Tell tail temperature.

57paulimo · 19 September 2020, 15:08

Hi folks, firstly, thanks for all the help members have given me to get this far!
Following members advice regarding no flow at the tell tail of my Yamaha 70hp two stroke, ive double checked the impeller and water pump are nice and lubricated and running smoothly. Ive refitted the bottom end and dunked it into a much deeper barrel, which this time does cover the water pump.
It started up first time, and a good steady stream from the tell tail. Brilliant!
The problem is, after a couple of minutes this water got so hot that i couldnt put my hand under it!
Can anybody shed any light on this, bearing in mind the thermostat was new last year and the engine hasn't been used an hour since.
I'm hoping it might be just the stat getting up to temperature. I stopped the engine ( the alarm didn't go off), just until i know its normal (or not). Any help would be most welcome, (again)! I WILL GET THIS BOAT IN THE WATER THIS YEAR..........

Livid · 19 September 2020, 16:57

stat should try to keep the engine a 50c ish, it doesn't sound normal, telltale is never too hot to touch. check if the alarm goes again

paddlers · 19 September 2020, 17:38

Try running it with no thermostat . It should run cold constantly . Some people never replace their thermostat. I'm not recommending that but I have known thermostats even new ones to be suspect.

57paulimo · 19 September 2020, 17:47

Thanks for the replies, ive taken the thermostat out and dropped it into nearly boiling water, and the thermostat is definitely working.

spartacus · 19 September 2020, 17:59

Something isn't right, the telltale might be warm, but never hot. You can test the thermostat in a jug of boiling water. It's not a pattern part is it? You'll need a new gasket to refit.

I'd be inclined to check the cylinder head and water jacket if the thermostat checks out. Could be build up of salt. You can run the engine in Salt Away or white vinegar, but to be honest pulling it apart is the only wat to check properly.

You'll need a gasket kit for this too, plus head needs to be torqued from centre out in sequence.

Touching heads can be risky, with seized bolts, but right now you have an engine that's running hot, so not safe to use. PlusGas, heat and patience.

paddlers · 19 September 2020, 18:53

What's the result of running it without the thermostat in ?

Tim M · 20 September 2020, 09:08

Quote:

Originally Posted by 57paulimo

Ive refitted the bottom end and dunked it into a much deeper barrel, which this time does cover the water pump.

How long did you run it in the barrel for?

57paulimo · 20 September 2020, 11:50

It was running in the barrel for three maybe four minutes tops, until i switched the engine off!

57paulimo · 20 September 2020, 19:24

I'll try and get to the boat again this week, and try and run the engine without the thermostat.
Thanks for all the tips! All very welcome.

phoenixpete · 20 September 2020, 21:44

Quote:

Originally Posted by 57paulimo

It was running in the barrel for three maybe four minutes tops, until i switched the engine off!

Sounds to me that as you are running in a constantly recirculating body of water, ie not cold water, that the water in the bucket is getting warmer and warmer and will make the engine telltale hot. I bet if you run it in the sea or on a good hose it will be fine. I found this when running a solution of de scaler in a bucket with my Suzuki.

Tim M · 20 September 2020, 22:01

Quote:

Originally Posted by phoenixpete

Sounds to me that as you are running in a constantly recirculating body of water, ie not cold water, that the water in the bucket is getting warmer and warmer and will make the engine telltale hot. I bet if you run it in the sea or on a good hose it will be fine. I found this when running a solution of de scaler in a bucket with my Suzuki.

Exactly what went through my mind.