Mercury Mariner Outboard 40 HP 50 HP 55 HP 60 HP 2-Stroke Thermostat 110°C

Maintain the correct engine operating temperature with this premium-quality aftermarket thermostat for Mercury and Mariner 2-stroke outboards. Manufactured to OEM specifications, this thermostat is a direct replacement for the original Mercury component and helps ensure efficient engine cooling and reliable performance.

Fits Mercury & Mariner Outboards

2-Stroke Models

40 HP (3 Cylinder)

Serial Number 0P325500 & Up
Serial Number 0T980000 – 1B208418
Serial Number 0T980000 – 1B209735

40 Jet

Serial Number 0P325500 & Up
Serial Number 0T980000 & Up

50 HP (3 Cylinder)

Serial Number 0P325500 & Up
Serial Number 0T980000 & Up
Serial Number 1B000001 & Up

55 HP (3 Cylinder)

Serial Number 0P325500 & Up
Serial Number 0T980000 & Up

60 HP (3 Cylinder)

Serial Number 0P325500 & Up
Serial Number 0T980000 & Up

Thermostat Specification

Opening Temperature: 110°C

Replaces Mercury / Mariner Part Number

850055001

OEM part numbers are used for reference only.

Features

Premium marine-grade aftermarket thermostat
Direct replacement for Mercury / Mariner thermostat
Opening temperature: 110°C
Manufactured to OEM specifications
Maintains correct engine operating temperature
Helps prevent overheating and poor engine performance
Fully compatible and interchangeable with the original component
Suitable for freshwater and saltwater use

Why Replace Your Thermostat?

A faulty thermostat may cause:

Engine overheating
Engine running too cold
Poor fuel economy
Increased engine wear
Reduced performance

Replacing the thermostat at the recommended service interval helps maintain efficient cooling and prolong engine life.

Why Buy From SSI Marine?

Premium marine-grade aftermarket parts
Workshop-tested by SSI Marine
UK stock ready for immediate dispatch
Same working day dispatch before 1 PM (Monday–Friday)
Royal Mail Tracked 24 delivery
Technical support available
Collection available from our Leigh, Manchester workshop

Buyer Responsibility

Please check your engine model and serial number before ordering.

Although thermostats may appear identical, Mercury used different thermostats across various engine ranges.

If you are unsure, send us your engine serial number and we will be happy to confirm compatibility.

Mercury Mariner Outboard 40 HP 50 HP 55 HP 60 HP 2 Stroke Thermostat 110° Replaces 850055001