How to run a common rail

[Hippocampus]

Was brought up to warm up a diesel before leaving, let it cool down before shutting off (good for turbos especially ) and if not run with a fair load run it near WOT to burn off carbon periodically.

Now with newer boats all being common rail I am confused.
If run at very low load for a length of time should you still run it at or near WOT shortly before shut down ?
My crude understanding is given efficiency of fuel burn no carbonization should occur so maybe this isn’t necessary.

Been told running oil through it and slowly cooling the turbo by leaving it on idle for 5-10 minutes before shut down is a good idea. There’s no such teaching for the turbocharged common rail diesel in my Jeep. Why? What’s best practice for a marine common rail?

Been told compared to NA mechanical diesels common rail is super sensitive to bad fuel. What if any precautions do you take? ?additives? On board polishing? Additional filtering beyond OEM stock? Have you followed CaptWil’s advice? Do you periodically have the yard polish your fuel for you? Do you only store with full tanks? Have you added water traps to fuel tank vents? What do you do?

Any and all thoughts appreciated but please include the reasoning behind your advice. Thanks

 

[psneeld]

Pretty much none of those things was I ever taught to do or experienced in commercial work. But know they are common thoughts around many docks.

However some of the underlying reasons are there but handled differently in my experience and learnings.

No warmup at dock, get a light load on it ASAP. Now sure, if pulling a a barge away from a pier and need to use near full throttle right away, get the oil temps up a bit first. Otherwise just no high rpm operations till warmed up a bit, but never at the dock.

Yes the turbos need to cool down, but the 3-5 minutes throttled down coming to a mooring or dock is usually plenty of cool down time. Longer if a specific engine manufacturer recommends it.

Don't know about Jeep turbos. Often automotive comparisons are made but not always accurate for the marine application and vice versa. While I think some marine engine manufacturers recommendations are a bit weird, they may be justified for their particular engines and worth serious consideration before abandoning them. Old engines like Ford Lehmans have outlived a lot of the original recommendations such as oil types.

You should never need WOT to burn off carbon, just whatever speed would bring it back to the high end of normal operating temps (as specified by the manufacturer).

Fuel precautions for any diesel are a good idea. If the source is reliable, pre filtering is done by almost nobody I know. If it's coming out of 55 gallon drums or some rust bucket marina....sure. I have seen more bad fuel than I would think come from very reputable marinas AND airports.....but it really is the rare exception. Fuel lubricate on high end diesels is probably not a bad idea...but as CAT recommends...use it if the fuel warrants it. Biocide? Definitely for fuel that doesn't get used fast in warmer climates. Fuel polishing is a personal decision...but I think by people and ships that ocean cruise...being careful of what you put onboard...put it into a separate tank that can be polished and transferred to a day or primary use tank for engine feed is the ticket.

 

[Roger Long]

The last boat this naval architect designed had common rail diesels. They could not be guaranteed without an on-board polishing system. The owner did get a waiver because they have their own 10,000 tank at their base and keep that fuel well filtered and tested.

I would install an onboard polishing system if I had common rail engines. Use big industrial filters with cheap elements and much more debris capacity than Racor's. It's not an expensive (in boat terms) system to install.

Forget about periodic tank polishing for these engines.

 

[Roger Long]

Installing separate pickup's and returns for a polishing system is generally recommended but may add considerable cost. Here is a system I designed for a friend who has had good experience with it:

Fuel feed, either from tank or selector valve for multiple tanks, goes to the big industrial filter. Shelco filters are a good source. Then to a transfer pump rated for continuous use. Filtration is more efficient if fuel is pushed through but you want the filter to protect the pump.

Fuel then goes to a day tank mounted above the level of the engine mounted fuel pumps and entering at the bottom. This tank has a larger return line near the top that goes back to the main tank or selector valve/manifold for multiple tanks. The tank has a vacuum relief valve at the top. The engines are gravity fed through the regular Racor filters from this tank. I tee'd this return line into a fuel fill hose on my sailboat. That is a violation of best practice but I had no problems over thousands of miles.

