fuel tank size and sump

[garyd]

My 41C model 1986 can have either a 400 gal. Or 500 gal. fuel tank. My paperwork says 400 gal the top of the tank says 500 gallons. I measure the outside dimensions conservatively and I get 450 gal. If i add a little here and there dimensionally I get 488 gallons.

Does anyone know if there is a sump with these tanks or are they flat across the bottom?

I guess I could take the sender out. But I was hoping someone would know. The sender still shows over 1/4 tank with 360 gallons burned off. Don't know if the sender is accurate.

thanks have fun boating garyd

 

[MikeP]

THe oem Hatt paperwork/blueprints for your specific boat will state the nominal fuel capacity of the tank(s) installed. If you don't have those papers, they are a good thing to have. You can get them from Hatt if you give them your hull number and 75 bucks. It's well worth it.

Re senders - on our 53MY the senders will show empty but a dip stick inserted in a spare fitting port in the top of either tank will show more than half full! With the gauges showing nearly empty I've never gotten more than 340 gal (total) into the boat's tanks. SInce it holds 702 gal in the oem tanks, the senders are VERY conservative. Whether they are oem or shorter ones added later by a PO to intentionally be conservative, I don't know.

I had meant to conduct a test by switching both engs to run on one of the tanks and running until the engines quit from lack of fuel, then fill that tank and see how much fuel it actually took. But I never did that. Maybe I'll do it when I head back to NY in the spring. Both tanks are pretty low at the moment so it would be a good time to do so.

 

[yachtsmanbill]

Hey Gary...
The 58 may be different with integral centerline tanks but here goes: I had to drill and tap a 1/4 NPT plug to get a piece of copper tubing into the bottom to pull any water / debris out of the tank bottom. Ended up with 20 - 30 gallons of water !!
I am sure theyve never been addressed before. With a pc. of 1/4 copper tubing I could feel the "V" at the lowest corner of the tank, on the keel line, getting to ALL the crud. With 2 tanks, this was AFT on the fwd tank, and FWD on the aft tank. I recommend this with all the diesel boats as the pickup is not
low-low even for polishing. Get the crud out and then polish the rest. You can transfer into the other tank, estimating gallonage on pump time. Not exact, but close.
21 years is a long time to accumulate crud IMHO. Copper is inserted into aft tank here. Forward plug is obscured by vacuum cleaner hose. Notice clean fuel at pump discharge.
Have fun sucking LOL !! ws

 

[yachtsmanbill]

FWIW--- these tanks are about 450 gallons each. ws

 

[garyd]

Mikep got the paperwork it shows 400 gallons that is what came std on these model 41's that year. But the top of the tank is clearly marked 500 gal and that was an option that year. And when I measured I got 450 gal.

If there is a sump then I'd bet they are 500 gal.

 

[dastahl]

I have a 42LRC401. I found my 4 tanks (750g) all read empty when they too have at least a third left in them. So I never run the tanks down far enough cause I don't want to have the engines quit.

When I finally ran down the center line keel tank at the dock (345g) until the motor stopped up with crap, filling it required only around 250 gallons.

$600 later the fuel cleaning crew said all the tanks were terrible, but are now clean. I had no warning of this. I have racors and only need to change them once a season, may be twice. The problem is there is so much fuel and I burn so little (Ok I go slow) and I re-fill the tanks at half. Now I try to run the tanks down much farther, the side tanks first, then re-fill them from the center tanks. But last season I only ran the boat 115 hours so when I filled it in the fall it took 435 gallons.

One of my fellow LRC owners runs the tanks dry, uses a shop vac taped to a copper tube, then takes the gage fitting off and vacs out whatever crud and water is at the bottom of the tank.

David Stahl
Skooch
Wonton Creek MD (Frozen over as is the CD canal)

 

[(Nobody You Know)]

One of my fellow LRC owners runs the tanks dry, uses a shop vac taped to a copper tube, then takes the gage fitting off and vacs out whatever crud and water is at the bottom of the tank.

I don't know that I would do this. Especially when there are too many 12V pumps that can be riged minimizing spark (withstanding that diesel fuel is however much less volatile).

Unless you can get to each compartment which are separated by baffels, fuel polishing, by "professionals", will only clean the fuel and tank section which is accessable.

It is remarkable how much water can accumulate in a tank over time. On a previous (brand X) gas powered boat with twin aluminum 75 gal. tanks I was fortunate to be able to unscrew a plug at the tanks rear - which was the lowest point - and, with a manual hand pump, remove around 5-6 gallons of water out of each tank.

A white "hazzardous material" bucket will allow you easily see what you are getting out of your tanks, and to quit when you begin to consistently get clean fuel.

Have fun

 

[garyd]

Well I took off my sender and it is 28.5 inches long. The outside height dimension of the tank is 18.5 inches not including the top and bottom thickness. Therefore it has a sump. I checked the operation of the float level and it worked fine. Used a 2 3/8 socket, extension, breaker bar, and boarding ladder as extra leverage. Boarding ladder is single round pipe design.

It looks like the sump is about the same size as the water tank. And it holds 150 Gallons so 360 plus 150 = 510 gallons. at .62NMPG thats 316 NM total till bone dry. Figure never use more than 85% gives you 268 NM. Cruising range. By that time I'm ready to stop anyway. LOL

So I can only conclude that I have a 500 gallon tank.

I'm going to run it till I've used over 400 gallons and I will find out for sure.

The inside of the tank was spotless.