Thank you for that description, it captures in words the sound I heard very well. I will surreptitiously check that out next time I am on board. Perhaps when he needs to change an oil filter
again, I helped him do it last time.
I didn't want to be alarmist, but the last person who's boat I thought had cooling
problems ended up siezing and destroying their engine about two weeks after I expressed my concerns. (She had the guts to confess this to me after the event. Particularly brave as one of her regular crew members told me I was an alarmist idiot and that the cooling
Let's hope your diagnoses explains the noise.
I was not overly heartened when I asked a pair of boat mechanics I know over the weekend, and one of them replied... "What, strange noises from the Green Death?"