Mercury Optimax Models 135, 150, Direct Fuel Injection., Page 88Get this manual
CHARGINGSTARTING SYSTEM
Current Output
1With engine shut off, install ammeter (capable of reading 60+ amperes) in series between TERMINAL on alternator and POSITIVE (+) terminal of battery2Start engine and allow to warm upAdvance RPM to 20003Insert tool, previously fabricated for VOLTAGE OUTPUT, through end cover and ground TERMINAL F
aTerminalToolJumper Wire to Engine GroundTerminalAmmeter
4Normal output is 60 amperes 2000 RPMIf output is normal, replace regulatorIf output is low, disassembly of the alternator is necessary to inspect and test individual components