Fuel is constantly running through the day tank so it stays flushed and can not build up crud. You don't have to worry about forgetting to pump it up and it can be smaller than a day tank, maybe an hour tank.

Engine return lines can go back to the main tank or manifold or to the day tank.

A bypass so the engines can draw normally in event of polishing pump failure can be installed.

 

[rgano]

Simple. Follow the engine manufacturer recommendations. A very well qualified mechanic added when I questioned him about the warmup recommendations on my Yanmar was, "Well, you don't get out of bed in the morning running instead of walking do you?"

 

[twistedtree]

Any warm up and cool down happens as a matter of course just in getting untied, away from a dock, and out of a marina or anchorage. A moderate load while doing these tasks helps. Just don't open it up until it's at full temp. Then the reverse is true at the end of a run, whether you are docking or anchoring. You will have idled plenty before you are ready to shut down.


More filtration is required for common rail, but it's all done in the engine and external racor or equivalent. You will likely have two fuel filters on the engine, and they should be replaced at the specified interval. The engine manufacturer will also specify the micron rating for the external filter, and you should follow that. Don't listen to your mechanic, listen to the engine manufacturer. It's all set up for progressive filtration, so don't defeat it.


As for a hot run at the end of the day, I don't think it can hurt, but I also think it's much less necessary with a common rail engine. Common rail injection gets a cleaner and more complete burn by design rather than being so dependent on the internal operating temp of the engine. This is why they start easier, don't smoke like crazy while they warm up, and don't soot up as much when running at lighter loads.

 

[rslifkin]

Generally once an engine has been running for 2 minutes at high idle and is confirmed to idle well, it's time to go. For cool down, by the time you're done with the first few lines and sure you don't need the engine anymore, it'll be fine to shut down unless you used a ton of throttle while docking. Water cooled turbos don't need a long cooldown like oil only turbos do. Some cars have a coolant pump to help cool the turbo after shutdown to further reduce the cooldown need.

For a heavy load run up, it depends on the engine and how light a load it was under. Most modern diesels aren't all that sensitive to underloading, but it varies between engine designs. As long as you get enough load on it periodically to see positive turbo boost, it'll probably be fine.

 

[Codger2]

Any warm up and cool down happens as a matter of course just in getting untied, away from a dock, and out of a marina or anchorage. A moderate load while doing these tasks helps. Just don't open it up until it's at full temp. Then the reverse is true at the end of a run, whether you are docking or anchoring. You will have idled plenty before you are ready to shut down.


More filtration is required for common rail, but it's all done in the engine and external racor or equivalent. You will likely have two fuel filters on the engine, and they should be replaced at the specified interval. The engine manufacturer will also specify the micron rating for the external filter, and you should follow that. Don't listen to your mechanic, listen to the engine manufacturer. It's all set up for progressive filtration, so don't defeat it.


As for a hot run at the end of the day, I don't think it can hurt, but I also think it's much less necessary with a common rail engine. Common rail injection gets a cleaner and more complete burn by design rather than being so dependent on the internal operating temp of the engine. This is why they start easier, don't smoke like crazy while they warm up, and don't soot up as much when running at lighter loads.

Written with a lot of common dense....Don't overthink the care that is needed just because your engines are common rail!

 

[rwidman]

There is nothing quite so annoying as having the guy in the slip next to you decide to start his diesel engines and warm them up for thirty minutes before leaving the dock at 6:00 AM while you are trying to sleep!

I figure idling a couple of minutes and then leaving the slip (and marina) while still at idle speed is a good plan. Once out of the marina, I will speed up a bit and after a few more minutes I will speed up some more. I don't go to my cruising speed until the temperature gauge is in the normal range. My engine would never warm up at idle with no load, but it warms up quickly enough when idling out of the marina.

As for shut down, again, you will be idling through the marina and into the slip. I don't shut the engine down until the boat is secured to the dock (or anchored) so that's a "cool down" period.

