Many good ideas and guidance. On my 2GM20F, I wanted a temperature gauge and created a compact adapter from a brass 3/8 BSP plug
which I drilled and tapped for a 1/8 NPT temp sender. This was from Faria as Teleflex in this size are not prevalent. The gauge could be from various US makers using the standard resistive protocol, 240-33 Ohms, 240 is empty tank, zero pressure, minimum Temp. This is used for a variety of marine/industrial instruments like fuel
level, temperature, and oil
pressure so these meters are actually the same but for the scales installed.
of threading a 3/8 NPT into a Yanmar
3/8 BSP port may work
but ill-advised as BSP is slightly finer thread and thread profiles differ too. You may only catch 2 threads poorly and you need electrical
connection (to Gnd) while avoiding leakage. The Catalina
special thermo sender is good alternative. If the T-stat housing ports
are plumbed to a water heater
then a tee of some sort is needed but you want the sender bulb in the water flow. I'd put this in the heater
feed hose (plus added ground connection). The Yanmar thermo switch can stay put and I agree with others that another dry thermo switch clamped at the mixing elbow
is good for early detection of lost cooling
I wanted Fuel
, Temp, and Ammeter, but shied away from oil
pressure. It would be nice but there is some risk installing a sender due to the physical size and weight of these if not threaded directly into the engine
port. An adapter or Tee adds mass and length and this extends the moment arm on a shaking diesel
so this should best be of steel/iron and kept short. An option is to fit the sender on a high pressure hose assembly, mounted where convenient (with a grounding wire).
Note that VDO made senders/gauges for both Euro (10-180 Ohm) and the USA (240-33 Ohm) protocols but the default was Euro type. A DVM can guide you on a used sender but verifying a used meter type requires a resistor circuit unless a known sender is on hand. Or you pursue the long VDO P/N. With 180 Ohm resistor from Gnd to "S", a Euro meter should read right to full scale while a USA meter will read about 1/4 scale. If the latter then try a 33 Ohm resistor for full scale.
My friend's boat
has wacko oil pressure readings which must be attributed to a sender and meter of differing protocol. It is not just the resistance range but also an opposite resistance slope
This Veethree site shows a table with the scales and resistance of the senders Intnl vs. USA: