18-3569 Thermostat for Mercury Mariner 70HP 75HP 80HP 90HP 115HP 125HP | JLM Marine

18-3569 Thermostat for Mercury Mariner 70HP 75HP 80HP 90HP 115HP 125HP | JLM Marine

This high-quality aftermarket thermostat kit is engineered for Mercury Mariner 2-Stroke outboards ranging from 70HP to 125HP. It ensures precise temperature regulation to protect your engine from overheating and maintain optimal operating conditions on the water.

This kit directly replaces OEM part numbers 18-3569, 803061T1, and related components, providing a cost-effective solution without compromising performance or reliability.

• Complete thermostat repair kit with all necessary seals and gaskets
• Designed for 2-stroke Mercury Mariner outboards from 70HP to 125HP
• Includes thermostat, rubber seal ring, and washer for complete installation

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here's a guide to help you identify your engine's serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

This thermostat repair kit includes the following components:

• 1 × Thermostat
• 1 × Ring Rubber Seal
• 1 × Washer

Installation Guide

1. Disconnect the battery and allow the engine to cool completely before beginning work.
2. Locate the thermostat housing on your Mercury Mariner outboard, typically near the cylinder head. Consult your engine manual if needed.
3. Drain the cooling system to prevent coolant spillage during removal.
4. Remove the thermostat housing cover by loosening the retaining bolts or screws.
5. Extract the old thermostat along with the worn rubber seal and gasket.
6. Clean all mating surfaces thoroughly, removing old gasket material and debris to ensure a proper seal.
7. Install the new thermostat into the housing, ensuring it is oriented correctly (check for directional markings).
8. Place the new rubber seal ring and washer into position as specified in your engine manual.
9. Reinstall the thermostat housing cover and tighten bolts to the manufacturer's recommended torque specification.
10. Refill the cooling system with fresh coolant appropriate for marine applications.
11. Reconnect the battery and start the engine, allowing it to reach operating temperature while checking for leaks.
12. Monitor engine temperature during initial operation to confirm proper thermostat function.

Troubleshooting & FAQ

Q: How do I know if my thermostat needs replacement?
A: Common signs include engine overheating, running too cool (below normal operating temperature), coolant leaks around the thermostat housing, or inconsistent temperature gauge readings. If you notice any of these symptoms, inspect and replace the thermostat as needed.

Q: How do I confirm this thermostat kit fits my Mercury Mariner engine?
A: Verify that your engine is a 2-stroke Mercury Mariner model rated between 70HP and 125HP. Cross-reference the OEM part numbers (18-3569, 803061T1) with your engine's parts diagram or service manual to ensure compatibility.

Q: How often should I replace the thermostat?
A: Thermostats should be inspected annually and replaced every 2-3 years or according to your engine manufacturer's maintenance schedule. Replace immediately if you notice overheating, corrosion, or cooling system issues.

Q: What's the difference between this aftermarket kit and the OEM version?
A: This aftermarket kit is manufactured to OEM specifications using comparable-grade materials and provides the same functionality as the original Mercury part. The primary differences are the branding and the cost savings, making it an excellent value without sacrificing quality.

Q: Is this an OEM part or aftermarket?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.