Thermostat Repair Service Kit – Fits Mercury Marine 4-Stroke 8-30 HP Carb/EFI Outboards (Replaces 855676002, 8M0119207, 8M0139434, 855676005)

Vendor: JLM Marine
Availability: In Stock
Product Type: Thermostat
$27.73
$27.73
Subtotal: $27.73

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photo of thermostat repair kit for mercury marine 4-stroke 8-30 hp outboard motors, copper thermostat with spring mechanism and black rubber seal, round black rubber gasket, part number 18-43175

Thermostat Repair Service Kit – Fits Mercury Marine 4-Stroke 8-30 HP Carb/EFI Outboards (Replaces 855676002, 8M0119207, 8M0139434, 855676005)

$27.73

Thermostat Repair Service Kit – Fits Mercury Marine 4-Stroke 8-30 HP Carb/EFI Outboards (Replaces 855676002, 8M0119207, 8M0139434, 855676005)

$27.73

Thermostat Repair Service Kit – Fits Mercury Marine 4-Stroke 8-30 HP Carb/EFI Outboards

This comprehensive thermostat repair kit is designed for Mercury Marine 4-stroke outboards from 8 to 30 HP, specifically those with 209cc 2- or 3-cylinder Carbureted and EFI engines. It ensures your engine maintains the correct operating temperature for optimal performance and longevity.

The kit is also compatible with select Tohatsu 4-stroke outboards that utilize a thermostat with the same temperature rating. It serves as a direct replacement for multiple OEM and aftermarket part numbers, simplifying maintenance and repairs.

  • Includes thermostat, cover gasket, and seals for a complete installation.
  • Engineered for a precise, direct replacement fit.
  • Maintains a consistent engine operating temperature of 60°C (140°F).

Part Number Cross-Reference

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

Brand Part Number
Mercury 855676002
Mercury 8M0119207
Mercury 8M0139434
Mercury 855676005
Tohatsu 3NV010300M
Tohatsu 3R3-01030-0
Tohatsu 3R3010300M
Sierra 18-43175
Mallory 9-43175

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.

Confirm your engine model/year in the table below.

Mercury Marine

Brand Model Rated HP Stroke OEM Part No. Notes
Mercury 4-Stroke 8 4-Stroke 855676002/8M0119207/8M0139434 209cc 2-cyl engines
Mercury 4-Stroke 9.9 4-Stroke 855676002/8M0119207/8M0139434 209cc 2-cyl engines
Mercury 4-Stroke 15 4-Stroke 855676002/8M0119207/8M0139434 209cc 2/3-cyl engines
Mercury 4-Stroke 20 4-Stroke 855676002/8M0119207/8M0139434 209cc 2/3-cyl engines
Mercury 4-Stroke 25 4-Stroke 855676002/8M0119207/8M0139434 209cc 2/3-cyl engines
Mercury 4-Stroke 30 4-Stroke 855676002/8M0119207/8M0139434 209cc 2/3-cyl engines

Tohatsu

Brand Stroke OEM Part No. Notes
Tohatsu 4-Stroke 3NV010300M, 3R3-01030-0, 3R3010300M Compatible models

Technical Specifications

Specification Value
Product Type Thermostat Repair Kit
Installation Direct replacement
Temperature Rating 60°C (140°F)
Operating Temperature 60°C (140°F)

Package Contents

  • 1 x Thermostat (855676002)
  • 1 x Thermostat Cover Gasket (27-853702005)
  • 1 x Thermostat Seals (Set)

Installation Guide

  1. Disconnect the negative battery cable for safety.
  2. Allow the engine to cool completely, then drain the engine coolant into a suitable container.
  3. Locate the thermostat housing on the engine block.
  4. Carefully remove the bolts securing the housing cover. Note their positions if they are different lengths.
  5. Remove the old thermostat, gasket, and any seals. Take note of the thermostat's orientation.
  6. Thoroughly clean the mating surfaces of the housing and its cover to remove any old gasket material or corrosion.
  7. Install the new thermostat from the kit, ensuring it is facing the correct direction.
  8. Place the new thermostat seals and cover gasket as required.
  9. Reinstall the housing cover and tighten the bolts evenly to the manufacturer's recommended torque specification.
  10. Refill the cooling system with the appropriate coolant.
  11. Reconnect the battery cable, start the engine, and carefully check for any leaks around the housing.
  12. Allow the engine to reach operating temperature to confirm the new thermostat is functioning correctly.

Troubleshooting & FAQ

How do I confirm this kit fits my engine? This kit is made for Mercury Marine 4-stroke 8-30 HP outboards with 209cc 2/3 cylinder Carb/EFI engines, plus compatible Tohatsu models. To ensure a perfect match, please compare your existing part number with those in our "Part Number Cross-Reference" table and check the "Compatible Engine Models" list.

What are the signs of a failing thermostat? Common indicators include the engine overheating or, conversely, not reaching its proper operating temperature. You may also notice erratic readings on the temperature gauge, poor fuel economy, or reduced engine performance.

What if compatibility information seems to conflict for my engine? We acknowledge that some sources may offer varied compatibility ranges. For example, part number 8M0139434 is sometimes listed for a narrow 9.9-20hp range, whereas our data supports broader 8-30hp use. For the most accurate fitment, always check the part number on your original thermostat and verify it against our cross-reference list.

OEM vs. Aftermarket? 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.

How fast do you ship and how much does it cost? 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.

What is your warranty and return policy? 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.

We can ship to virtually any address in the world with free shipping available for most regions.

For our typical US and Canadian customers , our shipping timeframes are as follows:

  • Amazon FBA: orders will be delivered within 1-5 business days after placing the order (during certain special periods such as major promotions, Christmas, etc., the delivery time of Amazon FBA may be affected).
  • US warehouse shipment: orders will be delivered within 5 days after placing the order.
  • China warehouse shipment: orders will be delivered about 12 days after placing the order.

When you place an order, we will estimate shipping and delivery dates for you based on the availability of your items and the shipping options you choose. Depending on the shipping provider you choose, shipping date estimates may appear on the shipping quotes page.

Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can be found on its detail page. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.

Founded in 2002, JLM Marine has established itself as a dedicated manufacturer of high-quality marine parts, based in China. Our commitment to excellence in manufacturing has earned us the trust of top marine brands globally.

As a direct supplier, we bypass intermediaries, which allows us to offer competitive prices without compromising on quality. This approach not only supports cost-efficiency but also ensures that our customers receive the best value directly from the source.

We are excited to expand our reach through retail channels, bringing our expertise and commitment to quality directly to boat owners and enthusiasts worldwide.

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