Diesel Gunk Reality Check

[Microship]

Hi from S/V Nomadness, a steel Amazon 44 PH cutter with Yanmar 77HP turbo diesel, Yanmar 7.5 KW Genset, and 240 gallons in 3 tanks (one of which has been cleaned by the previous owner with the intent of repurposing to water). There are dual Racor 500s, and an on-board polishing system.

While trying to figure out the state of sending units to interface the Maretron tank level adapters in order to get better fuel level data than the useless old gauge shared by all three, I excavated my way past an ancient watermaker to one of the wing tanks. I opened the inspection plate, inserted digital camera, and did a panorama of the grim little scene, a couple of highlights of which are below. (More commentary and another photo are in my blog post on the subject.)

I've read with interest the threads here on related topics and am slowly accepting the likely answer, but I thought I'd ask advice of the cognoscenti on this forum. The tanks have been low since I bought the boat last year, overwintering in the Northwest at about 1/3 capacity and doubtless condensing merrily on every thermal cycle. The surveyor commented back then that the fuel and filters looked very dark, and the previous owner said it had been polished a year earlier. In other words, this diesel is at least 2 years old, and the tank-cleaning history is unknown.

I haven't pulled a sample per Calder's suggestion in his diesel engines book, but I am wondering if the look of this crud tells an experienced eye all we need to know to justify getting the tanks cleaned before slurping any more of this into an expensive engine... or throwing good fuel in with bad.

The possible bright side is the third tank mentioned above - 90-gallons under the aft berth. Since I'm leaving the marina in 3 days, maybe it makes sense to confirm that is still properly plumbed to engine and not water system <shudder>, fill 'er up, and deal with the gunked-up wing tanks down the road. Advice?

Many thanks,
Steve

[Microship]

Just a follow-up on the day before departure (eek!) - the third tank is indeed still plumbed into the manifold, and I removed the sender unit to have a peek. Just a small puddle by the pickup of reddish-black stuff, which I could transfer into one of the contaminated wing tanks before a fill-up. I'm coming to the conclusion that I shouldn't use the tanks or fuel referenced above until they are cleaned and the diesel polished...

Any advice will be really appreciated... I'm new to marine diesels (Cummins in my truck, but it just works.)

Cheers,
Steve

[AnchorageGuy]

I guess I can't help but wonder why after this you would not have those tanks cleaned unless you don't plan on ever using the engine or genset?

[Pblais]

Fuel is not as pure as drinking water. It has a lot of stuff in it we all would rather not see. You might want to try a service to do this. Around here they charge about $75 / hr and it takes several hours to do one tank so you are looking at probably a full day. You can remove all the old fuel and dispose of it. They suck fuel out of the tank and pass it through a large filter then put it back under pressure. It basaically power washes the tank with the fuel. The process contiues and filters are changed out. This is far quicker than any polishing system can do. It works. You might want to bring down the fule level in the tanks to do this as it shortend the time required. The pump I saw used was a 400 gallons per hour pump. The filter was a cylinder warppped with a filter paper about 12 inches by 18 inches. The first few come out solid black as the pressure drops on the gage. They continue until the filters look decent. For three tanks it probably would take a full day and part of another.

A neighbor has a small tank maybe 20 gallons and only used to engine to go out to the race course and back. Fuel was 2 years old and looked pretty bad. The filtration allowed him to use it and it cleaned the tank in the process. All tanks get a little bit of something in them. Taking the time to get most of it out won't hurt and expecting perfect tanks is not required.

[Microship]

Paul - thanks. I just needed a voice of experience to confirm that this is indeed an issue... having never seen inside a diesel tank, I wasn't sure if I was over-reacting to the gunky stuff. I'll use the 90-gallon clean one in the near term, and find someone to do the job on the 75-gallon wings.

Chuck - I'll definitely have them cleaned. It was a bit of a shock to peer in there (after removing the huge old ASC watermaker to get to an inspection port... BAD design!) and discover something other than shiny stainless with and amber fuel. I just posted here to get a second opinion from folks who have dealt with this stuff before (my last boat was a trimaran with a new Honda gas outboard, and before that a homebrew pedal/solar/sail trimaran... so big industrial-scale diesels and their associated plumbing are a bit alien to me).

Thanks, folks...
Steve

[Zach]

Hi Steve,

2 years really isn't that old of fuel. I've got 5 year old heating oil running through my tractor, and 3+ year old fuel in the tanks of a trawler. If you are used to the green tinted road fuel, the red tinted heating oil/off road stuff really looks like pond scum. It'll clean up. It'll burn... though she may smoke a little more than with fresh stuff. You are home free if she smells like diesel still. That tank looks quite clean, at least on the top half. Is the clean out opening big enough to be useful? Does she pull from the bottom of the tank, or an outlet an inch or two off. (If she pulls from the bottom you probably have a day tank somewhere to drain off the water...)

