When two boats share the same hull type — in this case both the Mercury PT520 2008 and the Mercury PT650 2008 are inflatable rigid designs with inflatable construction — the buying decision usually comes down to a handful of practical questions: how many people are you putting on the water, how far do you trailer, and what does your tow vehicle weigh?
Size is the most obvious dividing line here. The Mercury PT650 2008 measures 21,0 feet overall (2008), giving it roughly 4,0 additional feet of deck space compared to the Mercury PT520 2008 at 17,0 feet (2008). Weight tells a clearer story for trailering families: the Mercury PT650 2008 tips the scales at 1 345 lbs — 684 lbs less than the Mercury PT520 2008 at 661 lbs. That difference is meaningful if you're working within a half-ton or three-quarter-ton truck's tow rating, especially once you factor in a motor, gear, and fuel.
The power gap is worth calling out. Rated to 150 hp, the Mercury PT650 2008 has a 50-hp advantage over the Mercury PT520 2008's 100-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Mercury PT650 2008 carries 79 gallons versus 19 gallons in the Mercury PT520 2008. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.
For family outings this is probably the sharpest distinction between the two. The Mercury PT650 2008 is rated for 19 passengers, while the Mercury PT520 2008 caps at 9. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Mercury PT650 2008 could be the deciding factor.
Bottom line: Choose the Mercury PT650 2008 if your priority is putting more people on the water — it handles 19 passengers and at 21,0 ft it has the deck room to back that rating up comfortably. The Mercury PT520 2008 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 9 that costs less to run day-to-day.