Just came accross this, New 150hp 4 stroke from Mercury, its a naturally aspirated (no super charger) 4 cyl in-line with a displacement of 3.0 litres, the largest in its class, produces 164.9hp it has a single over head cam with just 2 large valves per cylinder to save on weight. It has an timing chain that needs no maintenance and weighs in at only 205kgs. Its conventional control cables to keep costs down. Saw these early pre-order prices in america, which look promising
150L EFI 4S MERCURY$9,700
150XL EFI 4S MERCURY$9,750
150CXL EFI 4S MERCURY$10,125
Looks like it would have the potential to be tweaked to 200hp in the future, which would be lighter than any 200hp outboard in a long time!
Heres the links i saw
Heres a link to a magazine article on the new engine---
New Mercury 150 FourStroke Outboard Debuts - features.boats.com