day tanks- opinions

I'm taking an informal survey to see how the sub-60 foot yacht owner feels about fuel day tanks.

I realize that on this size boat, day tanks are a bit rare, but I suspect some do have and use such fuel transfer schemes and feel they are worthwhile.

Ultimately, I tend to think these are perhaps less common than they should be, and want to hear counter views. TIA.

PS: occurs to me that a good number of yacht owners don't know what a day tank is. Here are the characteristics:

A fuel tank that is not filled through a deck plate, but instead pumped and filtered from a larger onboard tank(s), that in turn, is filled by external transfer, usually at the time of purchase.
Reason for existence: To reduce the threat of clogged filters and unexpected machinery shut down.

On many boats like my DD 6-71 powered boat most any brand fuel filters will be fine .

We use Raycore 1000 and a few passes ,( filter 15GPH while burning 3 GPH ), takes care of most anything.

The modern electronic 30,000PSI fuel setup gets very unhappy with marina grade .

ONLY multiple passes thru multiple good filters will assure a long injector service life.

If I had one of those engines a day tank would be mandatory if I were going out off the shelf .

Inshore there is always a tow service.

Of course for the main tanks , I would demand bailing sumps (not a fuel box) so I could check all fuel a day after filling.

We have two 425 gallon tanks, and then a 150 gallon tank centerline. I know another GA 53 owner who used that center tank as the day tank. However it does have a deck fill as well as being on the fuel transfer system.

My plan is to fill it in the US when I fill the other two, but not draw from it. Then if I need fuel in the islands I will top up the other two, always keeping the smaller tank in case I get bad fuel. It can get me to someplace I can get things corrected.

Don't have one and don't need one. I have never had fuel problems here in the PNW. Not saying it can't happen, but it just hasn't happened yet. I have 2 x 200 gal tanks and not a lot of room to add a day tank anyway. I rely on tanks that are in good shape, good fuel, and dual filters.

Sub 60 footers?

That is huge.

There are some gigantic 55 to 60 footers that carry enough fuel to consider da tanks..and dozens of fuel related systems almost never found in the 40 footer range.

It is less about boat size and more about tankage, power plants, fuel systems as a whole and boat usage.

You might get a wide variety of answers, but narrowing down what your real question is might be helpful.

psneeld said:

Sub 60 footers?

That is huge.

There are some gigantic 55 to 60 footers that carry enough fuel to consider da tanks..and dozens of fuel related systems almost never found in the 40 footer range.

It is less about boat size and more about tankage, power plants, fuel systems as a whole and boat usage.

You might get a wide variety of answers, but narrowing down what your real question is might be helpful.

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Yes I believe the issue gets down to total tankage. Boats that carry large amounts of fuel that sits in tanks for long periods would benefit most by a day tank fitted with high grade filtration before the tank and of course a full system polishing unit along with tank sump drains. A boat with small tanks used regularly and operating where clean fuel is readably available the extra precautions don't make sense. I believe many fish and commercial boats rely on high capacity mud type screw on filters with vac. gauges when gauge shows trouble a quick change using one of the dozen or so extra filters they carry aboard.

day tanks

I carry 800 gal in 5 tanks.

I have them all set up so I can draw from any combination or single tank as desired & return the unused fuel back to any tank or combination I wish.

Getting most all my fuel in USA, putting in biocide with every full up & running it through Dual Raycor filters seems to handle most issues I have ever run into with no on water engine stoppage.

I do not have a day tank.

Often I just have both fuel draw & fuel return set to All & that seems to work fine till you get down to the very bottom of the barrel which I seldom do.

My 2 cents.

m.

I agree w Dave.

We have no fuel polishing system or day tank.

I do, every other month or so, extract about 1/2 gal of fuel from each tank. I had several gallons of water come out once just after our repower but that was caused by yard negligence. Pumped every drop of water out w my oil changer that I use to pump fuel from the bottom of the tank.

If you're going to cross oceans or the likes of the gulf of Alaska a day tank may be a good idea. But on a need to have basis for most of us polishing and day tanks are not needed. And it violates the KISS principal.

