Thanks for this. My Yanmar 3GM30 seems to be periodically getting air blockages. The overheat alarm went off last Thursday after a long sail, no water being pumped out of the exhaust. I undid the cooling pump inlet which flowed water, then the outlet which flowed water. Restarted and everything worked fine. Very peculiar!
Ooh. That sounds very similar to a problem we had last summer..! during our sail the water drained out of the cooling system, which is not unusual in rough weather or if you have a long sail, but on start up, our pump didn't have enough suction to self prime. It might be worth watching our video on the incident. Have a watch and let me know in the comments if it helped. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-X4tAsHm8Zcg.html
The volvo manual says to lubricate the impeller with glycerine only. I guess that is what the volvo lubricant is? I have stopped using vaseline on O-rings, these days I use silicon grease or the oil or fuel it will be sealing. By the way thanks for a very helpful series of videos on the volvo D series engines. Are you going to do one on cleaning the heat exchanger? That is MY next challenge.
You are correct. The lubricant that's included with the impeller kit is glycerine. The main reason I still use vaseline is because the glycerine is runny. The vaseline stays where you put it, which is useful when fitting a new impeller. I would definitely concede that the manufacturer's recommendations are always the one you should go for... Even if that's just to make sure there's no wriggle room with insurance company payouts.
