Yanmar YM coolant leak
I'm starting season 3 with a Yanmar 3YM20, and it leaks coolant. There's always a little under the engine, but a tiny top-up twice a season has seemed plenty.
I changed the coolant the other day, as recommended/required, and as I was removing the pressure/filler-cap on the heat exchanger, loosening hoses/bolts, the leak intensified, and then became a very steady drip for a minute. It was just behind the crankshaft pulley, right on the front of the engine, very localized. I could not find a trail of it dripping from higher up somewhere, and at that point I had just detached the "fresh-water" hose on the front of the engine to do an initial drain.
So, that's weird. The system leaked when I de-pressurized it.
Since re-filling, I ran it for a while and then had to top it up a bit again - normal, I believe - but haven't actually seen any leaking.
Still, this worries me. I have a year to go on the warranty, I think, so am going to look it over one more time and call the installing mechanic, which is a nuisance (5-hour boat-trip away, although of course only 40 minutes by land, and he does do "marina-calls" ...).
I come across various Yanmar coolant leak pages on a web search, but nothing so far definitive that tells me what to do other than call for professional help.
Anyone familiar with this scenario?
Oh, and ... a vane broke a year ago on the impeller, so of course I replaced it and the new one has been fine. I took advice including from the mechanic and it was that it's all okay, but now he says it's not okay and I have to find the vane - which I will do (or he will if I can't). Connection with the coolant leak? They're different sides of the cooling system.