For your model year there are three things on the alarm circuit; low gear lube, low oil pressure and high coolant temperature. Note the alarm uses separate sensors than the engine gauges do. Go to Documents and find the Mercruiser engine manual for your engine and review the wiring diagram including choke.
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2