I had a defective WEMA water tank sensor on my 2000 H340. I could not find a suitable replacement match on the WEMA web site so I contacted them at info@wemausa.com. It turns out that the Hunter factory installed water tank sensor on my boat (marked 01-00, W2-17-H336) is a now discontinued model and has been replaced with the WEMA S3 series. This is a 0 to 180 ohms sensor and is 17 inches long. Curiously, the unit on my boat is a European, screw-in sensor which is mounted in a standard five-hole American style adapter ring. The gauge-compatible replacement for my boat is the European sensor # S3-432.
I had to deal directly with customer service at WEMA via email and phone and they were very helpful. As it turns out, you cannot purchase the new S3 sensors from the web site. The online sensors look the same but the ohms are different. The ones on the website are 240 ohms at empty and 33 at full. The replacement sender I need is 0 at empty and 180 at full. If you order online, you will need the entire system (gauge + sender) to make sure the units are compatible. I had to order my new sensor by phone directly from WEMA. Their contact number is on their web site.
I ordered a new sensor and unscrewed the old one from the mounting ring. The Hunter factory sealed the threads with some unknown caulking so I used a hot air hair dryer to soften the caulking and the sender unscrewed without any problem. There are only two wires to reconnect.