Blue smoke at higher RPMs from Universal M40

[EricFox]

On the weekend I pushed the throttle to 2000 RPMs for the first time since I bought the boat 1 year ago. I had never rev'd this high (never needed the speed, or the added noise and fuel consumption!). And until recently I didn't know that diesels need to be driven hard periodically. However when I went above 1800 RPMs I was getting a lot of blue smoke in the exhaust. When I saw that I immediately throttled back down. I repeated and got the same result. I figure my next step should be to do a compression test, but before I do that, I'm wondering if I should let it run at somewhere between 2000 and 2500 RPMs for a few minutes to see if it clears. What I don't know is whether or not I risk damaging the engine permanently if I do so and it turns out that I have worn piston rings or poorly sealing valves/stems. Any recommendations?

 

[Loren Beach]

Hi Eric,
It will help other owners to try and help you if.... you complete your site bio with a make/model of boat and engine. Next, complete your sig line to show boat model, engine type/hp, and sailing area. And, how many hours on your engine?
Remember, even the great Sherlock Holmes observed and collected lots of clues before starting to ID the guilty culprit. Explaining symptoms to strangers is kinda sorta like that!

Thank you.

 

[Christian Williams]

I'm curious what boat speed you get with 2000 rpms. I get maybe 5 knots, in flat water. I cruise at 2300 and six+ knots. . The engine is supposed to reach 2800 rpms, where I get 7 knots+. So, is the tach accurate? This is guessing you have an E38.

We don't have any threads specifically labeled blue smoke. Here's a smoke thread:

What color engine smoke is this?

Link to video here: https://photos.app.goo.gl/7z5Po6cXBYaYY6RQ7 After the long saga of my fuel injectors, we ended up just having the original ones sent off for service and reinstalled. The yard did a valve adjustment at that time as well. Now, my engine does this upon starting... it’s always...

ericsonyachts.org

 

[EricFox]

Thanks for the prompt to fill out my bio, Loren - it should be showing up now.

My boat is an E381 with a Universal M40 model 5432 engine. It has just shy of 4000 hours. Last summer was my first year with the boat - I only put ~50 hours on it, almost all in chunks of 30 minutes coming in and leaving the harbour. I haven't done anything to it apart from changing engine mounts (wrote a post a few weeks ago describing my method) - just the usual yearly oil change (semi-synthetic diesel engine oil 15W-40), change of oil and fuel filters, and change of impellor.

Christian, the tach isn't easy to see from the wheel so I don't reference it often, but my recollection is that I reach ~5 knots at 1500 RPM, and was hitting 6 knots when I had it up to 2000 RPM. Maybe my tach reads high?

Regarding the smoke, it is definitely blue and has the odour of burning oil, hence my suspicion that a compression test is in my near future unless I get brave and run it hot for a while and discover that the smoke clears ;-)

 

[Christian Williams]

Tachometer sounds ball park. Not all that important except for how high RPMS you can reach, otherwise ears work pretty well.

Even so, I sprung for $20 to check mine, as many here have:

Recommendations for laser tachs?

As the title says - anyone have recs for a remote tachometer I can use to verify my tach readings? Looking on Amazon they seem to range from $20-200 and I'm not sure what I'm looking at, to be honest.

ericsonyachts.org

 

[Glenn.225]

Hi Eric
Many years ago I was a diesel mechanic. Your blue smoke is oil burning, highly likely from glazed cylinder walls allowing oil to get past the oil control ring(the lowest ring on the piston).
Diesels are designed to work and like to run at or near full throttle for considerable amounts of their operating time. Extended running at low rpm coupled with light loads is a recipe for wear, as you are experiencing. I would suggest you take the boat out and give her a good run(say 2 or 3 hours) at full throttle into a good head wind, if you can get it. Of check oil first and closely monitor engine temperature and exhaust during this.
Way back when, we would use a couple of handfuls of scouring powder dumped into the intake on big Detroit's to help with this but I do not recommend this on small diesels.
My procedure for longevity is to start engine let idle 20 or 30 seconds to get oil circulating then go to 1000 rpm for 3 to 5 minutes (depending on how warn it is) then back to idle and into gear. Then a couple of mins at 1000/1200 RPM (this will probably get you out of the slip) then up 3/4 throttle or better for the rest of the time. Running at full throttle will not hurt your diesel engine. They do it all day every day in some industrial settings.
After use you will want the engine "rest a bit" that is to run at 1000 RPM for 5 min again then to idle and shut down.
Hope this helps.

