1997 Johnson Evinrude "EU" 90 thru 115 90 CV Service Manual, P/N 507267, Page 243Get this manual
RectifierRegulator Tests Variable Load Tests To test the operation of the rectifierregulator, you must be able to run the engine continuously at approximately 4500 RPM, such as in test tank, on marine dynamometer, or on the boatThe test consists of monitoring the system's response to partially discharged batteryTwo methods for performing this test are described belowVariable Load High Rate Discharge Tester
INotel The requires battery voltage from the purple lead to operateBefore proceeding, verify battery voltage at terminal strip purple leads when key is ON
1Disconnect battery cables
2Connect 0-40 amp ammeter in series between the rectifierregulator red lead and the battery side of the starter solenoid
3Reconnect the engine's battery cables
4Following the manufacturer's directions, connect the variable load tester (carbon pile) across the battery terminalsStevens Model NoLB-85 and Snap-on Model NoMT540D are examples of testers availableExcessive battery discharge rates might overheat battery causing electrolyte gassingThis might create an explosive atmosphere