1987 Johnson/Evinrude CU Outboards 35A thru 55 Service Manual, Page 109Get this manual
VRO Warning Signals Low Oil Signal complete procedure for testing the VRO "low oil" circuit can be found in VRO Installation Recommendations, this sectionNo Oil Signal 1Connect shop tank with 50:1 fueloil mixture to the fuel inlet fitting2Carefully disconnect the oil supply hose from the VRO oil inlet fitting 3Start the engine and run at 1000 RPM in gear4After the residual oil is exhausted from the VRO oil pump, the "no oil" circuit should activate the control box warning horn5The signal should be approximately 1 second on, 12 second off6If the horn does not sound within five minutes, check the Amphenol connectors and the tachometer circuit Check the boat's tachometer or temporarily attach known good tachometer to test the tachometer circuit7If the tachometer circuit and the warning horn circuit are okay, replace the VRO unit