On a 1990 Yanmar 4JH 2 DTE 88 HP with 5000 hours we experienced a water cooling
The sound alarm
was out of order and we realised that there was a problem when we saw the white smoke in the saloon
(the engine is in the saloon's table, centered in the boat...).
We immediately stopped the engine and finished under sail (we were running under engine as the crew was exhausted, frozen and willing to be ASAP at the harbour at the end of a February cruise
After this incident, I decided to take the engine out of the boat and check it internally as we did not knew exactely how long the engine was running without cooling
I was fearing some damages in the cylinders and the piston heads, as well as on the motorhead.
The cylinders were absolutely intact and the motorhead straighteness was check and found OK.
We just changed the piston head
rings as it was easy to do at this moment, of course the bursted hose, and reconnected the sound alarm
It was during the first weeks we had the boat and has been, so far, the only incident we had with engine which can happen to anyother engine, the hose was not specifically a Yanmar part.
I was very surprised by the engine condition when we opened it and this enhanced a lot my confidence in Yanmar products.