This custom made temperature sender is used exclusively in Yanmar Diesel engines aboard boats built by Catalina Yachts that used American made panels and engine instruments. The standard Yanmar engine and panel uses a sender with nonstandard threads and an impedance matched to European instruments. In order to use American instruments aboard your Catalina, the engine distributors had to replace the standard temperature senders with this custom sender before the engine was shipped to Catalina Yachts.
These replacement senders are machined to fit Yanmar's metric threads and the impedance matches that of our #Z2650 temperature gauge shown below with a maximum reading of 240 degrees. Many original senders a green seal that surrounds the electrical connection on the sender (click on the thumbnail at left). Current senders have a black seal as shown at left. We have reports of many different shapes of senders that may have been installed during production. The shape is not critical, but the impedance and thread pitch are.
1) Unless they are intimately familiar with Yanmar engines installed on Catalinas, it is highly unlikely anyone will be aware of this custom part. Speak to any normal Yanmar parts source either at a boat yard or any of Yanmar's many distributors across the country and it is likely you will receive incorrect information due to the specialized nature of this information.
2) It is rumored that at some point (reportedly in 2000 and 2001 but the exact years are questionable) the employee responsible for preparing the engines before forwarding them on to Catalina Yachts ran out of these custom senders. The engines were shipped to Catalina with Yanmar's standard senders installed without anyone knowing it. This might explain why some owners report problems with their temperature gauges on Yanmar equipped boats.
3) If you are having issues with your temperature gauge and have ruled out the wiring and gauge itself, then the sender is suspect. Test the complete temperature gauge system using the Temperature Gauge Test Procedure below under "May we also suggest".
4) If you own a recent Catalina built in Florida, the engine panel may have been supplied by Yanmar. If the tachometer has the Yanmar logotype on the instrument then most of the instruments are based on the European system and use different parts than above.
5) Regardless if you are installing a water temperature sender or a water temperature switch, never use any type of Teflon tape or pipe joint compound on the threads. The sender or switch are modulating the connection of the instrument to the ground by way of the engine block. If you insulate the threads, they can't make the connection to ground and the instrument will not function properly.