 

[Hippocampus]

Been in areas where it’s wise to filter your fuel as it enters your boat before the tanks. Any of you follow a similar practice?

Thanks all for the above. Confirms my thinking. Anyone want to speak to full tanks. Have been told it’s hogwash but no air in the tank except that needed to expansion on warm days seems logical. Also water separation on fuel tank vents?

 

[psneeld]

As far as full tanks,, explosion hazard not an issue with diesel and it does depend on location climate as to the condensation worry.....also just how much fuel is present and shape of tank.

My experience says not really needed to worry along Atlantic seaboard...but huge tanks that rarely get fully turned over will in time collect all kinds of undesirables.... if not bottom feed ones which at some point start using and filtering the sludge. Even my bottom feed ones has sludge up to the outlet...from there up the fuel was great...but on a boat that probably hadn't seen rough weather in decades. As long as the fuel is regularly burned and as I poster...ideally from storage tanks to a dar tank, then again twice filtered to the engine...one should be OK on full or partially full tanks.

Filtering from questionable sources is always a good idea, not always possible/practicable.

 

[firehoser75]

Good advice from Scott and others. For common rail, fuel filtration (and therefore cleanliness, no water etc.) is even more important than NA. At a minimum follow the OEM requirements, and more is not a bad thing (except for the possibility of needing more frequent filter changes). Three levels of progressive filtration (instead of two) is a good way to go, ending with a recommended OEM on engine filter.
Long periods of idling at the dock for a warm up is not only not needed, but is a bad idea for many reasons. Diesels (like the ones in most of our boats) do not like idling with no load, to say nothing about your dock neighbours having to needlessly be disturbed by the exhaust and noise. As others stated, these diesels will warm up just fine by leaving the dock as soon as is reasonable after startup (probably 2-3 minutes or less), and leave the marina/anchorage with very low RPM's. Do not raise rpm much above idle until the engine temps are up above 150 degrees and me being cautious, I would wait for full temp before going all the way to 80% throttle (a normal high cruise rpm).

I was taught by what I consider a good source (Tony Athens) that especially for NA diesels run at low load (like my "Tug" run mostly at half throttle) that taking the engine up to 80% throttle for 5-10 minutes near the end of a longer run, and even to WOT for a minute is a good idea to exercise the turbo, burn off possible carbon buildup, and to check out the engine for signs of possible developing issues. I discovered the beginning of a very small coolant leak in this manner (it only leaked at WOT) and later changed the gasket as a result. If you run at 80% rpm for your cruise speed, then the occasional WOT to ensure all is well (short periods are all that is needed) is probably not a bad idea. I do not actually know if this "burning off the carbon" type of thing is actually "needed" for common rail, but I know that doing so will not hurt it.
Even after a WOT portion 5 minutes before going into the marina, your engine (and turbo) should get all of the cool down it needs running into the marina at very low rpm's and the normal docking (with line tying etc.) process, so shutting down once the boat is secure is warranted. Idling at the dock is again not needed and is annoying to everyone else nearby.
If your boat has large tanks with large amounts of fuel that sit for a period of time, an onboard fuel polishing system is probably a good idea. I did not use one, nor feel the need for one, as my engine returned large amounts of fuel to the tanks basically completely circulating all of my fuel on many of my longer days of operation. So on my NT, just running the boat often passed most of my fuel through the filtration.

As far as fuel additives goes, I used a biocide (makes perfect sense to me), and also added "Star Tron" diesel additive. Several years ago Practical Sailor did some testing and recommended Star Tron additive, providing good rationale. However, memory fades and I can no longer remember exactly why they thought it was good.

 

[Hippocampus]

Have watched fuel polishing done multiple ways. All fuel removed and tank in effect pressure washed via examination port. Fuel polished off the boat and returned after tank cleaned. Fuel removed then circulated through dockside device and returned. Also been told fuel polishing other than intrinsic to the boat itself isn’t worth the time and effort. Periodic polishing doesn’t remove sludge nor sterilize the tank so any potential benefit beyond water removal disappears quickly unless a wand can be introduced and using the fuel the sludge agitated. Any opinions one way or the other?

