Mercury – Quicksilver Thermostat Retaining Sleeve | Cooling System Component | Brass | 47508T

Overview

If your MerCruiser runs hot or the thermostat doesn’t seem to sit right, this little piece could be the missing link. The Mercury Marine 47508T Quicksilver Brass Retaining Sleeve holds the thermostat firmly in place inside the housing, keeping the cooling system sealed and working smoothly. It’s made from solid marine brass and built to handle years of use, heat, and vibration. Designed for MerCruiser V6 and V8 engines with the older two-piece (#1 design) thermostat housing, it’s a simple part that helps keep your engine temperature steady and your boat running right.

Key Features

• Purpose: Keeps the thermostat properly seated and aligned inside the housing.
• Material: Machined from marine-grade brass that won’t rust or corrode.
• Fit: Designed for #1 two-piece thermostat housings on early MerCruiser V6 and V8 engines.
• Performance: Prevents thermostat movement, leaks, and uneven coolant flow.
• Durability: Handles constant heat, pressure, and vibration without wearing out.
• Compatibility: Works with MerCruiser sterndrive and inboard V6 and V8 engines.

Engine & Boat Compatibility

• MerCruiser V6 (early 2-piece thermostat housing)
• MerCruiser V8 (early 2-piece thermostat housing)
• Older high-horsepower MerCruiser inboard and sterndrive models

Performance & Real-World Benefits

The 47508T thermostat sleeve might be small, but it’s critical to how your cooling system works. It keeps the thermostat tight in its seat, which ensures coolant flows evenly through the system and keeps your engine at the right temperature. A loose or missing sleeve can cause leaks, uneven heating, or even overheating.

This brass sleeve won’t rust or deform, even after seasons of exposure to salt, water, and high heat. Once it’s installed, you can count on steady operation and a properly sealed thermostat every time you fire up the engine.

Why Choose Mercury OEM

The Quicksilver 47508T is made by Mercury, so it’s cut and machined to fit perfectly inside your MerCruiser’s thermostat housing. Aftermarket sleeves might look the same but often don’t fit tightly or use the same corrosion-resistant brass.

Mercury parts are tested in real marine conditions — heat, saltwater, vibration, the works — so you know they’ll hold up. It’s one of those small, affordable parts that can save you from a much bigger repair later.

FAQ

Q1: Which engines does this sleeve fit?
It’s made for MerCruiser V6 and V8 engines with the early two-piece (#1 design) thermostat housing.

Q2: What’s it made of?
It’s made from solid brass, so it won’t corrode or seize over time.

Q3: Why replace it?
Over time, sleeves can wear or go missing, causing thermostat misalignment or leaks. A new one keeps the cooling system sealed and efficient.

Q4: Can it handle saltwater use?
Yes — brass is ideal for saltwater and won’t corrode like cheaper materials.

Q5: Why OEM?
Mercury’s OEM parts fit exactly right and last longer. You’ll spend less time fixing problems and more time on the water.