Accessing Fuel Tank on Hunter 310 to Change Sending Unit

[viamalu]

I'm new to this forum and could use some help/tips on how to access the fuel tank sending unit on my 1998 Hunter 310. The fuel gauge started to fail intermittently last year. Now it simply doesn't work. There appears to be power to the fuel gauge as the dial does light up and shows "empty" even though there's plenty of fuel in the tank. This leads me to believe that the sending unit in the fuel tank needs replacement.

I haven't started yet, but in the aft port locker underneath the house batteries (and right above were the fuel tank is), there is a cut-out with a cover. It looks like a rough cut, not something you'd expect from the manufacturer-- but I could be wrong.

Is this a standard access point for the sending unit on 310s? (I want to make sure I'm in the right place before I start removing the batteries.

Also, what is the right replacement part? I've seen sending units by Moeller and Wema Systems. I realize I'll be bound by the bolt configuration of the existing unit. Did Hunter use different types of tanks/sending units on the 1998 310s?

Could it be a bad fuel gauge instead, notwithstanding that the gauge does light up?

Any help is appreciated before I start the project.
Dave.

 

[Ralph Johnstone]

Could it be a bad fuel gauge instead, notwithstanding that the gauge does light up?

I can only speak from a 1999 H310, but for openers, our fuel tank is port side and the batteries are starboard side.

Just over the fuel tank (in the lazzerette) is a very neatly covered cut out (factory) for access to the fuel tank.

Check your gauge to see if it's a WEMA. If so, remove the transmitter which is bolted to the top of the tank and see if the float is stuck. I had the same problem with the holding tank transmitter sticking and gave up on it after the first year. If it's free, on to a new gauge.

When you re-install the transmitter, be sure to seal it only with Permatex #2 sealant as it's the only thing I've found that will stick to the polyethylene tank.

 

[Miro Marinkov]

I picked up a 1998 H310 last year and my fuel tank is port side and the batteries are starboard side as well.

Also, holding tank may be polyethylene, but pretty sure the fuel tank is stainless.

The attached extract from the 310 Owners Manual may help.

From memory my sending unit is on top of the tank and accessible once you remove that factory cut out cover.

 

[viamalu]

Ralph and Wolf: Thanks for your comments! They are very helpful. I do have the engine battery in the starboard side lazzerette. The owner before me was an electrical engineer and he added a second bank of two 6V batteries for house power with a switch to use either bank to run the 12V electronics. Those are in the port lazerette just above (what I now know to be) the fuel tank cut out. While the cut-out looked a little rough, I wanted to be sure I was in the right place before I started the disassembly process. I'll re-post with some pictures as I do the project for the benefit of anyone else who may have to do this same project. Dave

 

[sbkidd001]

Thank you all. So helpful. I also have a 1999 H310 (as of this spring) but my batteries are on the port side, so now I know I will need to remove them to access the fuel tank.
I think my gauge is fine because the needle reads empty when the power is off but always only full when on. I plan to buy a replacement vertical sending unit, rather than the one with the swinging arm unless any of you has any concerns about that.
Question: how deep is the fuel tank? The sender should be ½" shorter. (I'm hoping to not have to remove the batteries twice, once to remove the old sender and measure the depth, and once to install the new one.) Thanks!

 

[Ralph Johnstone]

We have the same year and length boats.

You should be able to access the sender unit without moving the batteries too much. That's the theory but you know how well that goes in practice. Sorry I don't have a length for you right now but if I can remember, I'll pick up a measurement next time I am up at the boat.

The WEMA vertical sender is your best bet as mine has done very well for 21 years. HOWEVER, I would suggest a very careful check of your wiring to ensure there isn't a fault somewhere. These things are dead simple and don't usually fail unless the float becomes stuck. They don't usually stick in the fuel tank as the diesel is act as a lubricant. The holding tank ................... they're never free.

 

[sbkidd001]

We have the same year and length boats.

You should be able to access the sender unit without moving the batteries too much. That's the theory but you know how well that goes in practice. Sorry I don't have a length for you right now but if I can remember, I'll pick up a measurement next time I am up at the boat.

The WEMA vertical sender is your best bet as mine has done very well for 21 years. HOWEVER, I would suggest a very careful check of your wiring to ensure there isn't a fault somewhere. These things are dead simple and don't usually fail unless the float becomes stuck. They don't usually stick in the fuel tank as the diesel is act as a lubricant. The holding tank ................... they're never free.

Thank you very much Ralph! I'm just back from a sail and can see what appears to be a trap door right under the two house batteries. Sorry I don't have time to take them out right now but am now looking forward to the task!

 

[jssailem]

When I replaced the 1974 lever wire sender in my tank with a WEMA vertical sender, it was not out of failure but improvement in design and function. I stuck a stick down inside the tank to get a rough gauge of how deep the tank was at the location of the sender fitting. I then measured the distance with a tape measure. Easy task. The tank was 11.75 inches at that location. Assuming that the tank was full at that point and wanting to leave a bit of margin (think safety extra fuel) at the bottom of the tank I ordered a 10.5" sensor from WEMA. When the tank gauge says EMPTY... I have 1.25" of fuel in the tank.

Knowing that the tank carries 75 gallons and that equals 11.75 inches when full, I would have a reserve of approximately 7.9 gallons sloshing about at the bottom of the tank. Enough of a reserve to get me about 60nm. Granted that means the fuel at the bottom of the tank is not contaminated and the that my engine and the fuel system can suck up ever precious last drop of fuel. Ok say 50 nm with the Low Fuel warning light blaring. That is still a nice card to be holding should my foolishness let me draw down the fuel till the gauge says EMPTY.

Do not worry a lot about the "EXACT" depth of your tank. Do a "good" measure of the depth at the point you plan to locate the new sender. Adjust the length measured to not reach the tank bottom, and install a reliable sensor that provides a bit of "fuel reserve". You will know the value. (Enter it into your Boat Log so you can look it up in the future)

Then go out and enjoy your new found freedom.
Sail on....