Mercury – Thermostat & Seal Kit | Cooling System | Factory Marine Finish | 99155T1

Overview

There’s a certain calm that settles in once your engine reaches that perfect running temperature—the moment everything evens out, smooths out, and feels right. Any boater who’s spent long days offshore or cruising a familiar stretch of river knows that feeling well. It’s the reassurance that your system is protected, that your engine is breathing easy, and that your boat is ready for whatever the day brings. That’s exactly the kind of quiet confidence you get from relying on a Mercury Marine part like the 99155T1 thermostat kit.

Key Features

• Maintains a precise one-hundred-sixty-degree Fahrenheit operating temperature
• Includes both the thermostat and the correct seal for secure installation
• Designed specifically for MerCruiser V6 and V8 closed-cooling systems
• Marine-grade construction ensures dependable temperature control
• Engineered for efficient coolant flow and long-term durability
• Direct-fit design allows smooth, trouble-free installation

Engine & Boat Compatibility

• Made for 1998 and newer MerCruiser V6 and V8 engines built on General Motors blocks
• Ideal for boats equipped with closed-cooling systems requiring a one-hundred-sixty-degree thermostat
• Common on cruisers, bowriders, sport boats, houseboats, and multi-purpose runabouts
• Suitable for recreational and commercial marine applications where steady engine temperature matters

Performance & Practical Benefits

A reliable thermostat makes a bigger difference than most boaters realize—until the moment one fails. With the Mercury Marine part 99155T1 installed, your engine reaches its ideal temperature quickly and stays there with remarkable consistency. You’ll notice the idle smooth out, the throttle respond more predictably, and the engine settle into a steady rhythm that just feels right.

Because it’s built specifically for marine use, this thermostat holds up under constant changes in load and water conditions. Whether you’re running at high rpm across open water or easing through a narrow channel, the temperature remains stable. That stability translates to cleaner combustion, better fuel efficiency, and less wear on critical components.

The included seal means the unit seats tightly without fuss. Installation feels straightforward—no strange gaps, no guessing about alignment. Just a secure, clean fit that you can trust. Once in place, it supports a cooling system that works as it should, offering peace of mind every time you twist the key.

Why Buy OEM

There’s a world of difference between a part that fits and a part that’s engineered for your exact engine. Mercury Marine parts are designed to meet precise temperature ratings and durability standards that aftermarket versions often miss. With the Mercury Marine part number 99155T1, you’re getting a thermostat built to match your cooling system’s exact needs.

It’s reliable, cost-effective in the long run, and ensures your engine performs the way it was designed to. When it comes to something as important as temperature control, choosing OEM isn’t just smart—it’s the kind of decision seasoned boaters make without hesitation.

FAQ

Q1: Which engines does the 99155T1 thermostat fit?

It fits 1998 and newer MerCruiser V6 and V8 marine engines equipped with closed-cooling systems requiring a one-hundred-sixty-degree thermostat.

Q2: What sets this apart from aftermarket thermostats?

It’s engineered to Mercury’s exact specifications, providing accurate temperature control and long-lasting performance.

Q3: How can I confirm it’s the right thermostat for my setup?

Check your owner’s manual or parts listing to verify the required part number for your cooling system.

Q4: Is it suitable for both freshwater and saltwater use?

Yes. It’s built for the full range of marine environments.

Q5: Is installation easy for most boat owners?

Many boaters install this themselves using common hand tools by following standard manual procedures.