My boat, admittedly empty on fuel/gear and with 4 people on board, and its 2100 hr 225 hp gas engine, made 14 kts at just 3400 rpm but I couldnt get the old engine to turn any higher so have no idea what it might do at 4400 not that I want to run a 30 year old gas engine there anyway but maybe another few knots.
As Gurry says, they are not speed demons with round chines and a fat bellied hull with a wide keep and small prop aperture. Largest I will be able to fit is 19/20" prop. Also engine bay is shallow so you arent easily going to fit a big engine in there if you repower.
For me its perfect. I dont need to go too fast, just enough room for the herd to sleep in relative comfort, nice on a rainy day and efficient as any boat at 10kts or so. Will have to get back to you on the long term fuel numbers.
Go for a ride on it before buying anything. The layout is great for kids tho with high gunwales.