I agree, I think hp makes a difference. I had a 9.9 merc and it pushed noticeably better than my current 8 yami. I also tried a 6 yami and it was too slow. I like my 8 the most because it idles slower than the 9.9 so I no longer need to deploy drift socks when trolling and I no longer have to shift back and forth to neutral to slowly work my stuff down when back trolling down the river. A really slow idle is very nice and my yamaha 8 is much slower than my merc 9.9 was (granted the merc pushed up river slightly faster)