MerCruiser 160°F Thermostat Kit 807252T5 | GM V6 & V8 Standard Cooling

160°F Thermostat Kit — Part 807252T5

This is the genuine OEM 160°F / 71°C thermostat kit for GM-built MerCruiser V6 and V8 engines with standard (raw water) cooling systems. The kit includes the thermostat element, O-rings, and multiple gaskets for a complete thermostat service — no separate gasket sourcing required.

Critical distinction: This is the standard cooling / raw water version rated at 160°F. If your engine is equipped with a closed cooling system (heat exchanger), it requires the higher-temperature MerCruiser Closed Cooling Thermostat Kit 807252T4 instead. Installing the wrong temperature thermostat causes improper engine operation and can affect longevity.

Thermostat Element Reference

• Kit part number: 807252T5
• Thermostat element in this kit: Mercury MerCruiser 160°F Thermostat 8M0109441 (supersedes 807252T2)
• Related kit references: 807252Q5, 807252T8
• Aftermarket: Sierra 18-3647

Compatible Applications

For standard (raw water) cooled engines only. Confirm by engine serial number, model, and cooling configuration. Engines with the same displacement may use a different thermostat kit depending on their cooling-system design.

• 4.3L / 262 CID V6 — Selected standard cooling sterndrive and inboard applications, 1987–2016
• 5.0L / 305 CID V8 — Selected standard cooling sterndrive and inboard applications, 1987–2016
• 5.7L / 350 CID V8 — Selected standard cooling sterndrive and inboard applications, 1987–2016
• 7.4L / 454 CID V8 — Selected standard cooling sterndrive and inboard applications, 1987–2016
• 8.2L / 502 CID V8 — Selected standard cooling sterndrive and inboard applications, 1987–2016

When This Part Needs Replacement

• Engine consistently runs too hot or too cold
• Warm-up time has become unusually long
• Engine temperature fluctuates abnormally during operation
• The thermostat is confirmed to be sticking open or closed
• The thermostat housing is opened during cooling-system service
• Existing O-rings or gaskets are leaking or deteriorated
• Corrosion or mineral deposits are found inside the thermostat housing

Related Parts

• Mercury MerCruiser 160°F Thermostat 8M0109441 — thermostat element used in this kit
• Mercury MerCruiser Thermostat 160°F 8M0076464 — 496 MAG / 8.1L Big Block applications
• MerCruiser Closed Cooling Thermostat Kit 807252T4 — 170–180°F version for heat exchanger / closed cooling engines

Installation Notes

• Allow the engine to cool completely before starting thermostat service
• Drain cooling water as required by the service procedure
• Clean all thermostat housing sealing surfaces thoroughly
• Inspect the housing for corrosion, pitting, or cracking
• Match the correct supplied gasket to your exact housing configuration — the kit includes multiple gaskets for different applications
• Confirm correct thermostat orientation before installing
• Follow the applicable MerCruiser service manual for torque specifications
• Run the engine after service and verify stable operating temperature before returning to use

Parts Desk Insights

Most common customer issue: Ordering this kit for a closed cooling engine, or selecting by displacement without checking the cooling system type. MerCruiser thermostat kits split into two temperature families — 160°F for standard (raw water) cooling and 170–180°F for closed cooling. Both use similar housing designs on GM V6/V8 engines, but the wrong thermostat will cause the engine to run outside its intended temperature range. If your engine has a heat exchanger, you need the 807252T4 closed cooling kit instead.

Best use case: Ideal for scheduled thermostat service on standard-cooled MerCruiser V6 and V8 sterndrive and inboard engines, or any time the thermostat housing is opened for cooling-system maintenance. The kit format covers the complete service — thermostat, O-rings, and all required gaskets — so no additional sealing components need to be sourced separately.