Question for diesel engine experts

Coalman said:

Anyone have a good fuel burn rate at cruise speed (say 8-9 knots) Cummins 6bta 5.9L M3 335 hp. I’m looking at economy. Not sure if this is the engine. Any help is appreciated

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Our two 6BTA 5.9 M3 370's burn 12 liters per hour combined at 1200 RPM. That gives us 7 knots on a 48 foot boat.

Are you sure about the flow of oil through the filter? The usual flow is from the outside of the element (most surface area) to the inside and then return to the sump.

catalinajack said:

. I do not agree that oil analysis is not "us". It is not "us" only because boaters somehow think their diesel engines are different than those in fishing boats, over-the-road trucks, etc.

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I tried to say 24/7 heavy duty commercial use is not us. Certainly, analyze your oil whenever desired.

Yep it's a good idea to get oil analysis with each oil change - not very expensive. And if/when you sell your boat that long record of (hopefully) clean 'no action required' reports will pay you far more in higher sales price than the reports cost you. Not to mention it will also give you peace of mind, or an early heads up with any engine problems.

Tom A said:

Are you sure about the flow of oil through the filter? The usual flow is from the outside of the element (most surface area) to the inside and then return to the sump.

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On the OEM filters yes. On the Puradyn, no. It only passes around 6 gallons of oil per hour, entering the filter through a fairly small orifice at the center of the canister where a rubber seal is engaged when you screw the lid of the canister down on the filter.

The drawing in the link is for a different canister design than mine, which drains from the bottom, but the oil flow is the same.

https://www.puradyn.com/bypass-filter-system-overview/

FoxtrotCharlie said:

Yep it's a good idea to get oil analysis with each oil change - not very expensive. And if/when you sell your boat that long record of (hopefully) clean 'no action required' reports will pay you far more in higher sales price than the reports cost you. Not to mention it will also give you peace of mind, or an early heads up with any engine problems.

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FXTC

IMHO, oil analysis on our recreational marine engines is primarily to pick up the traces of coolant or salt water that indicate a non internal issue. These could be exhaust problems with water ingestion or an overheat warping or cracking an engine part.

On any vessel for sale, a prudent buyer should have a set of oil analysis done. If all OK with those reports, good sea trial results and maintenance records check out then some other things come into play. Such as visuals.

A crappy looking ER with rusty engines, shoddy upkeep, lots of water or residue in the bilge is run don't hide for me. Just did this a few months ago - ran. I didn't care that the oil analysis was OK.

sunchaser said:

FXTC

IMHO, oil analysis on our recreational marine engines is primarily to pick up the traces of coolant or salt water that indicate a non internal issue. These could be exhaust problems with water ingestion or an overheat warping or cracking an engine part.

On any vessel for sale, a prudent buyer should have a set of oil analysis done. If all OK with those reports, good sea trial results and maintenance records check out then some other things come into play. Such as visuals.

A crappy looking ER with rusty engines, shoddy upkeep, lots of water or residue in the bilge is run don't hide for me. Just did this a few months ago - ran. I didn't care that the oil analysis was OK.

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I don't disagree at all - just did that with our purchase. And I assume that an owner with "A crappy looking ER with rusty engines, shoddy upkeep, lots of water or residue" would not be getting regular oil analysis reports

catalinajack said:

Remove acids? Again, another misunderstanding of oil attributes. With much respect, do some self-education around TBN (Total Base Number). The TBN is an indicator of the oil's ability to NEUTRALIZE residual acids. As long as the TBN is sufficiently high, the oil is NOT acidic. Oil anysis will show the TBN and the analyzing house will tell you if you need to change the oil. As I opined earlier, many, if not most, boaters throw away good oil. The idea that oil must be changed before winter layup to avoid internals from sitting in acidic oil is preposterous regardless of what any "experienced" mechanics postulates.

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I think most of us understood what Mr. S. was referring to when he mentioned removing acids. Better phrasing would be correcting the pH of the oil, which can drop over time, and is corrected by the additive package.

Personally, I don't find it either too expensive or too much trouble to follow the engine manufacturer's recommendations regarding oil change intervals.

The acid in the oil concern was a big deal when fuel had a lot of sulfur. Much less of a concern now with ULSD. Also, for acid to attack bearings, there needs to be moisture in the oil, which can be a problem with engines with sea water cooled oil. If your oil is coolant cooled and you run at a reasonable power setting, the oil in regions gets hot enough to drive out any combustion derived moisture.