Have you fired her up on whats in the tanks? Your Racor 500's are up to the task if you've got some 2 micron filters in them. Do you have vacuum gauges on the filters? (Helpful to know when to worry about the black goo, and when to prepare for open filter surgery on the high seas!)

Sounds like you have a transfer pump on board. Do some studying of the Racors arrangement and see if you can easily plumb them to polish the fuel. (Save some cash on building another rig... though will probably have to prime the engine afterward unless you have a valve hidden somewhere!)
If I were in your shoes I'd close the valves on your two wing tanks. Hook up your transfer pump to a piece of copper line. Poke the bottom of the tank and pull it back out two inches or so and tape/tie it off. Find something else to do for a while... till you get to the last two inches. Then either disconnect the filter from the system and pump it into a bucket/drum, or pump through the filter into a bucket and see if its cleaned up. Now with your copper stirring wand... stir it all up. Take the slime and filters for disposal. Pump back over, and do the same with the other tank.

If you don't have enough room in the wing tank I'd source an empty oil drum (Hydraulic oil will do fine) rather than filling up the third tank with questionable fuel.

Change her filters, not just the racors but whatever spin ons may be on the engine. By this point you've filtered out all the particulate that can damage her inner workings. (hopefully without having bought stock in Racor... Grin)

Now go out and find some rough water to get everything all stirred up. When you come back, pump from one to the other and back again. Then run her as low as you feel comfortable with what you have, and finally fill her up with a decent confidence that the next time its rough she won't clog up the filters. (See if you can find a home heating oil truck that will deliver to the dock... or if you can lay along side a fish plant/ice house to get diesel from the commercial guys... less than the bend over marina prices.)

Northern Tool and Equipment Portable Generators, Grounds Maintenance, Lawn Mowers, Pressure Washers | Northern Tool + Equipment has decent pricing on other filter mounts and pumps if you feel inclined to build something. (Being a farm boy... I like racor, but the marine prices are NUTS.)

Nice blog by the way!

[Roy M]

Pump it out into a storage container, open the tank and hand clean it, filter the stuff in the storage tank back into its normal home. Repeat for all other tanks. Then use the fuel up before adding fresh fuel to the batch. Put a Racor vacuum gauge in the intake side of the fuel pump to see if the filter being used is crudding up. If so, switch to a backup filter while exchanging the first. Woops! Pylasteki beat me to the thread.

[Microship]

Thanks for the detailed and thoughtful response, Zach!

Since my post, I peered into the mostly empty aft tank (recently cleaned), and saw just a little red/black puddle near the pickup. I used my transfer system to slurp that through a Racor toward one of the dirty wing tanks, and watched a little sandstorm raging inside the Racor bowl. Tomorrow I'll fill the aft tank, pump a little more out to further flush the lines, then switch pickup and return there until I can get the wings cleaned. I also just connected the Maretron Tank Level Adapter to the resistive sender, so might have some meaningful data about fuel level.

Partly because of your nudge in that direction, I also just ordered two vacuum gauges from a fellow on eBay to replace the T-handles on the Racor 500s. Things might get dirty while I'm messing with all this... still haven't changed them (it was done just before purchase) but I'm sure the one I just used for transfer is ready.

As to your questions... I am not sure if the pickup is in a sump, at the bottom, or a little up... can't see through the dark fuel. But with the top half being clean, maybe I can just pull from up there!

I have run the boat on one of these tanks, both for the initial delivery and a more recent jaunt (maybe 30 miles total). A little smoky, but not so much when fully warm. But it did sit all winter in the Northwest with lots of headspace in the tank, so I expect recent condensation.

The fuel plumbing is nice. The transfer pump can be switched in and out between the two buses, I can swap Racors, and any pickup or return can be selected... photo of some of it is below. There is also an oil-changing system with a similar set of valves, pump, and two tanks monitored by a Tank Tender.

Anyway, off to the boat - thanks for the other thoughts and advice... and for the kind words about the Nomadness blog! And thanks also, Roy, for the advice... looks like the gauges are a must. Anyone make an N2K version for us geeks? (Speaking of which, I'm about to add a Floscan.)

