Water Tank Gauge

2001 MS 390
Water gauge has crapped out. Tank 1 won't read at all. Tank 2 shows 1/4 full when tanks are actually 3/4 full. Not sure to check sending units (which appear to be glued in), or gauge unit?

Anyone with any wisdom on where to start?

My 43 Mainship has the same gauge manufacture. Mine turned out to be the sending unit. I believe your sending unit is threaded in. It should just unscrew.

Thanks for the reply. With the wiring on the sending unit it does not appear there is enough wire length to rotate to unscrew very far.

That's usually the case. Before you cut any wires, See if it is threaded by trying to turn it. You may be able to cut some wire ties and get a little slack. They put in the sending unit then pulled wires to the gauge, never thinking that someone would need to change it

This looks like yours. Liquid Sensors - Marine Diesel, Fuel, or Water Level Sensor

vacser said:

This looks like yours. Liquid Sensors - Marine Diesel, Fuel, or Water Level Sensor

Click to expand...

Thanks, missing a link in your post?

That's the way the link copied and pasted. It is highlighted, Just click it

Vulcanbike said:

2001 MS 390
Water gauge has crapped out. Tank 1 won't read at all. Tank 2 shows 1/4 full when tanks are actually 3/4 full. Not sure to check sending units (which appear to be glued in), or gauge unit?

Click to expand...

The link vacser sent is likely the correct replacement unit; if not, the S5U might be. I think the only real difference is in the threads. In any case, my receipt for a replacement unit says S3U.

The unit you have is a prior product (I can tell from the year of your boat; ours was 2002 with the same older style sensors), since replaced with the newer stainless screw-in/out unit.

The new units are easier to attach to the tank; IIRC with the new mounting adapter ... probably the FL-2WE/FBR Mounting Adapter (from my receipts)... there's a shaped backing plate you can fit inside the tank, and then screw a top fitting to... and then the S3/S3U sensor screws into that.

The WEMA/KUS folks have been very helpful with details on what products to use, what lengths, mounting adapters, etc.

That said, each sensor will likely also have an inline fuse, probably 1-amp IIRC, somewhere in your system... so before replacing the sensors, you might want to just check fuses first.

As to calibration... it is what it is. Use some Mark I* Standard Eye Ball on the tank at various fill levels, make comparisons to what the gauges say at those known levels, work from there.

-Chris