There's no point in going for a 150 . . . when a 200 weighs the exact same
Almost all two stroke 150 - 200hp v6 motors . . . are the exact same motor with different heads, carbs (unless EFI), exhaust, and sometimes porting and timing difference.
Yamaha 2.6L 150 - 200, 220 special, 225 excel.
Merc 2.5L 150 - 200 and old 2.4L Merc 175, 200, 220, 225.
OMC 2.7L 150 and 175 . . . 200/225 is a larger displacement motor.
The lightest V6 out of the bunch was the old 1979 2.4L Mercury 200/225 (331) followed by Mercury 2.4L 225 (360lbs) and mid 80's 2.4L 200hp (363lbs - Best Choice!!).
You can find all the weights on NADA.
http://www.nadaguides.com