Johnson Service Bulletin SB-968 - Shorted Ignition Systems

Issued August 15, 1963, this bulletin describes a factory correction for water spray entering the lower powerhead area of Johnson 10 HP QD-23 through QD-24B outboards. The eight-step procedure uses the original three illustrated views.

Johnson Motors gray Service Bulletin header
August 15, 1963
SUBJECT: SHORTED IGNITION SYSTEMS.
Engines affected: 10 H.P. - Models QD-23 thru 24B
Several reports of shorted ignition systems on the above 10 h.p. engines have been received from the field. The problem results from water spray being drawn into the area around the powerhead through air intake holes immediately under and behind the bottom spark plug.
This is identical to a problem which was also experienced with some 18 h.p. engines (Ref. SB-941) and can be relieved in much the same manner. Proceed as follows.
(1) Remove starter housing and carburetor.
(2) Cover intake manifold opening into crankcase with masking tape. THIS IS IMPORTANT.
(3) Use existing holes A and B (figure 1) as pilots and drill two 1" dia. holes in lower pan (figure 2).
Figure 1.
Figure 2.
Over
Figure 1, pilot holes A and B and masking tapeFigure 2, drilling one-inch holes in lower pan
Page 2 SB-#968
(4) Plug 4 holes identified as "C" (figure 3) in rear of lower cover with service Part No. 203290 BUMPER. Apply small amount of trim adhesive to underside of bumper head prior to installing bumpers in holes - to keep them secure.
(5) Plug single small hole immediately be- neath bottom spark plug - identified as "D" (figure 3) with caulking compound or some similar filler.
(6) Lay motor on floor (front down) and blow off chips with air nozzle - VERY IMPORTANT.
(7) Remove masking tape. Assemble carburetor and starter housing back on motor.
(8) Check synchronization of carburetor and magneto - since linkage was uncoupled in removing carburetor.
Sincerely,
JOHNSON MOTORS
Robert Compton Administrative Assistant
RC:eb
NOTE: Post on your QD-10 H.P. Index.
Figure 3, four bumper holes C and lower spark plug hole D

Service reference

The bulletin specifies four 203290 bumpers for the rear lower-cover openings, two 1-inch holes in the lower pan, and sealing the small hole below the bottom spark plug. It refers to SB-941, describing a similar problem on 18 HP engines.