 

[BandB]

Simple. Follow the engine manufacturer recommendations. A very well qualified mechanic added when I questioned him about the warmup recommendations on my Yanmar was, "Well, you don't get out of bed in the morning running instead of walking do you?"

That's it. Now, as to what we do in practice, the following, but understand we have engines installations targeting planing. As others have mentioned, you have slow at the start and end of the runs naturally. We cruise most often at 70-80% load, depending on the boat. However, we just completed a 38 hour run where we averaged 15% load, only averaging 20 knots. We did still periodically open up to 70-80% briefly. We had a nice cool down period as we approached the marina.

I believe that varying the speed is important and continue to do so. Now on a continuous run commercial engine I wouldn't feel the need.

 

[BandB]

Been in areas where it’s wise to filter your fuel as it enters your boat before the tanks. Any of you follow a similar practice?

Thanks all for the above. Confirms my thinking. Anyone want to speak to full tanks. Have been told it’s hogwash but no air in the tank except that needed to expansion on warm days seems logical. Also water separation on fuel tank vents?

Actually I think it's wise to check the fuel before it enters the tanks. There are many test kits, some for water only and some for other things.

 

[BandB]

Have watched fuel polishing done multiple ways. All fuel removed and tank in effect pressure washed via examination port. Fuel polished off the boat and returned after tank cleaned. Fuel removed then circulated through dockside device and returned. Also been told fuel polishing other than intrinsic to the boat itself isn’t worth the time and effort. Periodic polishing doesn’t remove sludge nor sterilize the tank so any potential benefit beyond water removal disappears quickly unless a wand can be introduced and using the fuel the sludge agitated. Any opinions one way or the other?

External polishing is normally done simply when a major issue exists and there's a large quantity of unusable fuel. In those circumstances it's of great benefit. Routinely wouldn't be. Also if major issues, then cleaning of the tank may also be called for.

 

[Hippocampus]

That’s my understanding as well. Was asking about comparing techniques.

 

[High Wire]

The manual will say if there are any special requirements. For example Yanmar has a statement to”race” the engine several times before shutting down. What the heck was the intention there? My guess is that something got lost in translation! After the manual, asking a manufacturer specific tech for recommendations would be better than generic guidance.

 

[dhays]

Since I am new to larger Diesel engines, I have asked similar questions.

My boat has a turbo-charged Cummins 5.9L QSB engine rated at 380hp. Unfortunately, I have the opportunity to spend some time with a very experienced and senior Cummins mechanic. I asked him some of those very questions. This is what he said.

1. Start up and make sure the idle is smooth. Then leave the dock. Allow the temps to rise to close to normal operating temps before adding a lot of power.

2. Don’t bother with short periods of high power. He said it was good advice for order engines, but not necessary for modern electronic common rail engines.

3. Give the engine a short period of low speed running before shut down to allow the Turbo charger to cool down.

3. Use the manufactures recommended fuel filtering.

Easy for me. My home marina is at the end of a small harbor, all of which is a no wake zone. I am a nm from the harbor entrance. A no wake speed for me is about 4 knots. So it takes me at least 15 minutes to go from the dock to the exit the harbor. Often closer to 20 depending on how long it takes to toss lines and how much traffic (ie kayakers, SUPs, and silly weekend boaters) is in the harbor. So the warm up and cool down takes care of itself.

My engine has a rated hp of 380 at max RPM of 3,000. In sea trials, I can make about 2,925 rpm at max throttle. Fuel consumption is about 20 gph at max. I normally run the engine at around 1450 rpm at a fuel consumption of ~2.2 gph. At that rpm, my engine is only delivering about 165hp.

