Need help with MAIN/AUX tanks

[Peter.D]

I have 2 gas tanks. The main is a 152 gal and the aux is a 50 or 49 gal not sure. My question is how do I isolate the tanks to run on their own? I have used the fuel switch MAIN/AUX and I have put around 400 gals into the main and the aux is always full while I never put any fuel into it? Is there a way to seperate the tanks? I look into the rigging area and the 2 tanks say on or off.
Thanks

 

[CKJR]

The sending unit for the tank is probably bad. when both fuel valves are switched to aux, both engines pull off the 50 gal auxilary, when both are on main, both pull from the 150 gal main. I like to fill my main tank up 150 gal) and run off this using my total fuel burn on the flowscan to confirm actual fuel remaining in tank. I do not trust fuel gauges!!

 

[BobP]

Seems like you are confused with how the two tanks are filled. Previous owner should have gone over with you.

Each tank inlet fills it's own tank, one tank doesn't fll into another tank. That's for filling.

The dash panel switch is to select what tank the single gauge reads from. Each tank has it's own fuel level sensor, but you have only one instruement to read it.

Now, on feeds to motors (outlets from tanks) =
Back at the stern there are two identical hand valves, each with three hoses going into it, find them.
One is for one motor, the other for the other motor.

So, for each motor, you can hand select which tank the feed is coming from, either the aux tank or main tank.
Its all up to you, nothing is automatic. You controil manually by the valves where each engine gets it's fuel. If you want to use both tanks, then you can periodically swap tanks so both tanks get used.

Apparently, you are only using one tank now.

 

[Peter.D]

Thanks

I thought if both tanks were "on" in the rigging area the gas would flow between both tanks ? Guess not.
I think the sender is definitely gone. I also use total gallons used too. I wonder hom many gallons does 1 bar on the gauge equal? HMM
Peter.

 

[Hookup1]

Fuel tanks

BobP gave you the best description of what you have.

"for each motor, you can hand select which tank the feed is coming from, either the aux tank or main tank."

Each engine has a hand valve that selects Main/Off/Aux tanks. They determine which tank you pull fuel from. Each tank is isolated from the other - no fuel ever flows between them.

My first question is which way are these valves set? The little tip points to the tank your using and the long arm away...

What do you mean the aux tank is alway full? Are you topping it off or just reading the gauge?

The fuel gauge has 8 bars on it. When you are low the last bar starts blinking. They are not very accurate - more of a guide then a rule. The sending units are problematic - I changed both of mine out (use the WEMA senders).

 

[Peter.D]

Well for one I bought the boat from a broker. Nice guy but, the "hands on" if you will were not included. The information I have is from having done my research on quality boats. I decided on grady because in Rhode Island/Block island sound, the weather changes on a dime. I am very happy with the boat. I have been through the Grady web site almost as much as my full time job.
Of course there are alot of areas I have questions on and this web site was my deciding factor of what boat to purchase!!! Rant, Rant, Rant.
Anyway. I never put any gas in the Aux tank However, I have cruised on it for a while and never ran out of gas!!!! It is a 50 gal but I am sure i have cruised longer than capacity of this tank??? The broker did mention there was a bladder hook up for offshore to increase the 202 gal.
Unfortunately, I bought the boat at the end of the season, I have not had the time for trial and error. So I thank everyone in advance for my inexperience. I do have the owners manual from the web site.,
Awesome boat.
Peter

 

[BobP]

No problem about the dealer, don't worry about it.

There are plenty of members here who know more about the models than the customer service guys do at Grady (I bet!). Ask anything you'd like.

Check those valves and confirm there are three hoses going to each one, and what all the markings or plate reads. The valve (if it has three hoses)really has two "on" positions, not one, since it's a selector valve, not an "on" (open) / "off"(closed) type valve.

One of the three hoses runs to the respective motor, the other two will run one each to each tank. You should be able to follow the hose to the motor or gas filter first / since it stays in the stern, the other two run into the gas tank compartment under the floor. What I described repeats itself for each motor.

Take a piece of paper out and draw a diagram as explained above. Draw each tank as seperate units, like each motor.

If you want to know if the gas tank sender is working for the tank you are not filling, mark the level before, then add gas, say 10 or 15 gals, the gauge will move, if it doesn't, likely the sender. There is another simple test to do once the sender is disconnected to verify it is the sendor, not another part of the circuit.

Remember how to use your single gas gauge correctly to ascertain the level in the respective tank of interest.

 

[Hookup1]

I went through the Grady manuals looking for a fuel system diagram. I couldn't find one. Only thing I saw was the fuel tank select valve. On my boat they are located in the rear of on the port side - open the bait station lid and lift out the tub. Should be a pair of them near the battery charger. The other Sailfish owners can confirm the exact location.

The short end of the arm points to the active tank. In this diagram the fuel is being pulled from the Aux tank. I put some red nail polish on the tip of the arm to make this obvious.

 

[Grog]

Not much more to add but if you never switched the fuel valves, they're both set to feed off the main tank. When you try the secondary tank, only do 1 motor. In case the gas is bad you don't want to strand yourself. Each tank has 1 fill line, 1 vent line, and 2 feed lines. There isn't a supply pump in the tank so there is no way for the fuel to get from one tank to the other. The switch only send the level pickup signal to the gauge (the level sensors are GROSELY inaccurate).