SKU: 25835684760

Thermostat Kit – Fits Mercury/Mariner 70-125 HP 2-Stroke (Replaces 803061T1)

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Description

Thermostat Kit – Fits Mercury/Mariner 70-125 HP 2-Stroke (Replaces 803061T1)Thermostat Kit Fits Mercury Mariner 70 125 HP 2 Stroke (Replaces 803061T1) This thermostat kit is designed for Mercury Mariner 70 125 HP 2 stroke inline 3 & 4 cylinder outboards from 1987 and newer. It ensures your engine maintains the correct operating temperature for optimal performance and longevity. This kit serves as a direct replacement for several OEM and aftermarket part numbers, offering a reliable and cost effective solution for your cooling

Thermostat Kit – Fits Mercury/Mariner 70-125 HP 2-Stroke (Replaces 803061T1)

This thermostat kit is designed for Mercury/Mariner 70-125 HP 2-stroke inline 3 & 4 cylinder outboards from 1987 and newer. It ensures your engine maintains the correct operating temperature for optimal performance and longevity.

This kit serves as a direct replacement for several OEM and aftermarket part numbers, offering a reliable and cost-effective solution for your cooling system maintenance.

  • Includes all necessary gaskets and seals for a complete installation.
  • Engineered to meet or exceed OEM specifications for fit and function.
  • Rated to open at 122°F / 50°C to regulate engine temperature.

Part Number Cross-Reference

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

Brand Part Number
Mercury (OEM) 803061T1
Sierra 18-3569
Sierra 18-3549 / 18-0339
GLM 13124
Mallory 9-43155 / 9-43014 / 9-60004
GHmarine 18-3569

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.

80
Brand Model Rated HP Stroke Years OEM Part No. Notes
Mercury 70 70 2-Stroke 1987+ (A996142 & UP) 803061T1 3 Cylinder
Mercury 75 75 2-Stroke 1990+ (C222000 & UP) 803061T1 3 Cylinder
Mercury 802-Stroke 1987-1990 (A996142 & UP) 803061T1 3 Cylinder
Mercury 90 90 2-Stroke 1987-2007+ (A996142 & UP) 803061T1 3 Cylinder
Mercury 100 100 2-Stroke 1987+ (B209468 & UP) 803061T1 4 Cylinder
Mercury 115 115 2-Stroke 1987+ (C100000 & UP) 803061T1 4 Cylinder
Mercury 125 125 2-Stroke 1987+ (D283222 & UP) 803061T1 4 Cylinder

Technical Specifications

Specification Value
Product Type Thermostat Kit
Installation Direct OEM replacement
Temperature Rating 122°F / 50°C (Note: some sources may list 120°F)
Housing Material Brass/Copper (thermostat), Metal (housing components)
Housing Color Copper/Brass with Black/Gray Gaskets
Fitting Type Direct fit to thermostat housing
Operating Temperature 122°F / 50°C (opening temperature)
Warranty 1 Year (aftermarket versions)
Other Technical Attributes For cooling system maintenance

Package Contents

  • 1 x Thermostat (14586)
  • 1 x Thermostat Seal (62386001)
  • 1 x Thermostat Cover Gasket (430068)
  • 1 x Washer (47533)

Installation Guide

Refer to your engine’s service manual for detailed instructions. The general steps for replacement are as follows:

  1. Safety First: Disconnect the battery cables and ensure the engine is cool to the touch.
  2. Drain Coolant: Place a container under the engine and carefully drain the cooling system.
  3. Access Housing: Locate and remove the bolts securing the thermostat housing cover.
  4. Remove Old Parts: Take out the old thermostat, gasket, and seal. Note their orientation.
  5. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and cover, removing any old gasket material or corrosion.
  6. Install New Thermostat: Place the new thermostat into the housing, ensuring it is correctly oriented. Install the new gasket and seal.
  7. Reassemble: Re-install the housing cover and tighten the bolts to the manufacturer's specified torque.
  8. Refill System: Refill the cooling system with the recommended coolant.
  9. Check for Leaks: Reconnect the battery, start the engine, and let it reach operating temperature. Carefully check for any leaks around the housing.

Troubleshooting & FAQ

Q: How can I be sure this thermostat kit fits my specific Mercury outboard?
A: The best way is to match your engine's serial number to the ranges listed in the "Compatible Engine Models" table. You can find your serial number on the engine's transom bracket. Our Mercury Serial Number Guide can help you locate it.

Q: What are the signs of a faulty thermostat?
A: Common symptoms include the engine overheating at various speeds or, conversely, failing to reach its normal operating temperature. An inaccurate temperature gauge reading can also indicate a problem.

Q: What temperature does this thermostat operate at?
A: This thermostat is designed to open at 122°F (50°C). This allows the engine to warm up quickly and then regulates the temperature to prevent overheating.

Q: How often should I replace my outboard's thermostat?
A: It is recommended to replace the thermostat and gaskets as part of your regular cooling system service, typically every 1-2 years or 100-200 hours, especially if operating in saltwater. Always refer to your owner's manual for specific maintenance intervals.