The point is that most of the time I’m operating my engine at a relatively small percentage of its rated power. So even if I didn’t have the longer warm up period, I wouldn’t worry about powering up to my cruising rpm after 5 minutes of running. If I had a planing boat and ran the engine hard, it would be different. There are other decent reasons for periodically running the engine up to a high power setting. It allows you to check the performance of the engine and look for potential trouble. However, I don’t think it will make any difference as far as keeping the injectors clean.

Cummins calls for 10 micron primary and 2 micron secondary filters. That is what I use. However, this last time I only had 2 micron primary filters available to that is what I put in this time around. Vacuum is still just 3 inHg. Sure, I could add another filter ahead of the primary filter, but in my area I have never run into dirty fuel. I’ll continue to do what the manufacturer recommends.

As for fuel tanks, I never worry about condensation in the tanks. I’ve never had any water in the Racor turbo filters. I have had less than 1/2 tank of fuel in the tanks for much of the last year. No water. My last sailboat had a 50 gallon tank. It would typically get filled once a year in the summer. No water in the fuel in that boat either. Personally, I think water contamination in fuel due to condensation is largely a myth for our types of boats.

FWIW, I’m completely ignorant of all things engine related. I’m not a diesel mechanic nor an engineer, so I will accept what the manufacture and highly qualified mechanics have told me.

Edit: Forgot to mention the polishing issue. I have never had any fuel related problems here in the PNW and SW BC. A common rail engine returns a huge amount of fuel to the tanks. So any time I am running the engine, I am filtering a lot more fuel than I am actually burning. In my case, any additional filtering would be superfluous. I also have never seen the need for testing or filtering the fuel before I take it on. However, not all regions of the country/world are as fortunate in that regard.

 

[DDW]

My engine has a rated hp of 380 at max RPM of 3,000. In sea trials, I can make about 2,925 rpm at max throttle. Fuel consumption is about 20 gph at max. I normally run the engine at around 1450 rpm at a fuel consumption of ~2.2 gph. At that rpm, my engine is only delivering about 165hp.

You are babying it more that you think. At 1450 rpm the engine is *capable* of 165 hp, but the prop can only absorb a small fraction of that. The 2.2 gph suggests it is actually making about 42 hp. If you look at the Smartcraft display it will give torque output as a percentage of max at that rpm, I'd guess you'll see about 30%. 30% at about 1/2 max rpm = 55 hp. So somewhere in that range.

I have the same engine in my AT34, usually run it at 1300 or 1350, 1.9 g/h.

 

[BandB]

Since I am new to larger Diesel engines, I have asked similar questions.

My boat has a turbo-charged Cummins 5.9L QSB engine rated at 380hp. Unfortunately, I have the opportunity to spend some time with a very experienced and senior Cummins mechanic. I asked him some of those very questions. This is what he said.

1. Start up and make sure the idle is smooth. Then leave the dock. Allow the temps to rise to close to normal operating temps before adding a lot of power.

2. Don’t bother with short periods of high power. He said it was good advice for order engines, but not necessary for modern electronic common rail engines.

3. Give the engine a short period of low speed running before shut down to allow the Turbo charger to cool down.

3. Use the manufactures recommended fuel filtering.

.

I will consider the second #3 to be #4.

I agree that's a good list. However, I still believe in varying speed and occasionally opening up to higher speeds. Now the importance of that varies with engine and with potential desires. Not talking large periods but over a 6-8 hour day at least 5 to 10 minutes of other speeds. I believe the same for someone normally running at 75% loads, to run at other loads some, if for nothing more, just to see if any issues. Opening it up will show you things that you wouldn't know at 15% load. On the other hand if you run at 75%, you may discover some things needing attention when you run a bit at 15%. If you only run at one speed or a narrow range, then you won't learn as much about your engine's condition.

As to #4, I agree with manufacturers' recommendations on filters and nearly everything else.