Cheers
Glenn

 

[Christian Williams]

Good to hear from a diesel mechanic.

When you open the throttle on the 5432 you should get near 2800 RPMS, although it depends on the propeller among other things.

That's loud, but more important it will give a picture of your cooling system. So keep an eye on the temperature gauge. It should not rise above 180, or maybe 190. If it does, reduce throttle such than the temp returns to normal range.

Many of our boats overheat when run at high RPMS, which usually just means the cooling system is in need of attention. The heat exchanger needs to be cleaned ("boiled out") periodically, and old hoses can restrict flow with gunk buildup or simple old age.

Cooling system maintenance is something we can do ourselves and nothing indicates it is time like running it hard for a while.

 

[reginaldobaker]

All good information so far on this thread. Am not familiar with this specific engine but from experience with other diesels:

I would personally recommend using conventional/dino oil as opposed to the synthetic blend you mentioned (unless this is explicitly called for by the manufacturer). Do not have concrete data to back this up but have heard folks mention older engines (specifically older International Harvester) can burn synthetic more easily - plus would assume that is what was used when the engine was new. I like the Kirkland brand 15w-40 but players choice.

The service manual for the volvo penta md6b states oil levels should be observed before and after running the engine - it's possible the oil may be over/under-filled contributing to the burning.

 

[EricFox]

Wow, thank you all for the great advice - very much appreciated!

Glenn, I got similar advice from a diesel mechanic today. In particular, he recommended giving it a good run before bothering to hook up a compression tester. What led to take the RPMs up last weekend was the recent realization that I haven't been doing the engine any favours by babying it. I'll start to follow your recommended operating procedure.

Christian, to your comment about temperature, the diesel mechanic asked me how hot the engine gets and I told him that the temperature gauge only moves above the lowest level (120F) if I'm motoring for 30+ minutes. And that I have never seen it climb higher than 140F. He said that it should be hitting 160F within a few minutes of startup. He seemed to feel that part of my problem may be a "stuck" thermostat that is leading to the engine running colder than it was designed for. Indeed, I see that the manual calls for an engine operating T of 165 to 195F. It also says that the valve opening T in the thermostat is 140F and that the valve will be wide open at 165F. Some extra thermostats came with the boat (picture below). Based on the manual, the thermostat should be in the location pictured in the second and third pictures. I'm assuming that if I unbolt that housing I'll be able to pull the existing one out and replace it.





Christian, also to your comment about the tach, that may turn out to be the solution. The tach was temperamental last year. I traced the problem to a contact that had vibrated loose. I checked that today and found that it had backed off again. I reseated that and ran the engine and the throttle level to achieve a given RPM level was lower than what I was seeing on the weekend. And at 2500 RPM there was no blue smoke. I'm suspicious now that the tach has been reading inaccurately (low) and that the blue smoke was associated with significantly higher RMSs than the gauge was telling me. That would also explain why I have been seeing higher speeds than you for similar purported RPMs. I didn't have some to take the boat out today - I'll do that on the weekend and take note of what speeds I achieve with what I believe will be more accurate RPM readings.

Reginald, that's a good observation regarding dino oil versus synthetic. I used semi-synthetic because that is what the previous owner used, but I'll give regular dino oil a try when I next do an oil change.

 

[Christian Williams]

The thermostat question gets kicked around a lot. I eventually took mine out and boiled it in a pot, and observed that it began to open at about 160F and fully opened at 180F. They're inexpensive and easy to change--once you guess which one to buy.

Universal 5432 Engine Running Temperature

During the 15 years I've owned the E38, I have generally had excellent performance from the 5432 diesel engine. It drives the boat at 6+ knots (3-blade feathering prop) and runs smoothly. The engine is under the companionway and is closely confined in there (forward head and shower interior...

ericsonyachts.org

 

[EricFox]

So it turns out that the thermostat was bad, though not in the way I expected. With the engine always running cold, I expected it to be stuck open, but when I removed it it was closed, and when I put in boiling water it didn't open. I have no idea what to make of that. But with a new one installed (started to open at ~150F in a cut of hot water and fully open at 160F), the engine now warms up to run at ~150F - still a bit below what the manual calls for, but better than before. As far as the blue smoke, I think there is less, but that may be wishful thinking (wishful seeing?) - it was very windy when I tested it which led to the smoke dissipating quickly. I'll have to wait for a calm day to properly judge what it looks like now versus two weeks ago when I first noticed it. It still kicks in at 1800 RPM and gets worse as the revs climb.