These all seem to be perfectly reasonable inputs. Sometimes I'll latch on an event that happened in my experience and rather dwell on it. To the poster who asked to consolidate my question. Here is what happened to me.
I sustained a twin engine shutdown with only a few moments between. They fed from the same, water contaminated tank. Way back when, I believed that Racor filters blocked water. They do not. They separate water, up to the time they are full. Then, they pass water. I had water filled fuel lines all the way to the engines. It was a mess to fix on the water. I did not have the Racor water sensor. Lots of learning.

I also was aware of a large yacht casualty that ended up on Hillsboro Inlet rocks, some years ago. The story was all good until the vessel hit the 2 - 3 meters seas just outside the inlet. Water stirred up in the fuel and with not even enough time to anchor, the boat was on the rocks.
Another double engine failure.
Another near casualty was the ocean tug pulling the NASA shuttle fuel tank. In some seas, with lots of fuel filter changes, they almost lost it all on Bethel Shoal, if it were not for an oil tanker rescue. A double engine failure at a bad time.

All of these particular failures could presumably be mitigated by a day tank. Now, I realize that using such a system is more work. Another tank, a new pump, a set of filters, etc. A smaller tank could have warming issues with the recirculating engine fuel. But, every time we shoot a not so favorable inlet, we are now stirring up the tanks. Tanks that could have been growing biowaste, water, and all sitting comfortably just below the pickups.

All input is good. I'll be shopping for a different boat in a few years, and really don't have a feel for which, if any 40 footers have a day tank. Thats my purpose here.

Those situations as you describe show a LOT of water in the fuel. I have never had problems with water in my fuel, even with lot of years of surface deck plates on my sailboats. I wasn't terribly good about replacing the O rings either. My current boat has fills that are not only angled somewhat they are are protected from the weather.

I think it comes down to understanding the problem that a day tank is intended to address, figuring out whether that's a risk for you given your boating practices, and whether a day tank or lots of filtering is the more practical solution.

Our boats take on fuel and burn through it on a regular basis, and our boats pretty much all have multi-stage filtration to protect the engine and keep it running under most circumstances. The problem, I believe, is when normal circumstances turn into abnormal circumstances, and I think that happens one of two ways:

1) You take on a load of bad fuel, and your otherwise clean supply of fuel turns into a dirty supply of fuel. Your filters start plugging up in minutes or hours rather than months or years.

2) You have accumulated crud in the bottom of your tank, but it conveniently stays at the bottom out of the way of normal fuel flow. Then, you find yourself in exceptionally rough seas, and all the crap that used to live benignly at the bottom of your tanks begins to get stirred up. Once again, you filters start plugging up in minutes or hours rather than months or years.

In both cases, there are fundamentally two ways to deal with it.

1) Carry lots of filters, and just keep changing them. The hope is that the process of filter changes doesn't place you in any danger, and that you have enough filters to clean up the fuel before you run out and stall for good. Taking care to buy clean fuel, drain water and gunk, etc. all help minimize the risks of this ever happening.

2) Protect against the problem in the first place with a day tank. Ensure than nothing other than filtered and transferred fuel ever goes into the day tank, and run your engines (with normal 2 stage filtering) from the day tank. This prevents contamination in your big tanks from getting into the day tank, and shields you from the two risk factors above. But it's not free of all risk. Crud can still accumulate in your day tank, so it needs to be maintained just like any other tank. The advantage is that it is much smaller, so if accumulated crud does get stirred up, it takes less filtration to clean it up, so fewer filter changes before you are running clean again. Also, if you have crap in your main tanks, it has to be filtered while transferring it to the day tank. So you will consume filters making the transfer. But the advantage is that it's a single pass transfer, where without a day tank your engine is circulating lots of fuel continuously so will plug filters faster. And another advantage is that you can change any transfer filters at your leisure without engine shut down.

So I really think both are viable strategies to keep your boat running when faced with bad fuel. There are arguably advantages to a day tank, but it comes at the price of an extra tank, transfer pumps, extra filters, and more complex operation. But unless you are doing serious open water cruising, I don't see it being a worthwhile feature, and very few sub 60' boats are doing serious open water cruising. And plenty of 60' (give or take) boats doing open water cruising do NOT have day tanks and survive just fine. By way of example, the Nordhavn 55/60/63 boats like mine are NOT set up for day tank operation, and they regularly cross oceans. With some minor equipment and operational adjustments you can run with a day tank, and that's what I've elected to do, but 95% of the fleet do not, and just rely of keeping their tanks clean, buying fuel from reputable suppliers, and carrying lots of filters just in case.

