T8 steaming or smoking?

[camanobass]

I have a 2006 T8 and also a 1999 T9.9, both 4strokes on the same boat. The T8 either steams or smokes off and on but the T9.9 never does. I've had it to the dealer many times with many repairs, new carb, new thermostat, "de-carbonized" but it still smokes or steams (color is whitish). This last time to the dealer they had a Yamaha rep tell them that this was steam and was normal. A pressure test was done on the combustion chambers that was normal so they're convinced its not oil.

My question is why does the T8 steam and the 9.9 doesn't. Also the T8 gets a black drip stain below the small exhaust port where the 9.9 doesn't. I see lots of other T8's and have never noticed steam from them.