We have almost identical boats. Same size/weight/engine/cuddy.
If he's getting 4400rpm with that prop it's about right on power wise. Top speed should be right around 42-45mph and cruising at 3000rpm at 25mph. 5 adults is about all the boat can handle weight wise, and if the "heavy" ones are sitting all the way in the back it will be tough to get on plane.
You have two choices, under-prop it to get better low/mid performance but sacrifice fuel consumption and top speed OR swap out the 5.0 for a 5.7. You can get a reman with warranty 5.7 with 300hp anywhere for around $2200 shipped, and you'll just need a 4bbl marine carb ($500) and the labor of swapping the blocks out ($1200ish).
Look around the used market.
http://tampa.craigslist.org/pnl/boa/4501568670.htmlPaying a mechanic "after hours" i bet the whole swap could be done for around $2000 with that motor AND you'll sell the 5.0 for $500-800. $1500 for an extra 100hp? Totally worth it. If I wasn't house shopping you'd see a thread on this site of me motor swapping my boat. Hopefully I can start on it this winter. 220hp in this sized boat is painful. 320hp would be insanely fun.