The Riviera 645 SUV 2021 vs Riviera Yachts 51 Flybridge 2007 comparison sits squarely in the category of decisions where specs alone won't tell the whole story — intended use, storage, and long-term ownership costs all factor in.

Size is the most obvious dividing line here. The Riviera 645 SUV 2021 measures 69,8 feet overall (2021), giving it roughly 15,8 additional feet of deck space compared to the Riviera Yachts 51 Flybridge 2007 at 54,0 feet (2007). Weight tells a clearer story for trailering families: the Riviera 645 SUV 2021 tips the scales at 88 119 lbs — 87 667 lbs more than the Riviera Yachts 51 Flybridge 2007 at 452 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 1 400 hp, the Riviera Yachts 51 Flybridge 2007 has a 100-hp advantage over the Riviera 645 SUV 2021's 1 300-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Riviera 645 SUV 2021 carries 1 717 gallons versus 713 gallons in the Riviera Yachts 51 Flybridge 2007. 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 Riviera 645 SUV 2021 is rated for 21 passengers, while the Riviera Yachts 51 Flybridge 2007 caps at 16. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Riviera 645 SUV 2021 could be the deciding factor.