How low to run fuel tanks?

Rockbottom said:

Carry plenty of spare filters and go. You have already said if you get tight on fuel you can stop at a closer marina. You should not use the bottom of your tank as a collective for contamination, it will just get higher and higher in the tank. Your filters are the antidote. Just don't run out!

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I bought five cases of filter before we left Lisbon. I've already used one half case by the time we got to Iqaluit.

ghostrider454 said:

Wherever it is I wouldn't buy it - probably more water than fuel.

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South Florida is quite busy with diesel yacht traffic and a lot of turnover of inventory. Your comment is very unlikely. Perhaps your experiences in the area you're cruising is that way.

Idea #1. Have your fuel polished and tanks cleaned before you go. I know there is no cost savings in that

Idea #2. Along the way add some higher cost fuel to be sure you get to the cheap Dock safely

Simple question, Simple answer:

Don't. (why risk it)

pete

Peter, drawing fuel from the bottom of the tank ensures that any water or crap that may be present will be drawn off in the regular course of running the engines. Therefore, dual Racors will rarely or ever be useful. Do you have or know anyone who heats their home with fuel oil? The storage tanks are always bottom feeders. Water is never a problem nor are fuel-eating bugs cuz no water. Homes go decades with nothing more than an occasional filter change. Interestingly, home heating oil which is produced and, more importantly, delivered in the same manner as No. 2 diesel yet one never hears about a bad load of fuel oil plugging up a furnace feed.

mvweebles said:

Not sure I understand the connection between bottom draw valves reducing need for dual Racors. I have bottom draw valves too and wouldn't be without dual Racors even though I've never had a fuel issue.

To the OP: you're over thinking this. Assuming you have saddle tanks, they are most likely tapered meaning 50-gallons remaining is pretty deep in the tank. Running most of the fuel out and turning it over is a good thing.

Have a good trip. Your risk profile by running light is not significantly changed. You have dual Racors and placed to duck into if you get nervous.

Good luck. Wish I were along for the ride.

Peter

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Interesting idea Jack but.. Home heating fuel is delivered to the basement, generally, and there it stays until used probably within a month during the winter. No temp change from 100 degrees on the plus side to about -30, at least here in Wisconsin. Also generally purchased from a source that delivers a thousand or more gallons a day not some hick marina with leaky tank covers, maybe a leaky tank and a volume of a thousand gallons a year. the leftover sits until next year.

I'll keep my tanks as full as practical, thanks

pete

RickyD said:

Idea #1. Have your fuel polished and tanks cleaned before you go. I know there is no cost savings in that

Idea #2. Along the way add some higher cost fuel to be sure you get to the cheap Dock safely

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I second , have your tanks cleaned. You wouldn't believe what came out of my 30 year old steel tanks.

Have four tanks to choose from to feed a single engine. Have two manifolds, one for feed and the other for return, eight valves total. Use one tank at a time. Switch tanks to even the boat's attitude. Also have a pump to transfer among tanks. ... Since feed is from near tanks' bottoms, choice is not a matter of perceived fuel impurities.

If it were I and I owned a thirty year old trawler with steel tanks, I would have the fuel polished and tanks cleaned before I did a long passage with or without Racors.

We bought a 1983 DeFever 44 six years ago and had the fuel polished before travelling home. Not a drop of water or crud even though the tanks are bottom feeders.

BigTime said:

I second , have your tanks cleaned. You wouldn't believe what came out of my 30 year old steel tanks.

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catalinajack said:

We bought a 1983 DeFever 44 six years ago and had the fuel polished before travelling home. Not a drop of water or crud even though the tanks are bottom feeders.

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Did you know your tanks were bottom feeders before you had the fuel polish service done? Is that a standard for all Defever?

How low is too low?

Having a GB32 in the Great Lakes, I keep my tanks at least a third full, but probably do not need to. Consider the weather. If you might take a threshing in a thunder storm, do not run lot. Otherwise, in reasonably calm waters it should be no problem.

What would be the rationale of never going below ⅓ full. If that were my case I'd have 90 unusable gallons of diesel.
Tanks are as a rule built with the suction at a natural low spot. You should be able to get down to about 5 gallons if you watch it close, but often sight glasses don't show the last 4 inches or so, so just quit when you can't see fuel. It would take continuing rough seas to lose suction in all but a poorly designed and maintained system..
Also, who runs with more than one tank open? Doesn't that encourage the possibility of sucking air if one tank gets low? Not to mention the free flow back and forth as someone mentioned. This practice can lead to stability and trim issues and should be avoided.
And also as a safety issue, if a line leaked or broke you'd lose everything.
If you suspect that your tanks have sludge then good seamanship dictates that you address the problem.
At thirty years a steel tank is on it's last legs unless the boat has had some exemplary care.
Certainly if it hasn't been cleaned properly it has sludge

IMO, use your filters and run the tanks down to refresh most of the fuel. Your tanks will polish the fuel in there as they run. I would want as much fresh fuel in the tanks I can get with a new to me boat.

I did not know when I had the fuel polished that the tanks feed from the bottom. This was and is our first boat and I knew very little about the boat's systems. I do not know if bottom feed is standard on DeFevers. I do know another DeFever44 owner (vintage 1984), mine is a 1983, whose fuel feed is by dip tube which surprised me cuz he also has bottom valves. I have occasionally opened the drain valves to see what comes out. Never any water and just a fleck or two of debris. A prior owner had the tanks cleaned about 15 years ago. The drain valves are actually one inch lower than the supply valves. I simply do not understand why dip tubes are used rather than a bottom feed. Of course, with dip tubes, over years of use, sediment will accumulate as will, potentially, water. I am pretty happy that I stumbled upon a bottom feeder.

