Help on Fuel Tank Configuation

[Alaskan Sea-Duction]

Fuel Tank configuration
Here is what my owner’s manual says:

A fuel manifold with selector valves is installed in the engine compartment on the bulk head. The manifold is connected to both fuel tanks (doesn’t mention the two aft tanks) and engines with supply and return lines, enabling either or both engines to be supplied from either fuel tank and return to either fuel tank.

Question: Leave aft tanks closed to use as back up OR leave open?

OK experts here is my tank configuration. I have 2 main 250 gallon tanks and 2 aux 50 gallon tanks with a fuel shutoff valve at the bottom of each tank.

The stbd tank feeds into a tee fitting. On the tee fitting one side goes to the fuel manifold and the other side to the Racor, then to the stbd engine. Return line to manifold.

The port tank comes into a tee fitting. One side goes to the rear 50 gallon tanks and the other goes to another tee fitting. Off this tee fitting one side goes to the Racor, the other to the fuel manifold. Return line to manifold.

Aft port tank goes to tee fitting. One side of tee fitting goes to port side main fuel line to main Racor.

Aft stbd tank goes to a tee fitting, one side to genny racor, the other side ties into tee fitting on aft port tank.

I also drew a schematic of the system in a MS word dock. Don't know how to post it, but will send it if you PM me your email address.

 

[Brooksie]

Fuel Tank configuration
I also drew a schematic of the system in a MS word dock. Don't know how to post it, but will send it if you PM me your email address.

We need that diagram. Try Microsoft Paint, you will have no trouble posting that just like a picture.

 

[Alaskan Sea-Duction]

We need that diagram. Try Microsoft Paint, you will have no trouble posting that just like a picture.

OK let's see if this works....

 

[Brooksie]

OK let's see if this works....

Worked fine. It looks like your genset has its own 100 gallon fuel supply (2X50) which can be redirected to your main engines as a reserve. That's good.

Depending how the manifold and its valves are configured (not shown), each engine could draw and return to its own tank or both engines could draw and return to one tank at a time. Which you do is a matter of preference.

Many prefer the later because it lessens the chances of getting contaminated fuel in both tanks but will imbalance your boat causing a list if the tanks are outboard (which they usually are). In that case they can be alternated runn on one tank for a set time and later the other for the same time.

Drawing and returning each engine to its own tank may be best and least complicated assuming clean fuel in your area.

Fuel must be drawn and returned to the same tank to avoid possible overflows.

 

[markpierce]

My boat has four fuel tanks with two manifolds: one for to engine and one for the returning fuel.

The arrangement is very flexible, and with the small pump on the polishing circuit, fuel can be transferred among tanks to maintain the boat's balance if necessary.

 

[Alaskan Sea-Duction]

All valves are marked as an "X" There are only 4 valves and each one of these are located at each tank.

Actually the genny has 600 gallons to draw from. Before I owned it the two back tanks were never used, so the genny was pulling fuel from the manifold/port main line. Return fuel from the engines and genny dump into the manifold. There are no seperate return lines going to the tanks, just the manifold.

As you can see the return lines are at the top. The two valves you see are for the sight gage.

Both big tanks feed from both sides, while the smaller tanks are combined at a tee and then joins the main port supply at the bottom right of the pic. ALL tanks feed into the manifold. I think the 2 smaller tanks were an option back in 1988, because the owner's manual only addresses the two main tanks.

So the question is do I run will all tanks open, or keep the 2 smaller tanks as a reserve?

 

[FlyWright]

Tom,

I'm a bit confused, so excuse me...but please verify the following 5 points:

1. Do the 50 gal tanks each run through the port Racor and then to the port engine or to bypassing the Racor to the manifold and then the gen?

2. It appears from the arrowheads that the manifold only feeds the gen, but accepts the return from the engines. To where does this return flow?

3. All fuel which flows from the 250 gal tanks flows either:
a. through the manifold to the gen
or
b. through its respective Racor to the engine.

4. No Racor filtered fuel passes to the gen and no manifold fuel passes to the engines.

5. All fuel which passes through the manifold goes only to the genset.

 

[markpierce]

So the question is do I run will all tanks open, or keep the 2 smaller tanks as a reserve?

No, I would draw from one tank at a time and rotate tanks so fuel is eventually drawn from all tanks to avoid stale fuel. Whatever tank(s) isn't(aren't) used at the present, is(are) the reserve tank(s).

 

[Bay Pelican]

Two questions:

How fast (days, weeks) do you go through 100 gallons of fuel? This is a factor in terms of advising you to use one tank at a time, or two at a time. Never four.

Do you have fuel transfer pumps so that you can refill one tank from another? Thus can you use a day tank of safe fuel after you have refilled and are still determining whether the new fuel is clean.

The ideal situation is to be able to draw from and return to any tank and to have all fuel go through a Racor before it goes to an engine.

Marty

 

[Alaskan Sea-Duction]

Tom,

I'm a bit confused, so excuse me...but please verify the following 5 points:

1. Do the 50 gal tanks each run through the port Racor and then to the port engine or to bypassing the Racor to the manifold and then the gen?

2. It appears from the arrowheads that the manifold only feeds the gen, but accepts the return from the engines. To where does this return flow?

3. All fuel which flows from the 250 gal tanks flows either:
a. through the manifold to the gen
or
b. through its respective Racor to the engine.

4. No Racor filtered fuel passes to the gen and no manifold fuel passes to the engines.

5. All fuel which passes through the manifold goes only to the genset.

1. The 50 gallon tanks are tied together, with a tee to the genny racor. When the smaller tanks are "off" (as has been the last 26 years) the genny gets its fuel from the port side of the manifold.

2. Return from all systems are at the manifold. If you look at the pic, both engine returns are on top of the manifold. The genny comes in on a tee on the stbd side.

3. All fuel from the two 250 gallon tanks flow to the manifold and respective racor. As stated above if the two smaller tanks are closed, the genny gets it fuel from the port side main line. But re-read the owner manual as BOTH tanks feed BOTH engines.

4. Yep it does. Genny has its own racor. At the bottom of the manifold it flow back to the main line and the respective racor.

5. Nope. All fuel that flows from return of the engines and genny are returned to the main line on both port and stbd side. Remember BOTH engines can be fed by both tanks or if you turn off a tank, then it feeds from the tank that is open.

 

[Alaskan Sea-Duction]

Two questions:

How fast (days, weeks) do you go through 100 gallons of fuel? This is a factor in terms of advising you to use one tank at a time, or two at a time. Never four.

Do you have fuel transfer pumps so that you can refill one tank from another? Thus can you use a day tank of safe fuel after you have refilled and are still determining whether the new fuel is clean.

The ideal situation is to be able to draw from and return to any tank and to have all fuel go through a Racor before it goes to an engine.

Marty

I would agree, but I am getting ready to make a trip up the west coast, so once I am settled at home, I can draw from the smaller tanks. I do not have transfer pumps. It would appear if the two main tanks are open, BOTH engines feed on both tanks, drawing down the tanks evenly.

It would appear I may have a simple, ideal system....

 

[FlyWright]

I had not seen post #6 when I posted my previous questions. That description and photo helps.

I guess I misunderstand the arrowheads as indicating direction of fuel flow. They make it appear the only fuel leaving the manifold is return fuel which flows to the genset.

 

[Alaskan Sea-Duction]

Sorry about the arrows, my piss poor drawing skills