Mystery fuel tank - 1973 43' DCMY

[Bill Root]

There is a 75 gallon fuel tank in the bottom of the bilge of my boat. It has a filler separate from the ones for the main tanks that is on the side deck. I originally thought it serviced the generator, but I have never been able to get it to take any fuel. Tracing the fuel lines indicates that it does not supply the generator. It's tied into the other fuel lines, but I can't see how any fuel would ever be drawn from it. The original drawings for the boat do not show this tank. Does anyone know what this tank does?

 

[TedZ]

How do you know it is 75 gallons? My 1972 43DC has a holding tank that is 135 gallons right between the two engines in the V of the keel. It could be used for fuel i'm sure but it would have to be transferred with a pump to the other two tanks to gravity feed.

Ted

 

[Will]

There are three center-line tanks with deck fittings in our 1980 43'. All are about 100 gals.
Engine room aft - Auxiliary fuel tank with suction and return lines to fuel manifold on aft ER bulkhead.
Engine room fwd through fwd BHD to area under galley deck is the Fresh water tank.
Area under galley deck to aft end of fwd cabin is the holding tank.
Will

 

[Bill Root]

It's definitely NOT the fresh water or waste holding tanks. I know where those are. I know it's a fuel tank because it has a fuel filler line going to a dedicated deck fitting marked "FUEL". I'm guessing it's 75 gallons by the size.

My boat was refit in 2003 by the PO. At that time the master stateroom was converted to a center queen with two new 200 gallon fuel tanks under the bed. The extra 75 gallon tank has fuel lines running from it to the fuel distribution manifiold on the aft engine room bulkhead. I can't tell where it goes from there, and as I said in the previous message, the tank would never take any fuel when I filled the others.

I'm stumped!

 

[sgharford]

I accidently discovered this on my '76 43 DC too. I opened the brass plug and expected spirits to fly out the way it sucked in air - probably never opened.

I called SAM's and think it was Mike Price who told me it was an extra 135 gallon tank built into the boat. Whoever it was believed it was to be used as future holding tank at time since they weren't requied back in the 'good ole days'.

 

[Jaxfishgyd]

I feel left out now. I can't see one, my blueprints don't show one nor is there a 3rd filler to indicate there is one.....

 

[Will]

Bill,
If the mystery tank has lines running to the fuel manifold and it has a fill pipe on deck, then it probably will not fill with fuel when you fill the after tanks. How is your fuel manifold designed? Our 43' has the OEM center queen bunk with a single tank under it. The Generator is plumbed directly to the aft tank and does not go through the fuel manifold. The fuel manifold has 4 valves, a suction valve and return valve for the PME and a suction valve and return valve for the SME. Each of those valves has three positions, Fwd Tank (the center line tank in the engine room), OFF and the aft tank (the main fuel tank under the queen bed). Is yours similar?

Otherwise, can you remove the face plate for your fuel manifold and follow the plumbing?

Will

 

[fissioneng]

The extra 75 gallon tank has fuel lines running from it to the fuel distribution manifiold on the aft engine room bulkhead. I can't tell where it goes from there, and as I said in the previous message, the tank would never take any fuel when I filled the others.

I'm stumped!

The engine fuel line goes into the manifold, so all you do is turn the valves for suction and return to activate that middle tank.

What do you mean by "never take any fuel"? Did it come up the fill hose or spurt out the vent when you tried to fill it? That could just mean it is full since it seems like you've never moved those manifold valves. You may have some messy fuel in there depending on how long it's been there.

Mine is 92 gallons and is plumbed exactly like Will describes.

 

[Finalee]

I have a similar arrangement. It is the aft belly tank and is plumbed to the genny.

 

[Bill Root]

Thanks for all the responses. here are some answers:

-I'll check the exact fuel line configuration when I'm at the boat tomorrow and post it.

- I know it won't take fuel because fuel squirts out the overflow when I try to fill it. It also sounds full when I wrap on it.

- This extra tank isn't in the original fuel flow diagram for the boat, so don't feel left out if you don;t have one.

- I had a complete fuel polish about 18 months ago. I wasn't on the boat when it was done, so can't be 100% certain the extra tank was cleaned.