Do I need a thermostat?

[Smagu]

1984 yamaha 80hp pre mix 3 cylinder

First run out on it started having an alarm after 5 minutes WOT. I assume must be overheating/ Had a good tell tale and water 4 degrees Celsius. Have no gauges or tacho. I bought the engine after sitting for a few years.

Got a new thermostat, flushed with salt removal agent, have a new impeller to fit.

When removing thermostat cover I noticed it doesn't have a thermostat just an empty hole.

Should I leave it as or replace with my new thermostat?

(Have some time off work so got a few thread for this engine at the moment)

[jeffstevens763@g]

The stat is to keep your engine at optimum temp for it to run and burn fuel efficiently you choice really.

[paintman]

And can also control the route of the cooling water.

So fit the new one.

[Fenlander]

Ditto... always keep one in or refit if missing.

[Tommy c]

If it's been removed due to over heating, looking at the photo this could be because the water galleries are choked up with salt build up.
It looks like the remains of the old gasket have been left on too

[Tommy c]

This was how mine looked.
Even after fitting a new thermostat the telltale was still hot.
It wasn't until I removed all the salt build up that it started to run with a luke warm telltale.
Think my thermostat operates at 40⁰c

[Davie]

Originally Posted by Smagu

1984 yamaha 80hp pre mix 3 cylinder

First run out on it started having an alarm after 5 minutes WOT. I assume must be overheating/ Had a good tell tale and water 4 degrees Celsius. Have no gauges or tacho. I bought the engine after sitting for a few years.

Got a new thermostat, flushed with salt removal agent, have a new impeller to fit.

When removing thermostat cover I noticed it doesn't have a thermostat just an empty hole.

Should I leave it as or replace with my new thermostat?

(Have some time off work so got a few thread for this engine at the moment)

Has the poppet valve and spring been removed?

[Smagu]

Sorry I had removed the poppet valve and spring they were there.

Currently soaking everything in salt remover to try open up some of the ports. Not overly teen to take water jacket off. I will clean all up and install new thermostat.

I accidentally stood on the poppet valve and broke it in half (dooh!!). I have epoxied it back together and its looks pretty good. What exactly does the poppet valve do and will an epoxied together one do the job?

[Smagu]

Its maybe not as straight as it once was but seems very strong.

Want to put it back together and all the new ones seem to be from the states