Christian, here are the speeds that I'm seeing (SOG by GPS) at different RPMs on smooth water (folding prop so not the most efficient):
1500 4.9 knots
1800 5.8
2000 6.5
2300 6.8 or 6.9

For now I think I'll continue to motor at ~5 knots unless I'm in a particular hurry or need the added punch to tackle heavy seas, and won't worry too much about burning oil when operating a higher revs. I'd still like to do a compression test to satisfy my curiosity, but there are a few other items on my 'to do' list that will have a higher priority for now.

 

[Pete the Cat]

So it turns out that the thermostat was bad, though not in the way I expected. With the engine always running cold, I expected it to be stuck open, but when I removed it it was closed, and when I put in boiling water it didn't open. I have no idea what to make of that. But with a new one installed (started to open at ~150F in a cut of hot water and fully open at 160F), the engine now warms up to run at ~150F - still a bit below what the manual calls for, but better than before. As far as the blue smoke, I think there is less, but that may be wishful thinking (wishful seeing?) - it was very windy when I tested it which led to the smoke dissipating quickly. I'll have to wait for a calm day to properly judge what it looks like now versus two weeks ago when I first noticed it. It still kicks in at 1800 RPM and gets worse as the revs climb.

Christian, here are the speeds that I'm seeing (SOG by GPS) at different RPMs on smooth water (folding prop so not the most efficient):
1500 4.9 knots
1800 5.8
2000 6.5
2300 6.8 or 6.9

For now I think I'll continue to motor at ~5 knots unless I'm in a particular hurry or need the added punch to tackle heavy seas, and won't worry too much about burning oil when operating a higher revs. I'd still like to do a compression test to satisfy my curiosity, but there are a few other items on my 'to do' list that will have a higher priority for now.

I am not sure of what the WOT speed of your engine is supposed to be, but I would caution you against running it at lower speed to "save" the engine. Diesels want to be run 80% of WOT at cruise and the cylinders will glaze (and burn oil) if they are run at low temps that do not completely combust the fuel in the cylinders. (For lurkers who have read Nigel Calder's article about it being OK to run an overpowered recreational diesel at less than 80%--I have written him about this, and he has admitted that he misled folks with that advice.). Diesel engines want to be thoroughly warmed up when they are run and they want to run at a set temp (usually 160-180F) and fully lubricated during that time. Burning some oil is a lot better than glazing the innards of your piston cylinders and rings. I am convinced that most recreational diesels die not of use, but of being run too cold, for too short a distance, and at too low an RPM. But that is just my opinion, but I think the vast number of old diesel mechanics will agree. Seems like your prop is likely overpitched and that is not good. Again, this depends on the WOT of your engine but I assume it is 3000 or. 3200 RPM. The engine should be able to produce this under power at some point with a properly pitched prop. Do you have an aftermarket prop??? Ericson actually did a good job sending their boats out of the yard with decently pitched props. Maybe your Tach is off--do you have a non OEM alternator (where the signal for the tach comes from)? FWIW. As usual---More questions than answers.

 

[EricFox]

Good food for thought re: running hard despite the burning oil - lesser of 2 evils. I'm suspicious of my tach - when I return from cruising that will need to be on the to-do list. Yes, the alternator is non-oruginal, as is the folding prop.

 

[David Grimm]

I briefly scanned this thread, but felt the need to reply. I run a 160 degree stat. At approximately 1600 rpm I'm at 6 knots. Recently I ran that for approximately 22hrs from Poughkeepsie NY to New Haven CT. I do see a whisp of smoke out the tail but never burned a drop of oil. Temp always at 160. Block Island, RI. to New Haven, CT. Took 10 hrs. at 1700rpm. 7 knot cruise. 8.5 max with current. 3 blade prop is stock I assume.

I wipe the black soot off the hull when I get to port. It's normal for this engine. You could run street diesel at a premium (highway tax) $ low sulfer. Not sure how the injector pump would like this being that the sulfer is supposedly a lubricant. I used street diesel in my 20 gal of jerry cans. Didn't notice much of a difference.

Ps. I tested my rpm with an external gun that reads a sticker put on the crank shaft. I do not run wide open throttle. I run at a comfortable speed to vibration compromise.

 

[Christian Williams]

At 1600 rpms I'd be at five knots. I cruise at 6-6.5 knots between 2000-2300. At WOT, 2750 (spec is 2800), I get 6.9 - 7.1 knots under perfect conditions.

MIchigan 3-blade sailor prop. Dive service monthly, so such different reports must be related to the propeller. My panel
rpms confirmed with $20 digital photo laser tach.

