just got a 2013 621 300 offshore 9.9 kicker last fall after the 2 hour break in i couldnt be more happy with my choice in motors. Quiet Fuel dont really know yet like i said only 2 hours. full of gass no gear and one other guy 63.5mph with out touching the jack plate. yes when i start puting some things in it will i lose some speed yes. I didnt buy the boat for speed. I went Yamaha for reliability over anyother motor. over all my serches the only thing i could ever find was yes old 4 stokes heavy. I never found anything with reliablity of motors blowing up. read some little things on 300hpdi but thats it. the boat just pops up out of the water. used to fish out of a skeeter 1950 200 hpdi this 621 gets on plan much faster than that boat.