As to having a polishing system, they can be useful on a high hp and performance type boat. However, they're not generally necessary on recreational boats. Perhaps if you cruise in central and south America a lot. I will tell you what I find more beneficial. That is testing fuel at filling, especially if adding 60% or more of your total capacity. I think having internal polishing like Alfa Laval was more important before the wide availability of instant fuel testing. Also, at oil change, in addition to testing your oil and other fluids, have your diesel tested. This will indicate if you have potential problems developing.

 

[North Baltic sea]

Hi,

I have a Cummins 5.9 qsb marine engine 2009 and it reaches max rmp 3065 which is perfect my Nordic Tug 37.

I have read a lot of conflicting opinions on the engine to run at low rmp a long time, because the machine may damage the carbon and etc. Some say it's ok to run this type engine at low rmp if the coolant remains in the correct slot.

The time i run my engine is most often 850-1300 rpm since the boat is most economical in this rmp area and temperature is ok. Cummins runs fine and does not smoke any, exhaust pipe mouth environment does not show any black carbon.

What is the manufacturer's view of low load low rmp almost always, whether it is ok or damaging the engine?

It would be great to have an expert answer, all the web instead of rumors.

xxxx


Cummins say:

Xxx
This is fine for our engines. It is not suggested to Idle (650-750rpm) for long periods. Generally speaking, you can idle for about 20 minutes or so at this range and be okay. If you plan to idle longer than 20 minutes or so it is suggested that you ramp up your RPM to about 800-1000. Working the engine under a light load/rpm is fine. This is not uncommon for some our engines (like Generators which normally work at 1800 RPM or less) and will not cause any undue harm.
Thank you for contacting Cummins.

Xxxxxx


Customer Care Representative
If we have misunderstood the information in your communication or you have additional questions please feel free to respond to our support staff by e-mailing support.engineparts@cummins.com or 1-866-CUMMINS (286-6467). If you are located outside of North America, you can reach us at 1-615-871-5500.

NBs

 

[Hippocampus]

Some good posts here and thank you. Waiting on surveys including a Cummins QSC 540hp engine. Will take a careful look at the aftercooler and turbo as hear these are solid engines but for all common rails these maybe the places the P.O. may have left you future troubles. Wife has us convinced our ocean crossing days are over. She is sick of “life on a slant” and wants a Seakeeper so she doesn’t spill her tea.

 

[catalinajack]

Here is what I do, two big filters before the on-engine filters. The first is a 20-micron pre-filter. I consider it a polishing filter. The second is a 10-micron filter. No need for a polishing system. Monitor the vacuum gauges and change filters (five minutes, no mess) as needed. Get a bad load of fuel (rare)? That huge 20-micron filter will last a long time before it plugs up giving plenty of time to change it out at leisure, IF you are paying attention. Need lower micron final inout? Add a third filter in succession or substitute a 2-micron for the 10-micron second filter. Simple, effective, and long-lasting.

 

[OldDan1943]

consider the Reverso fuel polishing system.

https://citimarinestore.com/en/fuel...-fuel-polishing-system-150-gph-fps150s25.html

I have one. Nice clean installation.

 

[Portage_Bay]

Unfortunately, I have the opportunity to spend some time with a very experienced and senior Cummins mechanic. I asked him some of those very questions. This is what he said.

1. Start up and make sure the idle is smooth. Then leave the dock. Allow the temps to rise to close to normal operating temps before adding a lot of power.

2. Don’t bother with short periods of high power. He said it was good advice for order engines, but not necessary for modern electronic common rail engines.

3. Give the engine a short period of low speed running before shut down to allow the Turbo charger to cool down.

3. Use the manufactures recommended fuel filtering.

This clip from dhays post #19 says it all. The engines used in our recreational boats are marinized auot/truck/equipment engines. They are designed to just start and run. The fuel control system of injectors timing etc on a modern engine is very sophisticated engineering. It doesn't deliver too much fuel at lower speeds and loads. The metalugy of the pistions and rings coupled with well engineered lubrication systems doesn't gunk up the works. In other words there is no need to run WOT or anywhere near it to "clean out the carbon".