Swfla said:

Did you know your tanks were bottom feeders before you had the fuel polish service done? Is that a standard for all Defever?

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10 % is the bare minimum (25 gal in each tank), do you polish your fuel, if so you should be good, if not I would probably stay at around 20%

OPPORTUNITY to have your tanks inspected internally and cleaned out. Unless you or previous owner had it done in the past 5ish years. Good luck.

Deactivated my polisher and use its pump to merely transfer fuel among tanks or to prime engine.

I don't really think of my tanks in terms of gallons (except when paying the attendant). I have sight glasses and marked them with masking tape on my first fuel fill. Put a piece of tape on and then put in 100 gallons (378.541 liters). The second piece of tape gives you the "inches per gallon" (or centimeters per liter). That and my consumption rate (gph or mpg) allows me to calculate how far I can go. The bottom is canted to fit the hull, so the last 8 inches goes twice as fast as the top of the tanks.

I don't know that how you think of your fuel level makes much difference in calculating when to fill (or when to get nervous). And I guess that one's fuel burn rate plays into whether 30% is time or 20% is scary, etc. 20% is still 200 miles for me. In most places that's not time to worry.

Fuel Polishing and cleaning at the dock

No on has mentioned having your tanks polished. There are companies the will flush/cycle the the fuel from the bottom using a dual hose the enters through the fill plate returning the filter fuel back to the tank. You could also use a suction pump and sample fuel from the bottom, maybe a few gallons to determine if you have water or other contaminants in the fuel. A few years ago I manually cleaned a 80 gallon boat tank and scrapped out heavy black material that lined the bottom after emptying the tank. The sluge filled about a 5 gallon pail. It would be best that you find out at the dock rather than underway. Many tanks have access ports that allow entry with your arm after emptying the fuel.

Interesting experience. Is that a step further than inspection and cleaned out like I mentioned?

Yesterday I learned how far NOT to drain them on my dinghy, and that's 100% of the way. Had maybe 1/4 cup in the tank. Fortunately I always carry a handheld and was able to hail the first passing boat. Oddly it was even a sailboat - with his radio on! Single handedly too - very considerate. We could have rowed but it was getting dark and the black flies were coming out!

He's in our marina and got a nice thank you gift today.

Swfla said:

South Florida is quite busy with diesel yacht traffic and a lot of turnover of inventory. Your comment is very unlikely. Perhaps your experiences in the area you're cruising is that way.

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I burn Bunker C. We got a bad load in Houston two years ago on cheap fuel. Cost us $50,000 to remove it and clean the tanks (80,000ltr) and then buy new clean fuel in New Orleans. We now also burn LNG which is far cheaper than "C" and it's environmentally cleaner. It's also why so many countries are switching to natural gas and getting rid of wood, coal and heating oil furnaces.

As I recall the OP was interested in running his tanks low so that he would have a better chance of finding "cheap" diesel somewhere in Florida. Perhaps he has already filled up by now? We seem to have passed the low point for gas and diesel here in Massachusetts, and prices have rebounded significantly from 3 months ago. So best advice is probably to fill up quickly!!.

Shrew said:

I use the first 3 on the list with every visit to the fuel pump. The last one looks interesting, however I've never used it.

https://www.defender.com/product.jsp?id=3863005

https://www.defender.com/product.jsp?id=1380818

https://www.defender.com/product.jsp?id=3862862

https://www.defender.com/product.jsp?id=2793436

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Shrew, are you actually using all 3 of these additives at the same time (with every fill-up) or rotating them in somehow?

Hi ERTF, lots of response to your inquiry. Have you made the trip? It's always appreciated by members when we hear back from a thread starter.

After Irma, I got the ‘water in fuel alarm’ but never had a shut down. I replaced the tank fill o’rings, had one of the ME Racor totally rebuilt. The other filter was unused.
During a yard visit, they blocked the boat so as to drive the water and crap aft, nothing
Finally put in a fuel polishing system.
The AT carries 400 gallons and are bottom feeders.
First thing I did after the installation was to run the polisher long enough to polish about 500 gallons of fuel.
The valuing allows to to shut the cross over and draw from the selected tank. The return is also valve controlled. I feel confident in the quality of my fuel.

Initially, ie many years ago, it was 1/3 out, 1/3 back and 1/3 ‘just in case.’
These days, not so much. I would not feel comfortable going below 1/4, by sight glass.

It depends on how you operate/ cruise. Typical distance to next fuel stop per your cruising preference, divided by actual fuel consumption per mile per your cruise engine rpm, plus the tank dead volume, plus a safety factor. Example: 90miles/4mpg =23gal + 10gal dead=33 X 1.25 = 42 gal on gauge.

My tanks are set up to allow either bottom feed or top feed. I have run the tanks dry when using top feed to check the pickup tube length. A couple times I have run them dry via the bottom feed to ensure the 4 year old tanks remain clean.

Having an electric fuel pump makes it easy; I just switch tanks when the engine starts to sputter and it rights itself within a few seconds and I continue on.