Johnson Service Bulletin SB-943 - 1963 75 HP Wiring Diagram

Issued February 22, 1963, this bulletin documents the addition of a 20-amp fuse to the 1963 V4A and V4AL-15 alternator-equipped 75 HP engines. The fuse protects the wiring but, if blown, also disables the ignition and starter circuits.

Johnson Motors service bulletin letterhead
February 22, 1963
Bulletin No. SB-943 Electrical System
SUBJECT: 1963 75 H.P. WIRING DIAGRAM - MODELS V4A, V4AL-15
IMPORTANT (20 Amp Fuse Added)
A 20 amp fuse was recently incorporated in the wiring harness on 1963 model V4A, V4AL-15 engines. It is connected between the generator terminal on the ammeter and the battery terminal of the key switch. See wiring diagram (arrow) on back side of this bulletin.
The fuse has been added to protect the wiring from overloads, however, if it should blow, due to an overloaded or shorted circuit, all engine electrical circuits, including the ignition circuit, become inoperative until it is replaced.
Since information concerning the fuse and its location has not been included in all 1963 model V4A, V4AL-15 Owner's Manuals, we suggest you inform owners of its location, also that carrying a spare fuse would be advisable. Always check this fuse first if the ignition "on" indicator fails to light with the key in the "on" position or the starter does not operate.
The electrical systems on other 1963 models remain unchanged and 1962 wiring diagrams should be used for reference.
JOHNSON MOTORS
Robert Compton Service Department
RC:eb
NOTE: Post on your model V-75 (75 h.p.) index.
1963 75 HP electric shift wiring diagram for Johnson V4A and V4AL-15 models, showing the 20 amp fuse and all original wiring connections
Factory page 2 - wiring diagram rotated for reading

Electrical system reference

The added 20-amp fuse is located between the generator terminal on the ammeter and the battery terminal of the ignition key switch. If the ignition-on indicator does not illuminate or the starter fails to operate, the factory recommends checking this fuse first.

Other 1963 model electrical systems were unchanged; Johnson directed dealers to use the 1962 wiring diagrams for those models.