I have basically the same tank configuration as Menzies. Even though I just had the tanks cleaned, I do plan to use the centerline tank as a day tank and see how convenient that turns out to be.

angus99 said:

I have basically the same tank configuration as Menzies. Even though I just had the tanks cleaned, I do plan to use the centerline tank as a day tank and see how convenient that turns out to be.

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I think if I had a third centerline tank as you do, I would use it as a day/weekend tank as well.

My fuel capacity is 1240 gallons. That includes port and starboard day tanks of 100 gallons each.

My reason for adding day tanks when replacing my tanks was that I anticipated occasional refuelling in remote areas, possible from drum fuel. So far I have not done that. Nor have I had any fuel issues.

Normal fuel pickups are a bit above bottom of my tanks. But the polisher pickup, and there is polisher pickup in all 6 tanks including the day tanks, is only 1/4" from the bottom. So its going to get most of anything lying at the bottom of the tank.

Well, with 5000 gallons through the system I'm still on the same Racor filter in the polisher and its vacuum gauge reads fine. No water in the bowl either. But I've only filled at high volume marina's in USA or Australia, where fuel quality is very good.

Not to hijack the thread but do you take a fuel sample at the fuel dock before refueling or just go right away? I had an advise to always carry a glass jar to first take a sample and have a look at it first, I found this wise.

Lou_tribal said:

Not to hijack the thread but do you take a fuel sample at the fuel dock before refueling or just go right away? I had an advise to always carry a glass jar to first take a sample and have a look at it first, I found this wise.

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I'd be concerned that if I did that at my local fuel dock I would end up wet!

for remote places using drum fuel people in the past used a filter funnel to pre screen the fuel before it gets into the tank and or stop fueling and sort out the problem.

How does one use a 100 gallon day tank on a longer trip? are you continuously filling it watching for over fill or just take the chance of running dry?

Personally if i were able to specify new tankage i would like some sort of bottom sump and drain. An access port would be nice as well.

bayview said:

for remote places using drum fuel people in the past used a filter funnel to pre screen the fuel before it gets into the tank and or stop fueling and sort out the problem.

How does one use a 100 gallon day tank on a longer trip? are you continuously filling it watching for over fill or just take the chance of running dry?

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It feeds from the main tanks. You can use the fuel transfer pump and fill it on a regular basis.

Posts 15 and 18 are well reflected in Nigel Calder`s writings. Not hard to squirt some diesel into a jar to check for junk and to see if the "bubbles" disappear.
Brisboy recently replaced the drain screw plugs of his tanks with valves, a smart idea.

bayview said:

for remote places using drum fuel people in the past used a filter funnel to pre screen the fuel before it gets into the tank and or stop fueling and sort out the problem.

How does one use a 100 gallon day tank on a longer trip? are you continuously filling it watching for over fill or just take the chance of running dry?

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I normally fill the day tanks in the morning before setting off for the day's run.

At cruise speeds I'm using around +/-3 gph per engine, less if I'm in no rush. So 100 gallon day tanks for each engine is plenty for a daytime run. Were I going to run overnight or for a few days non-stop then I would probably just open the tank inter-connectors between the day tanks and the lateral tanks assuming I was filling at reliable sources. The fuel return is warm so I would not want to run the day tank too low or fuel temp might start to become an issue.



A filter funnel makes sense for occasional drum fills. I'd re-think the system if I was going to be using drum fuel a lot. Perhaps have a polisher pickup line that went to the drum?

I have two 20 gallon tanks. Only the port tank has a fuel fill. The starboard tank is filled by pumping through one of my Racor filters using a dedicated transfe rpump. I run off the starboard tank using my second Racor. 20 gallons of fuel is about 40 hours run time at my normal 6-6.5 kt cruise speed.

My fuel manifold lets me select either tank and either Racor. I can also select which tank to return fuel to. Consequently, my full 40 gallons is available (i.e., ~80 hours run time).

