Thermostat Kit (130°F/55°C) – Fits Force 70–150 HP (Replaces F664068)

$37.50 $60.00

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Thermostat Kit (130°F/55°C) – Fits Force 70–150 HP (Replaces F664068) is backordered and will ship as soon as it is back in stock.

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Product Details

This Thermostat Kit (130°F/55°C) is engineered for Force outboard engines manufactured between 1990 and 1999. It is designed for compatibility with a range of Force 70–150 HP two-stroke outboard models and also fits select Mercury SportJet jet drive powerheads. This aftermarket kit provides a reliable solution for maintaining optimal engine operating temperature.

It serves as a direct replacement for Force part number F664068 and Sierra part number 18-3527, ensuring a precise fit and straightforward installation.

Designed for direct replacement of the original thermostat.
Meets or exceeds original equipment manufacturer (OEM) specifications for performance and reliability.
Maintains a consistent engine operating temperature of 130°F (55°C).

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.

Brand	Part Number
Force	F664068
Sierra	18-3527

Engine & Model Compatibility

Confirm your engine model and year range in the tables below to ensure correct fitment.

For Force outboards, this kit fits various 70–150 HP models from the 1990s. Check your serial number for 75 HP and 90 HP models to verify compatibility.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Force	Various	70	2-Stroke	1991–1995	F664068
Force	Various	75	2-Stroke	1998–1999	F664068	Serial: 0E288000–0E344999, 0E345000–0E369299
Force	Multiple Models	85	2-Stroke	1989	F664068	Models: 85LD9A, 85LD9B, 856K9D, 858I9C, 858F9C, 858X9H
Force	Various	90	2-Stroke	1991–1999	F664068	Serial: 0E093700–0E369299, includes variants 90LD91D
Force	Various	120	2-Stroke	1990–1998	F664068	Serial: 0E093700–0E344999, includes 1996-1997 models
Force	Various	125	2-Stroke	1988–1989	F664068	Models: 1251A8C, 125LD9A, 1258V8C
Force	Various	150	2-Stroke	1989–1992	F664068	Serial: 0E000001–0E093699

For Mercury SportJet models, this thermostat is compatible with specific 90 HP powerheads from the 1990s. Ensure your serial number falls within the specified ranges.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	SportJet	90	2-Stroke	1990s	F664068	Powerhead (Non-Oil Injection): 0E033711–0E066619 Powerhead (Oil Injection): 0E066620–0E095087 Jet Drive: 0E021000–0E151579

Technical Specs

Product Type: Thermostat Kit
Installation: Direct Replacement
Temperature Rating: 55°C (130°F)
Operating Temperature: 55°C (130°F)
Other Technical Attributes: Meets OEM specifications, produced in ISO9002 certified factory (per JLM Marine)
Warranty: 30 days (Green Bay Propeller & Marine LLC)

What’s in the Box

1 x Thermostat (55°C / 130°F)

Installation Notes

Disconnect the negative battery cable before starting.
Allow the engine to cool completely.
Place a drain pan under the thermostat housing and drain the engine block coolant.
Loosen and remove the bolts securing the thermostat housing cover.
Carefully remove the old thermostat and gasket. Note the thermostat's orientation.
Thoroughly clean the mating surfaces of the housing and cover, removing any old gasket material or corrosion.
Place the new thermostat into the housing in the correct orientation.
Position the new gasket and re-install the housing cover, tightening 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 around the housing as the engine warms up.

Troubleshooting & FAQ

How do I know if this thermostat fits my engine?

The most reliable method is to check the compatibility tables on this page. Match your engine's brand, model, horsepower, and year. For some models, you must also verify your engine's serial number falls within the specified range.

What are the signs of a failing outboard thermostat?

A thermostat can fail "open" or "closed." If it's stuck open, your engine will run too cool, leading to poor fuel economy, carbon buildup, and incomplete combustion. If it's stuck closed, the engine will overheat, which can cause severe damage. An engine alarm or an abnormally high or low reading on the temperature gauge are key indicators.

Is this a 130°F or 55°C thermostat? They are the same?

Yes, 130 degrees Fahrenheit (°F) is the direct conversion of 55 degrees Celsius (°C). This thermostat is designed to open at this temperature to allow coolant to circulate and maintain proper engine operating temperature.

How often should I replace my outboard's thermostat?

Thermostats don't have a fixed replacement interval, but it is wise to inspect them as part of regular cooling system maintenance (e.g., every 2-3 years or 200-300 hours). They are often replaced proactively when servicing the water pump, as they are a critical and inexpensive component for engine health.

Can a bad thermostat cause a false overheat alarm?

Yes. If the thermostat fails to open, the engine will genuinely overheat, triggering an alarm. However, if the engine isn't actually overheating but the temperature sender or gauge is faulty, you might get a false alarm. Always diagnose the cooling system comprehensively.

What is the difference between an OEM and an aftermarket thermostat?

This listing is for an aftermarket replacement, not an original equipment manufacturer (OEM) part. It is built to OEM-level specifications with comparable materials for fit and function. Our parts are manufactured in an ISO 9002 certified facility and are batch-inspected to ensure quality and consistency.

How fast is shipping and what does it cost?

We ship worldwide quickly, with typical transit times of 5–15 days for most regions. Standard shipping is free. If available for your location, expedited shipping options and their costs will be presented at checkout.

What is the warranty and return policy on this part?

This product is covered by a 1-year warranty against manufacturing defects under normal operating conditions. If you encounter an issue, please contact our support team with your order details for assistance. Returns are accepted within our standard window for items that are unused and in their original condition. See our full 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 component, not an OEM part.
Professional installation is recommended for safety and optimal performance.

About Sea Sierra

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Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
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