Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 27Get this manual
Voltage Regulator Test LAMPS BURN OUT WHEN ENGINE IS REVVED UP
The voltage regulator is defectiveReplace voltage regulator
4Excessive electrical load (from too many accessories) will cause battery to run downIf visual inspection determines that battery connections and wiring is OK, perform the following alternator and rectifier test
LAMPS BURN DIM AT WIDE-OPEN-THROTTLE
Run engine at midrange (approximately 3000 RPM) with number 94 lamps connected to voltage regulator output leadsNote lamp brightnessDisconnect the leads at one terminal of regulatorConnect the leads together using screw and nutIsolate (tape) connectionRun engine at midrange (approximately 3000 RPM) and note lamp brightnessIf lamps are considerably brighter than with leads connected to regulator, the regulator is defectiveIf lamps are NOT considerably brighter, check the alternator (refer to "Alternator Test," following)aAlternatorRectifierBatter y
Battery Charging System
DESCRIPTION