I had a 1999 150 ficht. Top speed was a hair over 40mph on my 20 MA. My advice is to beat the living piss out of that motor during the first 30 days and get the bugs worked out. That motor needs to be propped to hit 6000rpm . . . 5100 is very very low. Blown the carbon out . . . it probably needs it.
http://www.boatsetup.com/Decarb_FICHT.html