Johnson Service Bulletin SB-936 - Starter Drive Assemblies

January 14, 1963. Identifies the noninterchangeable starter drive assemblies used on 75 HP V4S and V4A engines and specifies starter drive nut tightening requirements.

Johnson Motors Service Bulletin letterhead
January 14, 1963
Bulletin No. SB-936 Electrical
SUBJECT: STARTER DRIVE ASSEMBLIES: Part #377304 for V4S Engines (Magneto ignition) Part #378228 for V4A Engines (Battery ignition)
A quick glance would indicate that Starter Drive assemblies #377304 and #378228 are identical, however, they are not. Each assembly has a different drive pinion which prevents interchangeable usage.
Figure 1: original comparison of starter drive assemblies 377304 and 378228
CORRECT USAGE:
Part #377304 was first used in 1958 on the 50 h.p. model V4S (magneto ignition) engines, and since then, it has been used only on the V4S series through the current V4S engine. The short tooth drive pinion used in this assembly is listed as service part #204376.
Part #378228 was first used in 1961 on the 75 h.p. model V4A (Alternator equipped) engine, and since then, it has been used only on the V4A series through the current V4A engine. The long tooth drive pinion used in this assem- bly is listed as service part #307784.
RESULT OF IMPROPER USAGE:
Since it is entirely possible to accidentally install either assembly on the wrong engine the following results can be expected from so doing.
The short tooth drive pinion of assembly 377304 will not engage the alternator flywheel ring gear. It will however, lift against the under- side of the flywheel with considerable pressure and could possibly cause internal engine damage.
FIGURE 1.
The long tooth drive pinion of assembly #378228 will engage the V4S flywheel ring gear but will not completely disengage once the engine starts. Naturally this would result in starter motor damage.
TORQUE SPECIFICATION FOR STARTER DRIVE NUT:
The torque specification currently recommended for the starter drive nut is 25 to 30 foot pounds. Also, since the starter drive nut is of the self locking variety it should always be replaced whenever the starter drive is disassembled. The locking device which is built into the nut, looses some of its holding characteristic once the nut is removed. Use of a new nut and the proper torque application will best insure the security of this assembly.
RC:eb NOTE: Post on your 75 h.p. index.
JOHNSON MOTORS Robert Compton Service Department