USUABLE fuel capacity?

[Bob_Lee]

I have an Albin 32+2 with two 130 gal. tanks with the crossover hose that is always left open. I was fishing at sunset last year and shortly after dark headed for home. The genset was running and the boys were watching the ballgame. The 370 hp Cummins died and I dropped the anchor. The genset continued as the Sox were winning. I had about 3/16 showing on the fuel gage. Thinking it was the filter, I changed that and still no go. The genset was still running. Towboat US was quick to respond and towed me from the Jamestown Bridge back to Tiverton Harbor. (Good job guys!) The genset ran all the way home.
The next day I had Ken look at my engine. His "repair" consisted of topping off my fuel tanks with 198 gal. of diesel fuel. I still had over 60 gallons of fuel on board, plus the diesel genset still was running at that level.
Does anyone know how much "unusable" fuel should remain in the tanks when the engine will not feed anymore?
Is there a fix to get better usage?
Thank goodness I paid my $125 to Towboat US, the tow would have cost over $900.

[Mariner]

I had a similar experience in our 36' Express Trawler. I didn't think much of it, but when I thought about it later, the fuel gauges on both tanks had been showing about 3/16 of a tank for some time. Thinking we'd just been conserving fuel, I headed out for a day of crabbing. Unfortunately, just as we were entering the harbor, the engine died. I guess I should say fortunately, because if it had happend as much as five minutes earlier, it would have been a real problem. It was dark and the weather was bad. As it happened, we simply drifted into a neighboring marina and called my father to bring some diesel. After a couple trips to the local gas station, and humping some fuel tanks up and down the dock, we had enough to prime the engine and get home.

What concerned me the most was that the fuel gauges did not give any indication that we were low on fuel. But upon inspecting the tanks, they appeared to be completely bone dry. My thinking is that the problem is not that the tanks don't fully drain, but rather that the gauges are not accurate.

I would be willing to bet that our fuel tank setup is the same or similar to yours, so this could be a problem common to these systems. My solution has simply been to not let the gauges get below 1/2, and watch the engine hours more carefully. I would really like to recalibrate the gauges, but for now, a little extra precaution does the job.

[Tuxedo]

Coupla things -

1. Fuel pick-up for the engine is in the front of the tank, fuel pickup for the genset is probably in the rear. Bob_Lee, I bet you could have gotten the engine restarted and limped home at trawler speed. I did once.

2. The factory installed fuel gauge sender sucks. Install one from WEMA.

http://www.wemausa.com/

[Mariner]

In our boat, there isn't a fuel pickup. There is just a very large outlet fitting that comes out right at the very bottom of the tank. One on each tank, which then feeds into a day tank, which also has a large outlet fitting at the very bottom. In every case, the outlet is at the back and very bottom of the tank, and the bottom of the tank slopes towards it. it's hard to imagine that every last drop wouldn't be collected and sent to the engine.

[Tuxedo]

Mariner -

I think each different model has its fuel tank plumbed differently. They may even be different based on model year or phase of the moon. My 31 with factory installed genset has 3 tanks interconnected, and the engine fuel pickup and return in the front of the center tank and the genset pickup and return in the back of the port tank. If Bob_Lee's is similar, it would explain why his genset kept running.

My prior 31 ran out of fuel with the gauge showing 3/8. I found out the sender was faulty. From then on, it's been WEMA for me.

[Water Friends IV]

I have a 30 Ft. Family Cruiser with a specified fuel capacity of 126 gals. Soon after I bought the boat, I ran out of fuel and had to be towed to a marina which, fortunately, wasn't too far. I filled both tanks full, and it took 101 gallons, so I should have had 25 gallons. Anyway, I inquired to my dealer and the Albin factory, neither of whom had any explanation.
So now I just figure a usable a usable fuel quantity of 100 gallons, subtract 20 gallons as a reserve, and use an 80 gallon rule of thumb for my fuel planning. I've been averaging about 6.5 gallons per hour, so I plan for a maximum cruise of 12.3 hours, with a 20 gallon reserve ( plus the 26 unusable gallons.)

[Veebyes2]

Just spotted this thread & it has some recent relevance to me & my 32.

First of all marine fuel guages seem to be notoriously unreliable. Second, count on 10% of your capacity being unusable below the pickup. Third, if you have two tanks, don't draw from them simultaneously because when you run out, well, you are out with no reserve.

I recently had genny problems. The symptoms were fuel starvation. The guage read adequate fuel, I thought. Fuel filters were long overdue for a change so that is where the blame went. Still run then stop from the genny. Took the intake hose off the primary filter & blew into it. It was NOT the sound of air going into liquid.

Guage indicated just over 1/4 tank on the tank the genny draws from. Had I been at sea the propulsion engine would continue to run longer since the genny pickup was deliberately installed in the tank higher than the propulsion pickup.

Much more important to be able to get home than watch a ballgame using the genny.