I have got to Parsun-4-stroke outboards, one 9.9 and one 15 hp. Both engines are "identical" to a 2002 Yamaha 15 hp 4-stoke, also the carburetor in both are identical to Yam-15.
My problem is that both engines performs identical, both acting like 9.9 hp.

The question is if anyone out there know what the difference shoud be, e.g. changing jet or nozzle in the carb, new exhaust-system, bigger air-intake or ???

When both engines seems to be identical I suppose it should be possible to get 15 hp out of each.
:-) Norwegian Water