Flapper Valve Noise

All 1994 (MD) and 1995 (HU)

The exhaust pipes used on 1994 (MD) and 1995 (HU) stern drives have .040 in. (1 mm) of material removed from their wall thickness. The flapper valve bushings can come loose from the exhaust pipe allowing the flapper valve pin to elongate the exhaust pipe pin holes "a".

Whenever troubleshooting an engine far a clicking or metallic sound coming from the rear of the engine, remove the upper exhaust pipe and hose. Inspect the flapper valve bushings, pin, and bushing holes. If worn, replace the original bushing "b" with bushing O P/N 3855517. This bushing is harder and has increased shoulder width to make up for the .040 in. (1 mm) of removed material.

If the exhaust pipe is damaged, replace it or relocate and drill two new 5/16 in. pin bushing holes. Use Tool Guide, P/N 885254. The tool permits relocation of these off center holes for proper operation of the flapper valve.

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