I have had two Yamaha 9.9 four strokes for a Catalina 27 since 1986. The
first engine was five years old when Hurricane Bob hit New England in 1991
and the engine got trashed by getting tangled up in a dismasted boats
rigging. It had alway run well and I had no question deciding to get
another of the same.
The four strokes are a bit larger in the power head than the 2 strokes - I
had to modify the engine well on my boat to allow the engine to tilt
upward. They are a bit heavier too - about 90-100 lbs for the Yamaha. A
nice thing in addition to the quiet, no oil smoke, and abilty to run at
idle for long periods of time is that they have decent charging capability
even at idle.
You should look at the Honda as well. They have a solid reputation for 4
strokes but for me I'll stick with what I know.