Engine temp is always 180. At full cruising speed, meaning before the stern buries, there is always steam Sometimes at startup there is steam, which I think relates to the dew point.

My diesel troubleshooting book, consulted yesterday, notes a useful characteristic of smoke vs. steam -- smoke stays much lower above the water, whereas steam rises.

 

[EricFox]

I'm back from our summer cruise during which I had the opportunity to run the engine hard for stretches of many hours. There appears to be slightly less oil leaking into the cylinders at high RPMs than there was previously, but that might be more seeing what I want to see than reality. However the onset does now seem to come at 2000 RPM rather than 1800 RPM.

Christian, in flat water I hit 4.9 kn at 1500, 5.8 kn at 1800, 6.4 kn at 2000, 6.8 kn at 2300, and 7.1 kn at 2700 (WOT). That tells me that my RPM gauge probably isn't too far off.

Curiously, there seems to be a slight correlation between drive shaft vibration and the appearance of smoke, i.e. sometimes less smoke as I increase RPMs if that puts gets me to a sweet spot where vibrations are lower. It makes we wonder if misalignment between the prop shaft and engine is putting distortional stresses back into the engine as the revs (and vibration climb). I went back to have another go at aligning the engine (changed mounts back in June), but there is so much slop in the prop shaft that I couldn't determine which way I would want to move the engine to improve alignment - I can move the prop shaft where it mates to the transmission by several mm in each direction. I don't have a good comparative reference, but perhaps time for a new cutlass bearing - the rear one that is just forward of the prop looks good, but I assume that there is also one just inside the hull (and aft of the dripless seal) - that's where the slop appears to be.

 

[Christian Williams]

I am not very knowledgeable about this stuff, and our rpms do match. Like most of us, I adjust rpms so that stove doesn't rattle, or just to find the diesel vibration sweet spot. I guess your vibration is more than the expected.

I swear my drive shaft had a bend in it between cutlass and hull. You could see it when the prop was turned on the hard. It never caused a problem, and when a new shaft was installed (for other reasons) it didn't make a difference.

You have smoke--but is it necessary to add oil?

 

[ConchyDug]

There is no bearing aft of the shaft seal. It's just a hole and the stem tube for clamping a seal bellows on.

Mainesail has decent article on it but I wouldn't follow his advice on painting the coupler or PTO... they are machined for tolerance painting removes the tolerance. He was worried about corrosion but the areas that matter are the corrosion susceptible machined faces so why bother. I'd say it's bad practice for the nuts and bolts to be torqued down on painted spinning things, this can introduce other problems.

On shaft alignment you wanna check for parallel offset which is done by pulling the coupling/shaft back where it's free floating, where a straight edge can be used to gauge offset(kinda ballparking it as sailboats have some crazy wide tolerances). You just don't want the shaft hard on the side of the stem tube or having to force it to line up with the PTO. Then pull the coupler back on to the PTO flush then do your 90° checks with a feeler gauge. Once you get it lined up, have good mounts, proper valve timing, and more than 2 blades on your prop it'll feel like a sewing machine. There are a few rpm bands these small engines don't like so just throttle up or down to avoid. Attached images for visualization.


Blue smoke to some degree I think is a feature of an old small diesel. If it's excessive and you are having to service oil between oil changes then there might be a problem.

 

[EricFox]

It's good to learn that there is no bearing where the prop shaft enters the hull - it now makes sense why there is so much slop in the prop shaft. And it may be that I'm not as misaligned as I feared based on what I did relative to what you described Doug. And since the new mounts are positioned where the old ones were to within ~1 mm (including the heights), I'm probably good. The vibration seems significant to me, but I don't have many references. And my prop is a 2-blade - I hadn't considered that that might play a role.

As for the blue smoke, maybe I'm worrying unnecessarily about that also - it looks and smells bad, but the oil level isn't changing noticeably.

 

[ConchyDug]

If you do the coupler feeler gauge check down to a gnats abdomen and it's still rough, I'd check to see if the prop is clean. A 2 blade fixed will feel relatively rough compared to a 3 blade. If it's a 2 blade folder those can really feel rough if they are dirty and don't open right. Frequency/amplitude of the vibrations can tell you something as well, also are the vibes happening in neutral vs in gear(engine vs. drivetrain).
Yeah the oil thing kinda hinges on how much smoke, just a wisp of blue smoke at idle or like a Cheech and Chong amount of smoke? If it's thick you are getting blow by from a worn ring or valve.