Overheat warning

[HugoBoater]

Just bought a second-hand boat and used it for the 3rd time.

It got a 40HP Yamaha 2 stroke engine from 2013.

I anchored it for a few hours and when I started it to head home the overheat indicator started flashing. I was running it at low speed for a while and turned it off and on again but the indicator was still flashing.

I got towed back home since I did not want to risk anything.

When coming home I noticed that it's enough to turn on the ignition for the overheat warning to come on. Started it quickly to run it through with fresh water and the indicator kept flashing.


Since the warning comes on as soon as I turn on the ignition I suspect that it's a false indication. Cause even with some problems it would not overheat within a few seconds?

The water seems to be flowing as it should and it's not overly hot when coming out. As I understand it as long as the water flow keeps going I got water in the system? Correct?


Happy for any kind of inpuit.

[boscoe99]

Need the complete engine ID. Reason being this is a US website. Yamaha US did not offer a 40 HP two stroke in 2013. Last 40 HP two stroke offered by Yamaha US was in 2005/2006.

What type of over temperature indicator does the motor have? Is it on a tachometer or a separate light in the boat? Or is it a warning light on the motor?

If there was a real over temperature situation a buzzer should have sounded an alarm and the motor should have gone into RPM reduction mode. Neither of which seem to have occurred.

[HugoBoater]

Thanks for your swift reply. I'm living in Australia so that explains why it's not sold in the US.

It's a tachometer on the dashboard. I was only running the motor slow so it's hard to say if it limited the rpm.

I have attached pictures of engine ID and the tachometer.

[boscoe99]

What is the buzzer doing? Does the buzzer work? Pull the kill switch so that the motor will not start. Crank the motor. You should here the buzzer.

The motor has oil injection correct?

The tachometer is not set up in the two stroke mode. There should be symbols shown above the oil pot icon. That might be causing the alarm. Set the tachometer as shown in the diagram below and then see what happens.