Another reason to power up for a half hour if you mostly run your engine at put-put speed. Especially last run before a period of non-use.

Ski in NC said:

The acid in the oil concern was a big deal when fuel had a lot of sulfur. Much less of a concern now with ULSD. Also, for acid to attack bearings, there needs to be moisture in the oil, which can be a problem with engines with sea water cooled oil. If your oil is coolant cooled and you run at a reasonable power setting, the oil in regions gets hot enough to drive out any combustion derived moisture.

Another reason to power up for a half hour if you mostly run your engine at put-put speed. Especially last run before a period of non-use.

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I think this is where an EGT gauge is helpful. I usually run our engine up to around 775 degrees towards the end of a day's running at "put-put" speeds. That may also be why I rarely see any soot from the dry stack.

My Puradyne filter remains full after engine shutdown by design. Once the engine dipstick shows the oil sump is full, the operating level change is miniscule.

Delpin,


sis web shows the 3306(84z prefix) as a 29qt oil capacity. the extra 3qts is not going to cause an issue because the "do not overfill" warning is is intended for when the engine is running. once you start the engine the filter will fill up almost immediately and be at the normal running level in less than 30 seconds. personally i would just remark the stick for the new static level.

captaindah said:

My Puradyne filter remains full after engine shutdown by design. Once the engine dipstick shows the oil sump is full, the operating level change is miniscule.

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There are two designs. You have one, I have the other.

BIG CAT said:

Delpin,


sis web shows the 3306(84z prefix) as a 29qt oil capacity. the extra 3qts is not going to cause an issue because the "do not overfill" warning is is intended for when the engine is running. once you start the engine the filter will fill up almost immediately and be at the normal running level in less than 30 seconds. personally i would just remark the stick for the new static level.

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The do not overfill markings are on both the"engine stopped" and the "engine running at idle" sides of the dipstick. The Puradyn filter actually takes quite awhile to fill once drained, in my size, around 10 minutes. That was really the reason why I asked the question in the first place. For those 10 minutes, is the extra oil needed to fill the Puradyn a problem, and the experts seem to think not.

Delfin said:

The do not overfill markings are on both the"engine stopped" and the "engine running at idle" sides of the dipstick. The Puradyn filter actually takes quite awhile to fill once drained, in my size, around 10 minutes. That was really the reason why I asked the question in the first place. For those 10 minutes, is the extra oil needed to fill the Puradyn a problem, and the experts seem to think not.

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even at 10 Min's its unlikely to cause a problem because you will be idling long enough to fill the filter before increasing engine speed. if this were a emergency gen that goes to 1800rpm immediately. i would put a solenoid valve that closes when the engine is not running.

Another option not discussed is to lower the filter to the same elevation as the engine sump. May or may not be possible or convenient, but certainly is simple.

Disclosure: I'm not a diesel engine expert.

Northern Spy said:

Another option not discussed is to lower the filter to the same elevation as the engine sump. May or may not be possible or convenient, but certainly is simple.

Disclosure: I'm not a diesel engine expert.

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Perhaps not, but you're the only one with the visual acuity to see the cleat resting on the hull of the unfortunate Cutwater.

In this case, moving the filter wouldn't work. The CAT sits in a bit of a well, and I couldn't get the canister low enough.

My real old 1970 bypass filters, oil goes into the bottom, the outflow is high up on the side. So about a qt of oil is always sitting in the housing. Unscrew the top , pull out the old cartridge. Only a few times have i sucked the oil from the bypass.

Factoid is this, if they are flowing oil, they will warm up. On my engines I hardly ever change the bypass filters, it is a waste of time. I just change the main full flow filters.

If they don't warm up properly, then I change them. It s just a bypass filter, not like the main full flow filter. I bet lots of people are changing them out unnecessarily.

And as they clog or restrict, they filter even finer the oil.

I have probably changed them 3 times since 1998 when I got the boat.

Delfin. What is the drain hose size? Murphy makes a oil makeup float valve. The oil supply psi should be enough to push oil through but still seal it off when not running.

BIG CAT said:

Delfin. What is the drain hose size? Murphy makes a oil makeup float valve. The oil supply psi should be enough to push oil through but still seal it off when not running.

