Yamaha Outboard Engine Thermostats

Yamaha Outboard Thermostats

TL;DR: A Yamaha outboard thermostat helps keep the engine at the right operating temperature and protects it from overheating. It's typically located under the cylinder head cover, and if it’s malfunctioning, it’s best to replace it before problems get worse.

The thermostat plays a vital role in regulating engine temperature in Yamaha outboards. If you've ever found yourself asking where the thermostat is located, you're not alone. In most cases, it’s tucked away under the cylinder head cover or near the water jacket—placement varies depending on the engine model. I didn’t know where to look until I popped the engine cover and noticed a small housing near the top of the block. Turns out, it wasn’t hard to reach at all.

When a thermostat fails—either stuck open or closed—it can cause temperature swings or even full-on overheating. Left unchecked, that kind of issue can do real damage to your outboard. That’s why keeping an eye on it and replacing it when necessary is more than just good maintenance—it’s peace of mind out on the water.

Browse our complete selection of certified Yamaha outboard thermostats to find the one that matches your Yamaha outboard engine's exact specifications. Not sure where to begin? We can help you pinpoint the location and pick the right part so you're not stuck mid-repair or mid-season.

A malfunctioning thermostat can lead to overheating, potentially damaging your Yamaha outboard. Shop Yamaha Online Parts' complete selection of Yamaha outboard thermostats to find the one intended for your exact Yamaha outboard engine model.

Where is the thermostat located on a Yamaha outboard motor?

The thermostat location varies depending on the engine model, but it’s generally found near the top of the engine block. Look just under the cylinder head or around the exhaust manifold—usually behind a small bolted housing. You may need to remove a few bolts and a cover plate to get to it. If you’re unsure, refer to your Yamaha service manual for exact instructions.

How do I check the Yamaha outboard thermostat location?

Start by inspecting the upper rear part of your engine. Look for a small rectangular or rounded cover that’s bolted down—it’s often labeled or positioned near the water outlet. Once you remove the cover, the thermostat should be visible underneath. Some models make it easier than others, but most follow a similar layout.

What are signs of a faulty Yamaha thermostat?

Watch for symptoms like your engine running hotter than usual, temperature gauge spikes, unusual water discharge, or unstable idle. These can all be signs the thermostat is stuck in the wrong position. If it doesn’t regulate flow properly, it might be time to replace it.

When should I replace my Yamaha outboard thermostat?

It’s smart to check the thermostat at least once per season—especially during spring prep or after running in murky or salty water. If it looks corroded, blocked, or won’t open/close properly, don’t risk it. A fresh one is a small investment that can help prevent major engine repairs later on.

Maintaining your Yamaha outboard means keeping its cooling system in top shape. A working thermostat ensures your engine performs at its best and stays protected from heat-related damage. And with the right part in hand, swapping it out can be a straightforward fix—not a frustrating mystery.