Cheers!
Steve

[Roy M]

Steve, you might consider installing the vacuum gauges in the cockpit, using a tee off the intake side of the fuel pump, and vacuum hose. Additionally, Racor makes a vacuum switch (in line with the back of the gauge) to set off an alarm/idiot light above my gauge, when things start to get blocked up. It allows me to switch over to the other filter before the engine shuts down, which generally has happened as I am about to enter a rough inlet where there would be no time to switch over before crashing into the rocks. Yeah, I am paranoid about the fuel, but then I've survived some near disasters....

[Microship]

Roy - thanks... that's good to know! I bought one gauge per filter; sounds like your method uses just a single one on the hose and looks at whichever one is currently in use, which makes much more sense as I'm only using one at a time anyway <smiting self on forehead>. Since I have a tendency to over-engineer everything, maybe I should put a video camera down there now... ;-)

The gauges I bought are eBay item 300183329711 - do these incorporate the idiot-light interface (and is that a preset limit)?

Cheers,
Steve

[Pblais]

It allows me to switch over to the other filter before the engine shuts down, which generally has happened as I am about to enter a rough inlet where there would be no time to switch over before crashing into the rocks.

It takes a while for a filter to go totally bad. You have a while so the alalrm would make it easy. You'll see the rpm's go up and down, but not quite as up as it was before. It's almost a sure sign the filter is about to give it up.

[Roy M]

My experience with diesels shutting down from clogged filters has been a bit more abrupt. Typically I have heard the oscillation in RPMs, and as I rushed to get to a filter bank (if something like that existed on the boat) the engine would stop. Then there was the problem of possible air in the line from the other unused filter, the interminable bleeding and false starts, etc.

The Racor system solved this for me, and that's why I try to get my customers to install them. Simply having a gauge in the cockpit means you can be regularly informed of the status of a filter. Is it beginning to move into the yellow zone? That's not normal. Am I in a location where a fuel shutdown could ruin my whole day? Then I can switch early, BEFORE a potential problem ensues, even correct an air bubble problem (Murphy's Law hasn't been repealed yet) prior to an approach. You can also install another vacuum gauge in the engine room using another tee in the line leading to the fuel pump input.

The Racor vacuum switch is simply screwed onto the back of the vacuum gauge (or anywhere else convenient in the vacuum hose), and the two wire leads directed to whatever idiot light, buzzer assembly or relay you choose to use. Mine is set up to announce, via a buzzer unique to the alarm (Radio Shack has many different sounds available), that a pre-set vacuum has been reached. At the same time, a light turns on above the vacuum gauge. The scenario: I'm asleep, the inexperienced watch hears the buzz, looks down at the instrument panel, sees the light above the vacuum gauge, notes it is in the yellow (or red, by that time?) zone, and calls for someone to assist giving the specific information that the fuel filter gauge has gone off. Hopefully, I am roused from deep slumber and able to switch over the filter bank in my semiconcious state.

The truth is, though, with all of these systems in place, and the monitoring of the fuel filter status regularly, the likelihood of an unexpected problem probably plummets. Such is the danger of preparedness - your safety procedures reduce the likelihood of surprise and failure. And it lets me sleep more deeply off watch.

[Zach]

The air bleeding after the filter has plugged, has to do with the level of vacuum being pulled on the fuel. The vacuum causes the fuel to boil. Then you get vapor lock. The pump can compress the air bubble, and which causes the flow through the pump to stop...

If someone was really on their game, (Or had a boat that really pissed them off... ) they could build a set of solenoid valves to switch filters, triggered by the vacuum alarm or a switch at the console. Would be fairly simple... but I'd like to see manual valves as backups! Likewise, a relay to the shutdown solenoid would be pretty easy to set up to kill the engine prior to reaching vapor locking vacuum. Would at least speed up the time from dead engine to back in business on boats that are prone to that problem.
(I haven't tested to see how many inches of mercury it takes to boil diesel... )

I'll stick to just watching the gauges on the half hourly engine room check. A little bit of pro-active solves a lot of problems before they happen.

[markpj23]

Gee... I wish TREKKER's tanks had looked that clean... but no longer my issue.

Much discussion in other threads about what size filter element you really need in the Racors. IMO don't waste the 2 micron elements in the first filter in the path. 10 micron is just fine and the engine filter 2 micron typically is all you need to protect the engine. Do a search in the Engines threads....

Great that you have a polishing setup - that's going to earn its keep.

[Roy M]

Steve, since you are familiar with video systems, you will appreciate how handy your idea really is. I intend to install several cameras for other purposes, but the one in the engine room is definitely one of them. It beats having to open the door to the heat and din of the engine just to eyeball that all is fair. My Raytheon E120 system allows several video inputs to the displays. And, as you know, they are pretty sophisticated and not too costly for those applications.