How low to run fuel tanks?

[Swfla]

Originally Posted by catalinajack

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.

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

[grandbanksbayfield]

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.

[Capt Dan]

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

[TowLou]

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.

[catalinajack]

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.

Originally Posted by Swfla

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

[slymeso44]

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%

[Swfla]

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.

[markpierce]

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

[Marco Flamingo]

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.

[DennisB1]

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.

[Swfla]

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

[BDofMSP]

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.

[ghostrider454]

Originally Posted by Swfla

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.

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.

[Chrisjs]

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!!.

[sailorjoe]

Originally Posted by Shrew

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

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

[Swfla]

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.

[OldDan1943]

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.

[bgillroy]

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.

[AusCan]

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.