I had the top end valvles) of our 1985 Volvo Penta
MD17D rebuilt last year. The excellent mechanic
said that the lower end... rings were the cause of the grey smoke at start up. First time in the spring is rather smokey!
In my case the smoke stops or becomes almost invisible when the engine
get to operating temperature. There is almost no smoke when we start a warm engine
, and none when we restart the engine which is at operating temperature.
We do see steam occassionally especially when the air is cool. It is not white smoke as it disappates quickly.
I suspect your grey smoke is from rings or cylinder wall glazing as noted above... and probably subsides when the engine heats up.
I don't know that I would do the rings on this 22 yr old engine. I will tolerate the smoke as long as it performs well in all other aspects. It does.