My boat came equipped with dummy lights for oil pressure and temp, but I'd like to have more info. The engine is a Volvo Penta MD22P.

A Volvo Penta dealer quoted $681 for:

THERMOMETER (2" gauge) OIL PRESSURE GAUGE (2" gauge) FRONT RING BRACE KIT GASKET OIL PRESSURE SENSOR TEMP SENSOR

Seems pretty steep. When I replaced my alternator I found Valeo Rhone OEM alternators for $120 that Volvo Penta charges over $600 for. My assumption is these sensors/gauges are industry-standard parts from companies like VDO that would be available for 1/3 the price if I knew what to buy. Does anyone have a better understanding of this?