Purchased boat last year, had a mechanical oil pressure gauge. Found original gauge behind panel, purchased sierra 18-5899 sending unit and the gauge pegs 80psi as soon as the key is turned on, engine not running. No change when started, still pegged at 80. Ran wire directly from sending unit to gauge and same thing pegged at 80psi. Gauge must be bad. Found a few that look the same/identical on fleabay, and my question is are all the marine gauges run on the same ohms and/or do the VDO use another ohm scale?
I don't want to buy another gauge and it not work with the 18-5899 sending unit.
If the VDOs use another scale I need to know the correct sending unit to use with the original gauge.
Any help appreciated!