Don’t take your temperature with one of these!
Are you familiar with an outboard engine’s thermostat? We weren’t, until the other day that is. Of course, I had heard that the engine had such a part but until our last bit of engine servicing where we became intimately familiar with its cooling system, I had no idea where the thermostat resided nor its purpose.
From what I have read, the thermostat’s job is to control the amount of cooling water which reaches the engine. When the engine is first started and is not yet up to its recommended operating temperature, the thermostat only lets a small amount of sea water flow through the engine block. As the engine increases in temperature, so does the amount of water that the thermostat allows to flow through it.
Problems can arise in this system when the thermostat gets all clogged up, either with minerals from the sea water or by bits of rubber broken off from the impeller (a different problem altogether!). Sometimes they get stuck in the open position while at other times, they get stuck closed. As you might imagine, neither scenario is good. You can see in the image below what an old Yamaha thermostat looks like when compared to a shiny new one.
We returned from California with shiny new thermostats for our Yamaha engines.
Remember where you are reading this (Zero To Cruising) and thus, don’t take it as gospel but I have read that if you’re in a pickle and you feel that your thermostat is causing you problems, the engine will still run with it removed. It may not run well, and it may burn more fuel than it should, but you should hopefully still be able to make it back to harbor so that you can find a replacement.
Today, we’ll be taking a crack at servicing our port side engine. We plan to change the impeller, lower unit oil, engine oil, spark plugs and give it an overall cleaning and lube job. Hopefully we don’t run into any unexpected surprises that turn this one day job into a multi-day exercise like the last time!