Listing to port / More fuel on port

We've had this boat for 10 days and 3-ish running hours on the engines and about that on the genset. (Obviously a newbie!)

We've got twin Perkins 135s. We have an interconnecting fuel line with valves at each tank. Shouldn't these valves be open to equalize fuel consumption?

Posts on the MTOA chatgroup concerning another boat with twins appearing to use differing amounts of fuel suggest that the two fuel tanks are not really interconnected and thus don't share fuel side to side. Those posts suggest that the engine's return lines might be piped to one tank.

With most set ups you can set it up whichever way you want. A dedicated tank to each engine, both running off one tank, or leave everything open and both engines will run off both tanks. With the latter configuration there are variables which will result in fuel not being used equally across the tanks.

One thing to note is that the engines will not necessarily use exactly the same amount of fuel, even if sync'd.

Also remember that your genset is running from one tank so that will also draw that down.

Our boat have 5 tanks. The first time out I sucked all the fuel from one and overfilled a tank that I was returning to Had to get towed in . I changed filters before I realized what had happened . I finally noticed that fuel was coming out of the vent . It took me a while to figure out the system .

I think you need to trace all your fuel plumbing and make a diagram of it showing all the connections and valves. It's otherwise impossible to predict what will happen if you open or close any particular valve.

The key things you need to look for are:

1) Where does each engine (mains and gen) draw from?

2) Where does each engine return fuel?

3) Where exactly in the flow is each valve?

Then a few things are critical when operating;

1) Your fuel return can never be blocked. Depending on the engine, you can do significant damage to the engine's fuel system and dump a lot of fuel in your bilge.

2) If you draw fuel from one tank, then there needs to be a way for the return to get back to the same tank. Otherwise you will be transferring fuel while underway, and can find yourself pumping fuel out of one tank and overflowing/spilling out from the other.

After you have figured out how everything works and how each valve should be set, consider putting colored tape around the valve handles. I've got red tape on valves that should always be closed, green tape around valves that should always be open, and yellow tape on valves that are meant to be operated under normal conditions. That way if you ever find yourself reaching for a red or green valve, you will stop and ask yourself what exceptional condition has you doing that. I've got one of those engines that will fail spectacularly if the return is blocked, so I have gone one step further and removed the handles from those valves and zip tied them to the valve body. So you really have to make an effort to close one of them.

Pack Mule said:

Our boat have 5 tanks. The first time out I sucked all the fuel from one and overfilled a tank that I was returning to Had to get towed in . I changed filters before I realized what had happened . I finally noticed that fuel was coming out of the vent . It took me a while to figure out the system .

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That's a great example of why you need to know exactly how YOUR boat is plumbed. How someone elses boat works is completely irrelevant. BTW, I pulled the same stunt once by forgetting to re-open a balancing valve after fueling.

Such fun we're having learning this new/old boat! Turns out the water system currently has its valves set to pull water from starboard only, thus the list to port. I'll go grovelling in the ER to suss out that system some time before the list grows again!

I opened the transfer interconnection between the tanks but it's only 1/2" hose so there is apparently no rush to equalize. The boat has a whole array of valves and tubing distributing fuel to and from the two, P&S, Racors, to the P&S engines. All valves are open and all very neatly laid out and business-like. Even though the engines are counter-rotating, they're mostly symmetrical - the fuel pumps, distribution and lines are on the starboard side of both engines. Thus the starboard side is more perfectly hidden.

Listing to starboard due to unbalanced port/starboard fuel tanks. Good to have a pump to transfer fuel among tanks.

Good that you found the apparent cause of the list.... The fuel tanks are susceptible to the learning curve also.

The perkins engines pump around 8 GPH. My engine burns about 1. So, for each hour I run I return about 7 gallons to the tank being returned to.

So it is important for you to learn how the fuel plumbing is routed.

Most twin systems are installed with supply and returns with multiple supplies, returns and options. Make sure you know how your engine is plumbed.

cappy208 said:

So it is important for you to learn how the fuel plumbing is routed.

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Hell yeah!!

If you do open to equalize make sure you close them after. Fuel should be drawn and returned from the top of tank. Also after you know the plumbing make sure, double check the valves are set the way they should be. I have drawn from tank and return to another.

Look in the stern, you never know what you may find. I found nearly a ton, yes a ton, of lead weight in mine. The PO had added the ballast to even out the weight distribution from moving the fuel tanks forward so he could add another 300 gallons of water in the stern.

What B? At the end of the first two weeks we've had the boat, I've got a Volvo wagon full of junk (AKA good stuff - to some PO) off the boat. No lead, though.

Being a sedan, it has a huge lazarette which is a magnet for all sorts of stuff.

Balancing trim on our vessel is a normal activity. I use a level to facilitate my eye as water and fuel valves are opened or closed for the various tanks. As mentioned already, return to same fuel tank you are drawing from.

Our vessel has 6 tanks containing about 1300 gallons of liquid to manage, or about 8500 lbs. Each vessel is different on this issue, you'll figure out yours - my best check is the martini glass with horizontal lines. Of course after 3 or so I'm not level.

twistedtree said:

After you have figured out how everything works and how each valve should be set, consider putting colored tape around the valve handles. I've got red tape on valves that should always be closed, green tape around valves that should always be open, and yellow tape on valves that are meant to be operated under normal conditions. That way if you ever find yourself reaching for a red or green valve, you will stop and ask yourself what exceptional condition has you doing that.

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All of your post was great advice, but I found this suggestion particularly cool. Thanks.

For most folks it is easiest to have the fuel tank selector ALSO direct the return fuel to that tank.

Point the handle at the tank you want to work from, DONE,no thinking.

These do cost more than ball valves but do make life far simpler .Made in various sizes.

​

Groco 6‑Port Fuel Valve, 1/...
$143.83
Walmart



KISS

We list to starboard because the previous owner put all 12 house batteries on the starboard side. As you mentioned, we can equalize this somewhat with moving fuel and water around. As has been pointed out, get to know your systems and your returns!

FF said:

For most folks it is easiest to have the fuel tank selector ALSO direct the return fuel to that tank.

Point the handle at the tank you want to work from, DONE,no thinking.

These do cost more than ball valves but do make life far simpler .Made in various sizes.

​

Groco 6‑Port Fuel Valve, 1/...
$143.83
Walmart



KISS

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That is definitely simpler, and safer in that an operator can't accidentally shut down the fuel return. However, its simplicity reduces some options. While I know that many frown on the practice, taking fuel from one tank and returning to another is a quick and effective way of moving fuel while underway.

Two minor suggestions. The liquor locker should be full and capable of balancing the list. Second, I would keep the water tanks separated. If you contaminate one, you still have water, and if you crack a tank or break water line or a fitting, you may not lose all of your water.

"While I know that many frown on the practice, taking fuel from one tank and returning to another is a quick and effective way of moving fuel while underway."

Indeed , BUT it must be monitored very carefully as the return fuel could overfill the tank selected , and there goes your range.

FF said:

"While I know that many frown on the practice, taking fuel from one tank and returning to another is a quick and effective way of moving fuel while underway."

Indeed , BUT it must be monitored very carefully as the return fuel could overfill the tank selected , and there goes your range.

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Not to mention your insurance after your insurance pays the fine for the diesel spill.