My Account
Shopping Cart

Quicksilver 59078Q3 Replacement 140°F Thermostat Kit for MerCruiser Inline 4 & 6-Cylinder Engines

Manufacturer

Quicksilver

<h3>Quicksilver: The Marine Enthusiast&apos;s Trusted OEM Brand</h3><p>For boaters who refuse to compromise on quality, <strong>Quicksilver</strong> has been the benchmark for marine parts, accessories, and engine care products since 1950. Based in Fond du Lac, Wisconsin, Quicksilver operates as the parts and accessories brand of Mercury Marine — and that heritage is central to everything it makes. As the only marine aftermarket brand manufactured and recommended by an original-equipment manufacturer, Quicksilver brings factory-level engineering directly to boat owners, professional technicians, and weekend warriors alike.</p><p>What sets Quicksilver apart from generic aftermarket suppliers is its direct lineage to the engineers who designed the engines in the first place. Every component is engineered, tested, and manufactured with the same exacting standards as the original equipment it replaces. The result is a product line that fits right the first time and delivers the reliability boaters depend on — whether they&apos;re navigating calm inland lakes or pushing through demanding saltwater conditions.</p><p>Quicksilver&apos;s catalog spans more than 40,000 parts across 12 product lines, covering outboard and sterndrive engines from Mercury, Mariner, Yamaha, Honda, Evinrude, Johnson, Suzuki, and more. Among the most critical components in that lineup are Quicksilver Fuel Pumps, which are built to deliver factory fit and consistent fuel delivery across a wide range of outboard applications. Reliable fuel delivery is the foundation of engine performance, and Quicksilver&apos;s fuel system components are engineered to handle the demanding conditions of marine use — including compatibility with current fuel formulations.</p><p>Beyond fuel systems, Quicksilver is a go-to source for Propeller Parts &amp; Accessories that help boaters maintain and optimize their propulsion systems. From hub kits that protect both prop and gearcase to installation hardware and prop tools, these components are designed to the same tolerances as the drives they support. Proper propeller maintenance is one of the most impactful things a boat owner can do for performance, efficiency, and engine longevity — and Quicksilver makes that job straightforward.</p><p>The brand&apos;s commitment extends across lubricants, impellers, thermostats, anodes, fuel filters, oil filters, maintenance kits, and complete service packages — all engineered for the marine environment and tested to meet or exceed the standards of major engine manufacturers. Whether you&apos;re performing routine seasonal maintenance or tackling a more involved repair, Quicksilver provides the parts that restore your engine to peak operating condition.</p><ul style="list-style:disc"><li>OEM-backed engineering from Mercury Marine</li><li>Compatible with Mercury, Yamaha, Honda, Evinrude, Johnson, Suzuki, and Mariner engines</li><li>Over 40,000 parts spanning 12 product lines</li><li>Formulated and tested for freshwater and saltwater environments</li><li>Trusted by DIY boaters and professional marine technicians since 1950</li></ul><p>When reliability on the water is non-negotiable, Quicksilver delivers the peace of mind that only a true OEM-backed brand can provide.</p>

Part Number

59078Q 3
09/12/2036 11:17 AM
Sale Price

$32.49

In Stock (10+)

delivery box

Usually delivered within 2 days

Authorize Seller Badge
No Hassle Returns

No Hassle Returns

Live-in-stock inventory

Live-in-stock inventory

Fitment guaranteed

Fitment guaranteed

Product Details

The Quicksilver 59078Q3 Replacement Thermostat Kit is an OEM-quality cooling system component designed for older MerCruiser inline 4-cylinder and 6-cylinder engines manufactured by General Motors. This kit provides a direct, reliable replacement for a worn or failed thermostat, helping maintain proper engine operating temperature and protecting your marine engine from overheating or running too cold.

As a Quicksilver product, the 59078Q3 is built to Mercury Marine's original equipment manufacturer specifications — ensuring a precise fit and dependable performance that aftermarket alternatives simply can't match.

Kit Contents & Specifications:

  • 140°F thermostat — opens at the correct temperature for optimal engine performance
  • Cork thermostat gasket included — complete 2-piece kit, no additional hardware needed
  • Designed for older MerCruiser GM inline 4- and 6-cylinder stern drive engines
  • Cross-references: 59078T3, 59078T4, Sierra 18-3650, Sierra 18-3550

Installation:

  • Serviceable with common hand tools
  • Refer to your engine's owner's manual or service manual for thermostat removal and installation procedures

Quicksilver is Mercury Marine's premier brand for original equipment replacement parts, oils, and accessories — trusted by marine technicians and boat owners for over 65 years. Choosing Quicksilver means choosing parts engineered and tested to the highest marine industry standards.

cheapest price out there cheap ship

So far so good...

So far so good.

as of the moment, the shopping process has been great

Easy to find my b part number and fast ordering.

Easy website to navigate

Loved being able to validate and pay via amazon!

Great Product, you canot find a better price!!!<br><br>K&N Air Intake for 2010 Camaro 6.2

Quick and easy

quick and easy with extremely fast delivery

Fast

Share icon
Return Policy
Returns are easy at Boatplicity

Not happy with a purchase? No problem. We've made returning items as easy as possible. And most purchases can be returned for free for 30 days. Learn more about our Returns Policy