Thermostat (160°F/71°C) – Fits MerCruiser 3.0-7.4L V6/V8 (Replaces 8072522, 807252T2, 8M0109441)
Thermostat (160°F/71°C) – Fits MerCruiser 3.0-7.4L V6/V8 (Replaces 8072522, 807252T2, 8M0109441) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Free standard shipping on all orders under 1 KG
Thermostat (160°F/71°C) – Fits MerCruiser 3.0-7.4L V6/V8 (Replaces ...
Product Details
The Sierra 18-3649 marine thermostat is a direct-fit replacement for MerCruiser 3.0L to 7.4L GM engines from 1987 and newer. Designed for Alpha and Bravo sterndrive models with fresh water (closed cooling) systems, it maintains the correct operating temperature of 160°F (71°C) for optimal engine performance.
This part provides a direct interchange for Mercury/MerCruiser 8052732, 8072522, 807252T2, 8M0091470, 8M0109441; Sierra 18-3649; Crusader 97895; GLM 13100/13101; and Mallory 9-43002/9-43157.
- Installs internally within the engine's cooling system housing.
- Engineered specifically for fresh water (closed) cooling systems.
- Package includes one high-quality 160°F (71°C) thermostat.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Mercury/MerCruiser | 8052732, 8072522, 807252T2, 8M0091470, 8M0109441 |
| Sierra | 18-3649 |
| Crusader | 97895 |
| GLM | 13100, 13101 |
| Mallory | 9-43002, 9-43157 |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure accurate fitment.
This thermostat fits a wide range of MerCruiser GM-based V6 and V8 engines from 1987 onwards that require a 160°F thermostat for a fresh water cooling system.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| MerCruiser | 3.0L GM / 3.0L MPI EC | 1987 and newer | 8052732, 8072522, 807252T2, 8M0091470 | Requires 160° thermostat |
| MerCruiser | 4.3L GM 262 V6 / Carb / EFI / MPI / LH | 1987 and newer | 8052732, 8072522, 807252T2, 8M0091470 | Requires 160° thermostat |
| MerCruiser | 5.0L GM 305 V8 / Carb / EFI / MPI | 1987 and newer | 8052732, 8072522, 807252T2, 8M0091470 | Requires 160° thermostat |
| MerCruiser | 5.7L GM 350 V8 / Carb / EFI | 1987 and newer | 8052732, 8072522, 807252T2, 8M0091470 | Requires 160° thermostat |
| MerCruiser | MX 6.2L MPI / Horizon Bravo | 1987 and newer | 8052732, 8072522, 807252T2, 8M0091470 | Requires 160° thermostat |
| MerCruiser | 7.4L Bravo GM 454 V8 | 1987 and newer | 8052732, 8072522, 807252T2, 8M0091470 | Requires 160° thermostat |
Technical Specs
- Product Type
- Marine Engine Thermostat
- Installation
- Internal, Engine Cooling System
- Temperature Rating
- 160°F (71°C)
- Cooling System Type
- Fresh Water Cooling (Closed Cooling)
- Housing Material
- Metal (Stainless Steel)
- Dimensions
- Approximately 5 x 5 x 4 cm
- Weight
- 0.12 lb (0.05 kg)
- Warranty
- Limited Lifetime (Sierra products)
What’s in the Box
- 1 x Thermostat (Replaces 8M0109441)
Installation Notes
- Ensure the engine is cool and disconnect the battery.
- Drain the coolant from your fresh water cooling system into a clean container.
- Locate the thermostat housing on the engine and remove the bolts.
- Carefully remove the old thermostat and discard it.
- Clean both the housing and engine mounting surfaces, removing any old gasket material.
- Install the new thermostat, ensuring it is oriented correctly. A new gasket (sold separately) is required.
- Re-secure the thermostat housing and tighten bolts to the manufacturer's recommended torque.
- Refill the cooling system with the appropriate coolant.
- Reconnect the battery, start the engine, and check for leaks and proper operating temperature.
Troubleshooting & FAQ
How do I know if I need a 160°F or a different temperature thermostat?
Always consult your engine's service manual. This 160°F thermostat is specified for the listed GM-based MerCruiser models from 1987 onward using fresh water cooling. Using the wrong temperature can negatively affect performance and engine health.
What are the signs of a failing marine thermostat?
Common symptoms include engine overheating (stuck closed), running too cool (stuck open), erratic temperature gauge readings, and decreased fuel economy.
Can I use this thermostat in a raw water (open) cooling system?
No. This unit is specifically designed and calibrated for fresh water (closed) cooling systems. Using it in a raw water cooled engine will result in improper operating temperatures and potential engine damage.
Is a gasket included with this thermostat?
The package contains the thermostat only. The required thermostat housing gasket must be purchased separately to ensure a proper seal.
How often should a marine thermostat be replaced?
As a preventative maintenance item, it is wise to inspect the thermostat annually and consider replacement every 2-3 years, or as recommended in your engine's service schedule. This is especially important in saltwater environments.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or quality control.
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