Moeller reed switch fuel sender question

[SBH2OMan]

As part of the re-power with the Honda, we replaced the old "swing-arm" style sending unit with a Moeller "reed switch" unit. It is installed at the very aft end of the tank, a few inches forward of the transom (I assume this is where the old one was - there used to be a mechanical dial under the pie plate that gave us a "backup" fuel gauge, but it is now gone).

The problem I'm having is that I put 100 gallons into her for sea trialing the new prop, etc. After 5 hours (and I have to assume somewhere between 25 and 50 gallons burned) the needle on the fuel gauge has not moved a single hair. Not a millimeter. While at rest, she reads a tick above 3/4. While underway, however, she reads FULL.

Our old gauge did not vary so much between when underway and when at rest. Are there baffles in these tanks on the older (1993) 2320s? Is the tank a regular rectangle, or does it have a "V" in the bottom that matches the hull? Are these sending units calibrated to the tank?

My understanding is that these senders are a straight-down assembly with a float that rises up and down on the shaft (rather than a swing arm), and that the only adjustment is for the depth of the tank. In other words, if the gauge reads "1/2" it does not necessarily mean than 1/2 of the total tankage remains; it merely means that the float is 1/2 way up the stalk.

Is my understanding correct? Any other words of wisdom/experience?

Thanks,

Brent

 

[SBH2OMan]

I received a diagram for the tank from Parker this morning. Here it is if anyone finds it useful

 

[Brent]

thanks

 

[DaleH]

While at rest, she reads a tick above 3/4. While underway, however, she reads FULL.

And that or ANY other gauge that works will do likewise! ONLY read fuel gauges when you are at rest on the water. When on a trailer, your bow could very well be a tad higher.

And when up on plane at speed, you bow is much higher, so all the fuel runs towards the stern, where your sender is, so it gets a FALSE reading due to all the fuel being in the rear. Personally, I've always preferred tank designs where the pickup was in the stern, but the sender was towards the bow, i.e., your fuel reading would go 'down' when up on plane. This caused some concern, but I'd rather have more fuel really available for use - than less, haha!

IMHO builders stopped the senders up at the other end of the tank due to rigging costs ... easier to plumb the wires to one general area.

My understanding is that these senders are a straight-down assembly with a float that rises up and down on the shaft (rather than a swing arm), and that the only adjustment is for the depth of the tank. In other words, if the gauge reads "1/2" it does not necessarily mean than 1/2 of the total tankage remains; it merely means that the float is 1/2 way up the stalk.

Not necessarily. Most senders of that type are designed so they stop 1" above the bottom of the tank. This is for safety, i.e., to stop the sender from penetrating the tank and piercing it, if in big waves and the boat and tank move. If you knew the dimensions of your tank, could could calculate the volume of your tank with 1" of fuel in it. Fuel volume varies with ambient temperatures, but we don't need to worry about that detail. Aircraft do, however, since they undergo extreme temperature variances and that is why they calculate fuel by weight.

I'd opine, if your sender is exactly half-way up the staff ... you have about 1/2 of the fuel on board. Think about it, while the sender is mounted an inch higher than the bottom, so is the pickup (though usually just off the bottom ~1/2" or so) and there's really no way to completely fill a tank anyway ... so you're essentially reading correctly with a sender of this type.

FWIW, those by WEMA USA seem to be the best and have been installed by many here. I haven't been terribly impressed with most Moeller products, seem to be of average design and quality, but I hope it works out for you.

 

[SBH2OMan]

Thanks Dale,

According to the diagram I received from Parker (and I attached above), the tank is actually smaller at the bottom than the top, meaning that the "1/2 way point" in terms of gallonage is going to be closer to the top than the physical 1/2 way point. In other words, the bottom half of the tank holds significantly less fuel than the top half. I imagine that it is possible to calculate the volume of the tank at various fuel levels and then just have a chart handy that shows gallons remaining. Easier would be to drain the tank completely (somehow without running out of gas on the water) and then refill it, counting the gallons and looking at the gauge.

This all becomes less relevant once I get the fuel management hooked up (waiting on the e7 unit from Raymarine and setting up the NMEA/SeaTalkng network)

 

[Brent]

Anyone using an ultrasonic fuel sender?

http://www.ssitechnologies.com/fuel.htm

 

[DaleH]

In other words, the bottom half of the tank holds significantly less fuel than the top half. I imagine that it is possible to calculate the volume of the tank at various fuel levels and then just have a chart handy that shows gallons remaining.

Oh my, well that certainly complicates things! Calculations would be simple ... but you'd need the overall length of the tank first.

 

[DaleH]

Anyone using an ultrasonic fuel sender?

http://www.ssitechnologies.com/fuel.htm

Holy cow, is that cool or what! That looks to be just the ticket for the other Brent, as they could make it custom to read to his tank profile! Read this:

"The Fluid-Trac® 2-Wire fuel level sensor has a distance accuracy of +/- 0.125 inches. Every fuel level sensor is programmed with a strapping table to take into account the unique shape of the fuel tank. If the fuel tank is irregularly shaped with the mid point of the tank holding only 1/3 fuel capacity, the fuel level sensor will indicate 1/3 capacity not 1/2 capacity as a traditional float fuel sender may."

 

[SBH2OMan]

Yea, sounds pretty cool. Wonder how to convert the signal to an analog gauge (or to a NEMA2000 gauge). I also didn't see anything about it being rated for marine environments...

 

[Brent]

Warthog5 posted this sender earlier
http://www.hardin-marine.com/p-211-2-wi ... ender.aspx

 

[DaleH]

"The Fluid-Trac® 2-Wire fuel level sensor has a distance accuracy of +/- 0.125 inches. Every fuel level sensor is programmed with a strapping table to take into account the unique shape of the fuel tank. If the fuel tank is irregularly shaped with the mid point of the tank holding only 1/3 fuel capacity, the fuel level sensor will indicate 1/3 capacity not 1/2 capacity as a traditional float fuel sender may."[/quote]

FYI, Fluid Trac 2-wire units and replace any marine gauges, e.g., Teleflex, Faria, etc., that operates on 33 to 240 ohm resistance senders. They are marine rated (ABYC certified) and cost $95 from US Marine - see here: http://usmarineproducts.com/product_inf ... cts_id=298

One needs to complete the PDF Configuration Sheet attached, as attached below, to have it customized to your tank size and shape, then it will read accurately.

 

[SBH2OMan]

AWESOME INFO! I wish I knew this before spending $80 to have the Moeller installed in the tank... :-(

 

[no limit]

No one is missing anything on the Ultrasonic Sender. I spent half a day filling out the forms and talking back and forth and waited for the quote. This is what I got.
..................................
Thank you for your inquiry into SSI Technologies Inc and our product line. Unfortunately; based on the information you provided, we are unable to assist you with this request. This product has a minimum order requirement of 200 pcs per year. It is currently not stocked by any distribution partners and unavailable for purchase at this quantity level.

Again, I apologize that we are unable to assist you with this particular request. Please keep us in mind for any further pressure, digital gauge or ultrasonic applications that you may have.
.........................................

Maybe they should put on the website in big letters MINIMUM ORDER 200 PCS