GHmarine Mercruiser Thermostat Repair Kit 4.3-8.2L — 160°F Thermostat, Gaskets & Sleeve

The GHmarine 18-3647 Thermostat Repair Service Kit is a complete replacement set designed to restore proper engine cooling in Mercruiser 4.3–8.2L sterndrive models.

If your Mercruiser-powered boat is running hotter than normal or you’re rebuilding the cooling assembly, this repair kit supplies the thermostat and all the small parts needed to get the temperature control system back to specification. The kit matches OEM cross-references and fits a wide range of Mercruiser sterndrive engines, offering a 160°F temperature-rated thermostat, sealing components and a housing sleeve so you can replace worn pieces without sourcing multiple parts separately.

What components are included and why do they matter?

The kit bundles each part required to complete a standard thermostat replacement so you avoid leaks and misalignment after reassembly. Having the matching gaskets and sleeve improves sealing and ensures the thermostat seats properly for consistent cooling performance.

• One 160°F thermostat calibrated for Mercruiser engine cooling ranges
• One O-ring to prevent coolant seepage at the housing joint
• One housing sleeve to replace a corroded or deformed mating surface
• Four thermostat gaskets for reliable sealing and easy installation

Will this kit fit my Mercruiser model and replace OEM parts?

This repair kit is engineered to be compatible with many Mercruiser sterndrive engines between 4.3L and 8.2L, and it cross-references several OEM numbers so technicians can swap parts with confidence. Check your engine parts list or the OEM numbers to confirm a match before ordering.

• Compatible with Mercruiser 4.3–8.2L sterndrive models
• Replaces OEM part numbers such as 807252Q5, 807252T8, 8052732 and others
• Also cross-references GLM 13101, Mallory 9-43157, Sierra 18-3647
• Designed as a direct service kit for common Mercruiser thermostat assemblies

How should I use this kit during a repair or service?

Use the kit during a thermostat replacement, cooling system maintenance or when the housing shows corrosion. Remove the old thermostat and seals, inspect the housing bore, fit the new sleeve and gaskets, then install the thermostat to the specified orientation and torque for a leak-free assembly.

• Drain coolant and remove thermostat housing per factory procedure
• Replace old thermostat with the 160°F unit included in kit
• Install O-ring, sleeve and new gaskets to ensure proper sealing
• Refill coolant and pressure-test the system before returning to service

What performance and safety considerations should I keep in mind?

The thermostat’s 160°F rating is intended to maintain engine temperatures within the typical operating band for the covered Mercruiser engines. Always use recommended coolant and follow torque specs to prevent leaks; if the housing or surrounding components are heavily corroded, inspect and replace those parts to avoid premature failure.

• Thermostat opens and closes around the specified 160°F temperature
• Use compatible coolant and follow OEM maintenance intervals
• Replace damaged housing or hoses to ensure long-term reliability
• Verify seals and torque values during reassembly to prevent leaks

Who is this kit for: The GHmarine 18-3647 Thermostat Repair Service Kit is aimed at marine technicians, boat owners who do their own maintenance, and service shops working on Mercruiser sterndrive engines from 4.3L up to 8.2L. It’s useful for routine thermostat swaps, cooling-system overhauls, or when you need OEM-compatible replacements without sourcing multiple individual parts.