Single Engine Fuel System Operation

New to us GB 42 Hull 803, Single Lehman Diesel.

Wondering what the recommended or pros/cons of operation off of ONE fuel tank at a time.

Based on my research there is a shutoff for both tanks, but only one return to STBD tank from the engine. Seems the STBD tank would fill up if you are only using the PORT tank for fuel.

Attached is a fuel system diagram.

Your assumption would appear to be correct unless there is an equalization line between the two tanks.

Greetings,
Mr. kr. I see no disadvantage to running with both fuel valves open. Doing so should allow tank equalization thus maintaining trim. Your thought of the STBD filling up if running on PORT is correct. I believe although Lehman's are reputed to return very little fuel to a tank IF you start with both tanks full you run the risk of an overflow on the STBD tank.
The only problem I can foresee is if you fill one tank with contaminated fuel, you may cross contaminate the other.

Or you could have a valved return line to both tanks and return fuel to the same tank you are drawing from. We have 4 tanks so this option is pretty important. But, it seems to have worked well for a few decades on your vessel as is

Non standard plumbing. Are you sure about the routing? All would be well if there is a low mounted cross tie line, check for that.

My previous boat had a similar tank layout, and we could never leave both fuel valves open as even if the boat had only a slight list, the fuel would flow by gravity from the higher tank to the lower and increase the list.
Also, you should have the capability of returning fuel to the same tank that you are drawing from for both the main engine and the generator.

Install one of these, problem solved . . . . . all of them.

The FV-65038 has 3 positions, left, right and off.

The FV-65038-A has 4 positions, left, both, right and off.

With either configuration, the the supply and return are switched together. One valve, one handle. It couldn't be simpler.

@Rossland: You are very correct. Leaving an open crossfeed is a big nono, and has been pointed out as a contributing factor in several fatal accidents. Recreational craft designers tend to assume that the user won't understand this, so sufficient margins are built into the boat to prevent it from having serious consequences, but it's still a bad practice.

Greetings,
I was not aware of the potential problems. I stand corrected and thank you.

My fuel plumbing is the same as the OP diagram and I have a crossover line the is always open.

Have fuel returns to all four tanks. I use one tank at a time.

I have run single engine boats with two or more fuel tanks for years. Although not required I suggest you would be better off adding a valve that allowed you to return fuel from the same tank from which it was drawn.

I have always used a separate pump to drain one tank right before fueling so that I have one tank with old(good) fuel and one tank with the new fuel. If you must return the fuel only to the starboard tank you will contaminate both tanks if you take on bad fuel.

One approach with a single engine boat is to operate off the starboard tank one day and the port tank the next day. Thus equalizing out. This requires the ability to direct the fuel return.

When I bought my NP43 the manufacturer recommended that the fuel crossover line be left closed due to the potential for a progressive list. Actually not an issue on my boat as I have a fuel transfer pump and the impeller keeps the fuel from passing through.

For a boat with a single fuel return all the OP needs to do is run first on the starboard tank and then the port tank. The time on the port tank will be less than the starboard tank.

On some engines that have a high return the selector vave that also sets the return is the way to go.

No fuel filling unknown tanks overcapacity , and its much easier to handle the fuel heat that goes with the returned fuel.

Labeled valves are fine , but a drawing with the tanks valves etc is even easier to understand.

In the future YOU may not be moving those valves.

My boat is now setup where the engine and generator draw and return to the starboard tank. I fill only the port tank. Then I transfer fuel as needed with a pump through a Racor 1000 that is a satisfactory fuel polisher. This allows me to watch new fuel going through the bowl to check for water and other contaminants. The plumbing is also setup to be able to polish the Starboard tank. The process also helps to use the older fuel first.

Ted

Just curious...how often does one get "bad fuel" when boating in North America?

He's not boating in North America. His boat's 'down south".

FlyWright said:

He's not boating in North America. His boat's 'down south".

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South America? Australia?

I see lots of elaborate fuel containment/delivery/filtering/polishing systems and it makes me wonder...is it really that common to get bad fuel, and how often has it stopped anybodies engine?

Had my boat's builder install a polishing system despite his contrary recommendation. My boatyard also disdained the need. As a result of miscommunication, the boatyard bypassed the polishing system. Nevertheless, the remnant system is still useful for transferring fuel among several fuel tanks, and haven't yet experienced a need here for polishing. Do have on-engine filters and dual Rycors.

MurrayM said:

South America? Australia?

I see lots of elaborate fuel containment/delivery/filtering/polishing systems and it makes me wonder...is it really that common to get bad fuel, and how often has it stopped anybodies engine?

Click to expand...

I got a bad load of diesel in Mystic, CT (my home port) once. That was in the early 90s. It was bad enough to shut me down 2 times before I got it cleared out.
I found out months later that someone else in my marina also fueled up that same day and had the same issues. The "crud" looked like large coffee grounds. They were actually large enough to get stuck in the fittings of my copper fuel lines.

MurrayM said:

Just curious...how often does one get "bad fuel" when boating in North America?

Click to expand...

In the last 20 years of chartering, I've gotten bad fuel twice. That's just over 1%. One was the marina I use regularly in Hatteras, NC. They replaced the crud filled tanks the next winter. The other was a transit stop in Virginia. Both incidents dropped the boat to barely an idle, but in a safe area. Not fun changing a separator filter in a hot engine space in a rolling boat. My regular marina has never been a problem. For the trawler when long distance cruising, you never know where you may fuel and how clean the fuel may be. What I do may be excessive, but dirty fuel is a problem I can easily deal with.

Ted

Trawlers fuel rather infrequently. When not fueling at their home port, the selection of the fueling stop is carefully done - low price usually means high turnover.

If you are looking for bad fuel stories check with the cruising sailboaters. They fill up much more often then we do, and they usually don't have a choice on locations. Their bad fuel stories are many.

Should we switch to the other fuel tank yet?

I guess it only has to happen once for it to become a priority!

" Not fun changing a separator filter in a hot engine space in a rolling boat."

Never is , but there is no reason to locate the tank selection or the fuel filters inside the ER.

No fun changing filters in any rolling boat , but not worrying about being burned by the engine helps!

Bad fuel, not often in our area, but it does happen. I got some a bunch of years ago. Friends have had it happen. Both dirt and water. % wise I would venture it is not a common problem but it only takes once to make us leery.

I regularly drain a small quantity of fuel from the filter a short time after refueling. My tanks are bottom feeders so it does not take long for junk to show signs of contamination. I still get a small bit of dirt or water periodically.