do a tag search here on DF140 for info on a specific problem they had years ago.
It was not a problem with "the aluminum".
I can tell you that, while I did have the specific problem detailed in my other thread, my motor is now 13 years old and has 1100 hrs and has no problem with the aluminum. It is used hard, in salt. I would replace it with a DF150 in a heartbeat when the time comes.
Also, I believe Yamaha had a similar exhaust manifold corrosion problem in certain models... and Mercurys just plain suck....
Just kidding, listen, every brand has had its problems. I really like Yamaha and Suzuki 4 strokes and zukis cost a few $1000s less.
IMHO V20s match perfectly with 150 four strokes, unless you're on a big flat lake and can run at 50mph, then a 200 makes sense