Coolant temperature at idle rpm on Yanmar 4JH5E

[jjorio]

Hello everyone,

I transfer here my previous thread regarding my false-diagnostic on my Yanmar 4JH5E.

So here are the facts :
- Yanmar 4JH5E installed new in 2011. 1500 hours now
- After 25-30 minutes at idle rpm (around 800 rpm) the temperature alarm fires
- When navigating, there is no problem (Done 6 or 7 hours trip)
- No suspicious smoke
- Checked the impeler (recently changed anyway), OK
- Cleaned the raw water strainer, and the water at exhaust seems in reasonable volume
- The temperature at the top of the engine during those 25-30min clearly rises, and is too hot to touch at the end
- At exhaust, the water spit by the engine is suspectedly cold ... this water is not cooling the engine ...

Any clue where should I start from ?
Why only at idle ?
Thanks everyone
Jaad