MEMBRANE 91748M

Function and technical context

The 91748M membrane is an essential component of the fuel supply system in Mercury, Mariner, Mercruiser and Yamaha marine engines. This piece acts as a pressure regulating valve within the mechanical fuel pump, maintaining the flow of petrol at the optimal levels required by the carburetor. The diaphragm constantly flexes to balance fuel pressure and ensure consistent delivery to the engine. If it deteriorates or breaks, it causes fluctuations in fuel pressure that result in starting difficulties, misfires, and noticeable loss of power while cruising.

When to replace this part?

Typical failure symptoms include difficulty starting the engine, rough idling, unexpected blackouts while cruising, and petrol deposits in the crankcase. It is recommended that the diaphragm be inspected and replaced during each annual seasonal maintenance check, especially if the engine has been idle for several months or if signs of internal corrosion are observed in the fuel pump. Preventatively replacing this component before a heavy boating season prevents costly breakdowns in open water and ensures reliable operation of your boat.

Engine Compatibility Table

Equivalent manufacturer part numbers