OP asked for specifics on where we get our information. Mine comes from the MTU operators training by factory reps on the MTU 4000.

Yes fuel cleanliness is critical. For those operating in North America or any other place in the world with dependably clean fuel beyond good filtration it's not a major condern. There's some excellent reading on filtration by Tony Athens on Seaboard Marine www.sbmar.com.

I get the sense that OP will may be a world traveller and may encounter issues with fuel cleanliness and water in the fuel. In those cases, and if the boat has the room, I am a huge fan of day tanks. Fill the storage tanks from the supplier. Fill the day tank from the storage tanks through the best filtration and water removal you can fit. The day tank and therefore the engines only see polished fuel.

Further refinements if the boat can be set up this way are to place the day tank a bit higher than the fuel input point of the engine so that it is a gravity feed in the event of loss of pumping power. Also aids in priming the on engine filtration. If power and room are available the day tank system can be engineered to be full time polishing. The supply pump from storage to day tank runs 100% of the time the engines are running with a generous return line from day tank to storage tanks. I am experienced with such a system on a boat designed for remote work. The day tank never runs dry engines only see constantly polished fuel. The primary and secondary filters are changed "just because" never showing any contimation.

A final note on common rail. Common rail has been around for over 100 yrs. It's the electronic controls and modern injectors that give the mondern engines the ability to easily handle varying loads and speeds without issues. https://en.m.wikipedia.org/wiki/Common_rail

 

[DDW]

The weak point of modern common rail engines seems to be the high pressure pump (some running at 30,000 psi) and the piezo injectors, which are particularly sensitive to water in the fuel. This has plagued the light truck market. So pay attention to filter changes, use a water block type filter, and do not use additives that emulsify water.

 

[Hippocampus]

DDW could you please expand your comments.

Which additives you prefer and which you steer away from?

 

[DDW]

This is all gleaned from the truck forums and experience. The Bosch high pressure pump, particularly the Va-4 and to a lesser extent the Va-3 is extremely sensitive to any water in it, self destructing and sending detritus through the fuel system ruining the injectors. On a Ford pickup, the repair bill is around $10K, you know it happens frequently because there is a Ford p.n. for the kit of parts required. This is also happening on the Duramax (Isuzu) and less often the Ram (Cummins) engines. All of them use the Bosch pump and injectors.

The consensus is to avoid (and Ford specifically warns against) any additive that claims to disperse water, or has any alcohol in it as that makes the water more soluble in diesel and helps get it by the filters. Some additives claim to condense water from suspension - which would be good because large droplets are easily filtered - but I don't know if I believe them.

How applicable all this is to a marine diesel is unknown (to me anyway) but the QSB5.9 in my boat is nearly identical to the RAM pickup engine of a few years back, and the QSB6.7 is nearly identical to the current RAM pickup engine. Marine diesels usually have better and more filters which has got to help. The Racor 500 and 1000 filter elements come in AquaBloc form, this has a hydrophilic coating that is supposed to help reject water - but Racor warns that this coating ages and you should not use them more than a year old.

I've not heard of a bunch of problems on the marine Cummins, but I'm not eager to experience them first hand either so I change the filters with fresh ones regularly, and don't use additives that aren't forthcoming about their ingredients. The only ones I use in the boat are BioBor Jr (a fungicide) and Enerburn (a metal based fuel borne catalyst). The former to control bugs and the latter to reduce carbon soot. Both of these have independent published scholarly scientific studies to support their efficacy, most fuel additives do not and are more in the snake oil category.

 

[OldDan1943]

How long to run the main engine and generator before leaving the marina?
Check the oil and coolant levels, start the engine and generator, check for exhaust water flow, shut down shore power, put the electrical load on the generator, recheck the engine temps and oil pressure. Pull in shore power cables and water hose. Untie and leave the marina. This should be more than enough time.
Coming in, reverse order, that should be enough time to cool the turbo down etc. Shut down the main engine and generator.