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It's 3/4", but I think the manual shut off valve is best, since it allows me to drain the cannister when the engine is off during oil change time.

sdowney717 said:

My real old 1970 bypass filters, oil goes into the bottom, the outflow is high up on the side. So about a qt of oil is always sitting in the housing. Unscrew the top , pull out the old cartridge. Only a few times have i sucked the oil from the bypass.

Factoid is this, if they are flowing oil, they will warm up. On my engines I hardly ever change the bypass filters, it is a waste of time. I just change the main full flow filters.

If they don't warm up properly, then I change them. It s just a bypass filter, not like the main full flow filter. I bet lots of people are changing them out unnecessarily.

And as they clog or restrict, they filter even finer the oil.

I have probably changed them 3 times since 1998 when I got the boat.

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That's an interesting observation. Bypass filters work by slowly and very finely filtering oil over and above what the OEM filter does. So not changing it isn't going to have much effect other than increase its filtering capability, or so I would guess would happen as it loads up with very fine carbon. Not sure I would use the "doesn't get hot" metric for deciding when to change it, but I'm sure you're right that you could avoid changing it for a long time with zero ill effects.

Delfin said:

That's an interesting observation. Bypass filters work by slowly and very finely filtering oil over and above what the OEM filter does. So not changing it isn't going to have much effect other than increase its filtering capability, or so I would guess would happen as it loads up with very fine carbon. Not sure I would use the "doesn't get hot" metric for deciding when to change it, but I'm sure you're right that you could avoid changing it for a long time with zero ill effects.

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Ahh, someone has a brain!

"I'm sure you're right that you could avoid changing it for a long time with zero ill effects."


That would depend on how much damage you think the fines do to an operating engine.

FF said:

"I'm sure you're right that you could avoid changing it for a long time with zero ill effects."


That would depend on how much damage you think the fines do to an operating engine.

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Well, don't change filters when the engine is operating.

Depth filters work great until they breakthrough due to high DP. Then, they don’t really work much at all. This is due to the increased velocity through the media, which may make it core through or the channel through the path of least resistance.

But, in this case, since it is kidney loop filtration, the consequences of failure are minimal as primary filter is still functioning. You just loose all the good attributes it was providing above and beyond the spin on filter.

Condition based maintenance, changing the element when it hits the manufacturer’s recommendation differential pressure, is the way to maintain a depth filter. And yes, this can be a very long duration, as the engine is not in a continuous use application.

sdowney717 said:

Ahh, someone has a brain!

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I borrowed it.

Northern Spy said:

Depth filters work great until they breakthrough due to high DP. Then, they don’t really work much at all. This is due to the increased velocity through the media, which may make it core through or the channel through the path of least resistance.

But, in this case, since it is kidney loop filtration, the consequences of failure are minimal as primary filter is still functioning. You just loose all the good attributes it was providing above and beyond the spin on filter.

Condition based maintenance, changing the element when it hits the manufacturer’s recommendation differential pressure, is the way to maintain a depth filter. And yes, this can be a very long duration, as the engine is not in a continuous use application.

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Spy, wouldn't it work like a fuel filter? I thought that as the media clogged with particulates, the average size of the particle filtered went down until flow was reduced sufficiently to interfere with operation. Mind you, I'm the guy who changes both oil and all filters on the mfg recommendations, with synthetic no less. But I think I understand the argument and other than a breakdown in the media I'm not sure how a bypass filter not being changed for a long time would be an issue. A diminishing additive package would be a separate issue. In fact, my impression is that Puradyn recommends annual changes in their filter so that the additive package in the filter is replenished. Since I change my oil more frequently, I just buy the filters without the additive package.

Delfin said:

Spy, wouldn't it work like a fuel filter? I thought that as the media clogged with particulates, the average size of the particle filtered went down until flow was reduced sufficiently to interfere with operation. Mind you, I'm the guy who changes both oil and all filters on the mfg recommendations, with synthetic no less. But I think I understand the argument and other than a breakdown in the media I'm not sure how a bypass filter not being changed for a long time would be an issue. A diminishing additive package would be a separate issue. In fact, my impression is that Puradyn recommends annual changes in their filter so that the additive package in the filter is replenished. Since I change my oil more frequently, I just buy the filters without the additive package.

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Most fuel filters use mechanical surface filtration. And it is true of surface filtration, that the particles are trapped on the surface of the filter, causing the efficiency to increase as it ages. In some industrial filters (not fuel or oil, though) you actually precoat the filter with a known particulate to make it work.

