OEM Quicksilver 59078 140°F Thermostat for MerCruiser 2.5L/3.0L & 165
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Description
Description
Quicksilver 59078 is a 140°F thermostat for selected older MerCruiser inline engines. Verify both cooling-system configuration and serial number when replacing the thermostat.
- MerCruiser 120/2.5L: serial 2324347 and newer with a cast-iron exhaust manifold.
- Selected MerCruiser 140/3.0L engines through serial 0L340999 that specify a 140°F thermostat.
- MerCruiser 165 inline six-cylinder: 1970–1981, serial 2770032–5813433.
The 165 application is the inline-six engine, not the later four-cylinder 165. Closed-cooling and later 3.0L configurations can require a different thermostat. Confirm part number 59078 in your engine's parts diagram before ordering.

