. It's fairly inexpensive and probably worth a try.

 

[FOADIAC]

I was thinking mixing elbow as well...I believe they are recommended for replacement @ 3-5 yrs or 1000 hrs...more or less...

 

[NCheaven]

Burning oil

I had considerable smoke at starting in the first 3 years (2017-2020) that I had the Camano (Volvo TAMD41P-A, 2005, now 1700 hours). I switched to Rotella full synthetic 15-40 (manual recommended viscosity), and the smoke at starting was cut at least 75% - I don't even notice smoke now. That's a somewhat different issue - Starting for me, apparently ongoing for you. Read the on line product descriptions on Rotella's heavy duty diesel oils to see how they compare performance from their dino to blended to full synthetic. Huge performance difference against their own dino and dino blend products on so many performance metrics. It's a matter of good/better/best, and $30 a year extra for 3 gallons for "best" sure makes sense to me, especially after looking at the performance specs - corrosion, engine cleanliness, shear temp, engine wear., sludge. Great information sources.

Saw someone asking $33,000 on line for a rebuilt version of my engine. You bet I'll continue using synthetic!

 

[NCheaven]

Just checked the Rotella site, and the T-6 full synthetic "additional information" tech specs page noted an improvement over Rotella's own T-4 dino oil in oil consumption. That may be closer to your concern. Good luck finding at least a partial solution.

 

[Rid]

I had a Grumman mini van with a Volkswagen diesel. It was getting hard starting, glo plugs were fine so I suspected low compression.
I was driving down the highway and it started running very rough with lots of black smoke.
Took my foot off the throttle and it had no effect.
I got it stopped and off the highway but it continued shaking blowing black smoke.
It continued running at high rpm until the crankcase was void of oil.
Really shook me up.
Can't imagine what that would have been like on the water. Never mind a Marina.
You can't turn off a diesel running off crankcase oil

 

[KnotYet]

I had a Grumman mini van with a Volkswagen diesel. It was getting hard starting, glo plugs were fine so I suspected low compression.
I was driving down the highway and it started running very rough with lots of black smoke.
Took my foot off the throttle and it had no effect.
I got it stopped and off the highway but it continued shaking blowing black smoke.
It continued running at high rpm until the crankcase was void of oil.
Really shook me up.
Can't imagine what that would have been like on the water. Never mind a Marina.
You can't turn off a diesel running off crankcase oil

The VW's after about 1995 have a valve in the air intake that will close when
the ignition key is turned off. This can stop a 'runaway' as it is called.
Failing that, stalling in gear works, just not if it is an automatic transmission.

 

[TowLou]

I had a Grumman mini van with a Volkswagen diesel. It was getting hard starting, glo plugs were fine so I suspected low compression.
I was driving down the highway and it started running very rough with lots of black smoke.
Took my foot off the throttle and it had no effect.
I got it stopped and off the highway but it continued shaking blowing black smoke.
It continued running at high rpm until the crankcase was void of oil.
Really shook me up.
Can't imagine what that would have been like on the water. Never mind a Marina.
You can't turn off a diesel running off crankcase oil

When on the water and or anywhere with a runaway diesel get to the air intake and plug it up. Without air it can not create explosion.

May see a actual air intake shutoff on many 2 stroke diesels.

 

[Rid]

It was one born out of the 70's oil embargo.
Like the next post, you need to keep a clear head on the water.
On land I had the privilege to distance myself

 

[Portage_Bay]

If you experience a run away diesel on a boat leave it in gear while you pull the air cleaner and block the intake. As tempting as it is to put the transmission in neutral the engine may then overspeed and all sorts of ugly things could happen.

 

[ronobrien]

The Yanmar 6LY has cylinder liners, so definitely replace those when doing a ring job.

Running at 3,300 rpm? I hope you don't mean to do that all of the time. Ok for ten minutes once in a while to see if you are propped right and not overheating, but 2,900 rpm is the max I would run it continuously and then only if it hit 3,300+ rpm at wot.

David

A diesel shouldn't be hurt by running at full rated RPM, as long as it's under a load. Diesels love to work. It is a good idea to run at full load (this does not mean WOT with no load) for 10 minutes or so each time out. This raises cylinder pressures which sets the rings to the cylinder walls and helps prevent cylinder wall glazing, which would result in lower cylinder pressures and un-burned fuel or excessive oil consumption. I worked for Mack Trucks for many years and it was common for guys that bought their first new diesel after having gas trucks to come in with oil pouring out of the exhaust manifolds. They all said they were taking it easy to break them in. We told them that to break it in, you load it to the max and run it pedal to the metal. The oil problem always went away.