Q: OEM vs. 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.
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 25835684760

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Martin V.
Birmingham, US
★★★★★ 5
Modern luxury with summer fabric that performs above its price!
Color: Beige, Size: 14, Color: Beige, Size: 14
Wow! My son wore it for Easter Sunday and this suit fits the bill! The linen material is spot on--not too heavy and not too light especially since the weather is warming up now. The jacket is quality made--the design is modern executive, the stitches are strong no flaws to note. The pants are tad bit longer but that's okay, build quality is also great. The white shirt is decent and matches well with the rest of the set. The bow tie and tie itself is a great complimentary to the set, though optional to wear. The whole set just has that quality you would really look for in the price range you would want to pay. Overall, best value for for the, wear right outside the bag, maybe a light ironing otherwise it's perfect! I highly recommend it, no complaints here very happy with this suit!
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Reviewed in the United States on April 5, 2026
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Ariel B.
Alexandria, US
★★★★★ 4
Heavy linen character, but a beautifully tailored suit!
Color: Beige, Size: 4, Color: Beige, Size: 4
This is a really nice linen suit! The jacket is beautifully made and well-tailored, with a fun speckled texture that has lots of pretty color variation (we ordered the beige). When I placed it side by side with a similar linen suit from another brand, the difference in the linen texture was really noticeable — this had a much stronger linen character that stands out! It has three useful pockets on the outside of the jacket, which is great for little hands. The only downside is that one of the inside pockets is just for show (faux), which was a bit surprising and somewhat disappointing for my little guy. The pants have pockets too, but they aren’t very deep — perfect for small treasures, but not much more. The pants are made from a lighter, thinner single-layer linen compared to the fully lined, double-layer jacket, which makes sense for comfort and easy movement. The pants didn’t come with a front crease ironed in, so you’ll want to press one yourself. The linen did pick up some creases from being folded in the package, but it doesn’t seem quite as wrinkly as some other linen fabrics I’ve tried. Still, like most linen clothes, especially for boys, the pants will need occasional ironing to keep them looking neat and crisp, especially after a day of play and general wear. The structured, lined jacket stays looking smoother and more put-together with less effort. It also came with a bow tie, a neck tie, and a tuxedo-style white shirt as extras. The ties aren’t great quality — they’d work fine for quick photos but probably won’t hold up to much actual wear. The formal white shirt feels a bit funny paired with the casual linen suit, but I don’t mind at all. We already have white shirts that we prefer, so we’ll use those instead. For us, the extras are really just bonus items we won’t plan on using. Overall, it’s a handsome little suit that’s perfect for special occasions like weddings, family photos, or holiday events. My kid looked adorable in it! The stronger linen texture on the jacket gives it a premium feel that I really like. Just be ready for a bit of extra care with the pants to keep everything sharp.
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Reviewed in the United States on April 8, 2026
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chzgr8er
Belleville, US
★★★★★ 5
Great suit set
Color: Light Grey, Size: 4
It is incredibly attractive and includes everything a young child needs for a special occasion. The material is a 75% polyester and 25% linen blend, and the outer fabric feels remarkably smooth. Its unstructured design allows for an attractive, natural drape, and the blend conveniently allows for machine washing at home. As is typical with linen-based materials, the fabric can be naturally stiff and prone to wrinkling, so I recommend ironing or steaming it before use. The lightweight feel makes it an excellent choice for the spring, summer, and fall months. Overall, this suit offers exceptional value for the price.
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Reviewed in the United States on April 12, 2026
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Fort Morgan, US
★★★★★ 5
Summer wedding kids suit
Color: Navy, Size: 10 Years, Color: Navy, Size: 10 Years
Bought this suit for my son in the 10 youth size and honestly was pleasantly surprised by the quality for the price. The navy color looks sharp and dressy without being too stiff or uncomfortable. The material has a little stretch, which helped it fit nicely and made it comfortable for him to move around in. The adjustable waist was a huge plus, especially for growing kids. It fit true to size overall, though the blazer sleeves were slightly long on my son. The pants had a nice slim look without being too tight. We paired it with white sneakers for a more modern look and it came out adorable. This would be perfect for weddings, graduations, concerts, communion, school events, or family photos. Overall, very happy with the purchase and would definitely buy again.
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Reviewed in the United States on May 18, 2026
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Kindle Customer
San Leandro, US
★★★★★ 5
Very Modern Handsome Suit
Color: Grey, Size: 7 Years, Color: Grey, Size: 7 Years
This is an incredibly sharp looking suit for the little guy. Great price and features, too. I made a mistake in sizing up instead of down and first one was too sloppy on him and would need alterations. He is thin and very thin in the waist. There is a lot of adjustment with buttons in waistband and coat hides the bunching. This shirt and coat will easily take a fuller body than slim I believe. He loves posing in it and feels very classy. Best purchase for a formal suit that will last longer than most kids clothes size wise. Felt bad about returning but careful folding and packing got it good as new.
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Reviewed in the United States on May 20, 2026

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