Johnson Service Bulletin SB-975 - Engines Jumping Out of Gear

August 23, 1963

Subject: a - ENGINES JUMPING OUT OF GEAR b - 20 AMP IGNITION KEY SWITCH FUSE BLOWING

On Engines: MODELS V4A (L)-14 THRU 15E

Midway through the 1963 model year, #309041 clamp was added to the crankcase oil drain hose on all 75 h.p. engines. (Ref. Service Bulletin #SB-937 dated 1/14/63).

We have recently received reports that the lip of #309041 clamp is fraying the wire loom which houses the electric shift leads (See Arrow, Figure 1). These reports further advise that #309041 clamp has, in some cases, worn through both wire loom covering and shift lead insulation. The result is a short (grounding of shift lead wire to #309041 clamp) which interrupts the electric shift coupling - allowing the engine to jump out of gear momentarily.

FIGURE 1

FIGURE 2

In view of this problem we suggest checking for #309041 clamp on each electric shift 75 H.P. engine that comes into the shop - especially those engines which the owners claim are jumping out of gear. If the engine includes this clamp - merely remove it and turn it around so that its hook faces toward the powerhead (See Arrow, Figure 2). So doing turns the hook away from the wire loom and eliminates the possibility of wire loom fraying from contact with the clamp's lip. After repositioning the clamp, carefully tape any frayed area on the shift lead with a good brand of electrical tape.

(over)

Page 2 SB-# 975

1963 electric shift 75 H.P. engines also have a 20 AMP fuse between the ammeter and ignition key switch. It's possible that this fuse may blow in event the electric shift lead shorts against #309041 clamp. Replacing this fuse will again render the ignition and shift circuits operative, but will not protect against repeat fuse failure. Therefore, blown ignition key fuses also indicate the possibility of a short between #309041 clamp and shift lead wire.

Summary:

The foregoing is a known source of trouble and should always be considered when diagnosing malfunction in the electric shift circuit. However, shift circuit malfunction can similarly occur as a result of wiring shorts in other areas, principally on engines that have had the electrical wiring "rerouted" by either an inexperienced mechanic or by the owner himself.

Check especially for electrical wiring rubbing against areas where sharp diecast flashing may exist. Also, check for wear between the wire loom and starter mounting bracket on engines equipped with a Delco Remy Starter Motor. These are just a few examples of where shorts may exist in the electric shift circuit if the wire loom has been "rerouted".

Sincerely,

Robert Compton Administrative Assistant

RC/bk NOTE: Post on your V-75 Index.