Depth filters use a torturous path to trap the particles inside of the media. They generally have a distributor on the inlet to try and achieve an equal pressure load on the media.

It's been a while since my last Noria course, and more lately I've been focused on water filtration, which adds in electrical charge (zeta potential) as well as mechanical filtration, so once again, I am not an expert.

If you use the terms "surface" and "depth" in a Google search, you can get the gist of the types and difference of mechanical filtration. Just beware of sales pitches.

I liked the Noria courses as they were not affiliated with a lubricant or filter manufacturer.

I generally stay out of filter discussions because of the amazing amount of confirmation and belief bias and opinion, with no empirical data.

Generally speaking, change oil and filters based on measurable condition criteria.

Failing that, change it periodically, and often.

If it's too hard, make it easier.

If it's too expensive, find a new hobby, or anticipate failure.

I am pleased to hear that a fine vessel like yours has a bypass filter. It is the right thing to have for long term reliability.

Northern Spy said:

Most fuel filters use mechanical surface filtration. And it is true of surface filtration, that the particles are trapped on the surface of the filter, causing the efficiency to increase as it ages. In some industrial filters (not fuel or oil, though) you actually precoat the filter with a known particulate to make it work.

Depth filters use a torturous path to trap the particles inside of the media. They generally have a distributor on the inlet to try and achieve an equal pressure load on the media.

It's been a while since my last Noria course, and more lately I've been focused on water filtration, which adds in electrical charge (zeta potential) as well as mechanical filtration, so once again, I am not an expert.

If you use the terms "surface" and "depth" in a Google search, you can get the gist of the types and difference of mechanical filtration. Just beware of sales pitches.

I liked the Noria courses as they were not affiliated with a lubricant or filter manufacturer.

I generally stay out of filter discussions because of the amazing amount of confirmation and belief bias and opinion, with no empirical data.

Generally speaking, change oil and filters based on measurable condition criteria.

Failing that, change it periodically, and often.

If it's too hard, make it easier.

If it's too expensive, find a new hobby, or anticipate failure.

I am pleased to hear that a fine vessel like yours has a bypass filter. It is the right thing to have for long term reliability.

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Not sure whether the Puradyn filter is a depth, or surface filter. The oil enters the bottom of the filter, which is composed of some kind of treated polymer string. The filter material is inside a disposable aluminum cannister, which is in turn inserted into the filter body. The only place for the oil to exit is out holes in the top of the filter, so it is forced through the media, which is about 10" tall and 8" wide. The oil then dribbles down the sides of the filter and gravity drains back to the sump. So, I guess it must be a depth filter, but I don't see how the tunneling you referred to could occur. Doesn't matter for me, as I change it with the oil for drill, but am curious.

I just spent a bit of time on the Puradyne website. Not a lot of technical info there, but that is often the case.

It is definitely a depth filter.

It is recommended to change the filter, as you do, periodically as you change engine oil. I couldn't find any specifications or charts.

The filter element lives an easy short life.

No different from any other filter company, the profit is in the replacement element.

In industry, where filtration is critical, and can be tied to production losses, a bit more oversight is taken. Lube mechanics and on-site tribology labs are normal. Particularly when you are consuming tens or hundreds of thousands of dollars annually on element costs. So we wring as much out of a filter as possible to save money. Daily DP measurements are made if they aren't on-line and alarmed.

We would cut filters open and you could see how the fluid would find or make a widen section in the media. It doesn't have to be much as all it has to do is channel the flow which allows a decrease in pressure and increase in velocity. Sometimes they would be bulged and the relief path would be around the circumference of the filter.

In your case, as long as it provides good service (which I am pretty confident it does), and it isn't excessively costly, why mess with a good thing? Keep doing what you are doing.

There is a very good chance that you could go multitudes of oil changes before doing a filter change.

But you can't control what you don't measure. So with out oil analysis, or pressure differential and manufacture's recommendations, you're kind of guessing.

Next oil change, I'd cut one open with a sawzall and take a look at it.

Then I'd skip an oil change and do it again.

If possible I would consider a dp gauge, and correlate with observations, or call the company and ask for some technical info. Keep in mind, they really don't want you to extend your element life.

My gut feel is that if you put a DP gauge on it with a new filter element, it would take a long time to see it move a noticeable amount.

Again, as this is not your primary filter, the risk of failure, is identical to not having the filter at all.