Gillie - They look like a nice choice . . . lots of the same design features of the 150. I'd go for it if you are gonna keep the Seafari for a while.
Terry - It's funny (maybe not rational) . . . but I feel the same way about Yamaha and their use of gotcha metal parts i.e. "planned obsolescence". One rotten shift shaft ruined me on a 1989 motor. I'm sure folks with Yamaha 225/250 gut rot and speedy sleeve cranks or yamaha 350 Frisbee flywheels feel the same way. Do you have any pics of the wellcraft with twins?
Only time will tell if the newer Merc 4 strokes are built to last. One thing for sure it that they are not the same "dockbuster" design from the late 50's.