Mercury Optimax Models 135, 150, Direct Fuel Injection., Page 102Get this manual
CHARGINGSTARTING SYSTEM
4Brush replacement is recommended if brushes are pitted, chipped or worn to less than 0.25 in(6.4 mm)If necessary, remove brushes as follows: aRemove hex nut and washers from POSITIVE (+) terminal and remove POSITIVE brushes and terminal as an assemblybRemove bolts securing NEGATIVE () brushes and brush holder to end cap
aBrush HolderPositive BrushesNegative BrushesPositive Terminal