I think "day tanks are an unnecessary complication on a smaller yacht, IF you have good filtration and monitoring of fuel. I don't think its necessary to have a fuel polishing setup if you have tank cleanout ports and they are used. The SBAR (Tony Athens ) setup is first class and makes clean fuel easy. I would much rather be able to open tanks from time to time than have a blind guessing game and a "polisher" system. YMMV, my opinion only.

I carry 16,000 Gals in 10 tanks, my first centerline tank is approx 2650 Gals and is a dedicated day tank, and is the only tank with engine suction and returns. Under normal cruising I top off twice a day, each time I'm on watch. But we're a bit bigger than 60', lol.

ps: I also have a dedicated clean oil tank (420 Gal) and waste oil tank (420 Gal) each with it's own gear pump and deck cam-lock connection.

In your situation a day tank is almost a neccesity . The tug I run has 16,000 gallon day tanks and a 90% fuel capacity of 220,000 gallons, I still wouldn't want a day tank setup on a small boat. Unneccessary in my opinion. Why look for complications? Modern fuel filtration takes care of fuel cleanliness .

Sailor of Fortune said:

In your situation a day tank is almost a neccesity . The tug I run has 16,000 gallon day tanks and a 90% fuel capacity of 220,000 gallons, I still wouldn't want a day tank setup on a small boat. Unneccessary in my opinion. Why look for complications? Modern fuel filtration takes care of fuel cleanliness .

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Can't remember the exact date, I think maybe mid to later 90's, I took a 255' ice class tug across the Atlantic, she held a LOT of fue tool.
On the aft deck area, as the hull sloped up over the props, someone had cut the top off one of the tanks, lined it with tile, and it made a perfect shallow to deep swimming pool, LOLOL

Sailor of F: Interesting perspective. Why do you suppose large vessels have day tanks? I'm not familiar with the regs of larger boats, but I'll suspect insurers like Lloyd's, etc are driving this, if not them then maybe det norske or others. The chance of failure of the larger boats is likely no higher, but the consequences are. Certainly these boats can employ centrifugal water separators that small boats can't.
Bottom line; would you think that the use of a day tank on smaller boats makes the system more or less reliable?

I can tell you that on ships that run on heavy fuel oil, the day tanks are heated to boil off water and the make the fuel more viscous and easier to inject into the engine. This is done in the day tank so that there is no requirement to use huge amounts of energy to heat the main fuel tanks. On tugs and other workboats it is a place to store the fuel that has been prepped for use by running it through a centrifuge.
If your fuel is not going to be treated on board in some fashion prior to use, there is no real need for a day tank. However, if your vessel has a fuel treatment or cleaning option and you carry large quantities in individual tanks then a day tank is a good place to hold your treated fuel prior to use.

diver dave said:

Sailor of F: Interesting perspective. Why do you suppose large vessels have day tanks? I'm not familiar with the regs of larger boats, but I'll suspect insurers like Lloyd's, etc are driving this, if not them then maybe det norske or others. The chance of failure of the larger boats is likely no higher, but the consequences are. Certainly these boats can employ centrifugal water separators that small boats can't.
Bottom line; would you think that the use of a day tank on smaller boats makes the system more or less reliable?

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I believe day tanks are a throwback to the old freighter etc days with bunker C fuel. In storage tanks, especially in colder climates, bunkers had the consistency somewhere between molasses and liquid road tar. You'd have to pull the fuel up into heating and settling tanks, heat it with residual waste heat from the boilers and let the crap separate out by gravity once it became fluid. Then transferred, clean, into the "day" tank to burn from.

I have a friend who had a Nordhavn (47?), on his trip from Santa Barbara to Cabo his engine stopped. He had gotten some bad fuel from the marina in S.B. and for reasons of pure laziness, on this longish passage had gotten tired of moving fuel through the filters to the day tank, changed his routine and let the fuel go straight to the engine. Killed his wing engine too. He spent a very bad night in swells trying to get the crap out of his engine so he could continue.

Day tanks are a very good solution to cruising - who would ever expect bad fuel from a large port like Santa Barbara? Just keep using them!