You can probably learn what type of senders you now have installed to mate with your old gauges by looking at this table on the Faria site: https://fariabeede.com/site_manuals/IS0085d.pdf
It shows the resistance range for the 3 American senders that are resistive (oil pressure, fuel
level and temperature). They are all the same R range, 33 to 240 Ohm.
The European senders use all different R range from one another as shown.
Checking the fuel
sender is easy and you can check oil
pressure at zero psi. The thermistor for temperature is a bit tougher but you can probably figure that out too. If the originals are Yanmar
gauges they might even have their own protocol. Be sure to break the sender circuit while measuring Ohms. I think most Yanmar senders on the engine use the BSP pipe threads and, not a match for NPT threads. Adapters can be had or made though.