Water Temperature Alarm

[muskie]

My Yanmar 1GM will trigger the water temperture alarm when it idle (after the engine ran for a while. i.e. an hour) But, if I starting the engine cold (still idle). It doesn't have the problem.

- I have checked checked the water inlet impeller is in a good condition
- Water coming out of from the exhaust normal when it's idle
- Water coming out of from the exhaust normal when it's running
- Water coming out of from the exhaust NOT normal (very little) when it idel (after engin ran for a while)

Any idea what is going wrong or what do I have to check next?

<hr width=100% size=1>

 

[longjohnsilver]

Check the impellor again, have seen one and heard of more which look good but on further examination the spindle? (metal bit in the middle) has come apart from the rubber, so spindle spins round but nothing else moves!

<hr width=100% size=1>

 

[Roberto]

Oil pressure?

Sometimes the same buzzer is used for water temperature and oil pressure alarms, are you sure the signal comes from the water sensor?

<hr width=100% size=1>

 

[muskie]

Re: Oil pressure?

I believe not the oil pressure since I can see on the panel that the water temperature light is "ON" instead of the oil pressure.

<hr width=100% size=1>

 

[oilyrag]

Could be the thermostat sticking/gunked up, but sounds more like some some of blockage/restriction in the cooling water inlet side. Do you have a filter/strainer on the cooling water inlet side which may be partially blocked?
Another possibility is that the rubber exhaust hose has collapsed inside - can still look ok from outside if this has happened.

<hr width=100% size=1>

 

[pete]

Also check the thermostat ( I have read that it can be fitted the wrong way around ) what temp does it open ? remove the sender unit and test what temp it is switching around 60 degrees (from memory) I have converted my 1GM10 to fresh water cooling and have had to fit a fresh water sender £49 inc delivery and vat (OUCH) good luck
Pete

<hr width=100% size=1>

 

[bob26]

Is the engine temperature normal as far as you can tell when the alarm sounds?

If it is, it might be a problem with the sensor. I know nothing of Yanmars but had this problem with Bukh 20. Bukhs are prone to such false alarms apparently (according to Mr Bukh anyway). The cause is electrolytic corrosion of the sensor and after fitting two new ones at £45 each in successive seasons I was advised to varnish the sensor head that is exposed to the hot salty water before fitting it.

A simpler cure was to pull the wire off the sensor so the alarm stopped...except that you spend the rest of the season paranoid and leaning over the stern testing the exhaust water temperature!

<hr width=100% size=1>