Originally Posted by HenryD
I am redesigning my helm station and need to replace the tachometers. The current tachs are over 3" and just too big. I can find 2 1/16" tachometers but they are designed for gasoline engines.
I would check with Lauderdale as was mentioned by other posters. Here is some reference info for you on your JH:
The tachometer on Yanmar 4JH3 series diesels utilize a magnetic pickup sender (MPU) which converts the rotary motion of the engine to an electrical signal by counting the number of teeth on the ring gear.
The ring gear has 116 teeth and the output voltage of the MPU is 1.0V or higher at 500RPM measured across a 20kOhm load.
If you want to go with NMEA2000 instrument integration, life just got easy. Maretron manufactures a model EMS100 interface that plugs directly into the factory engine wiring harness on Yanmar GM, YM, JH, LP and LY series engines. Couldn't be simpler.