The Jeanneau Sun Odyssey 509 2011 vs Jeanneau Yachts 51 2016 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.
On paper these two are close siblings in the size department — Jeanneau Sun Odyssey 509 2011 at 50,6 ft versus Jeanneau Yachts 51 2016 at 50,6 ft. Weight tells a clearer story for trailering families: the Jeanneau Yachts 51 2016 tips the scales at 31 747 lbs — 1 103 lbs less than the Jeanneau Sun Odyssey 509 2011 at 30 644 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 110 hp, the Jeanneau Yachts 51 2016 has a 35-hp advantage over the Jeanneau Sun Odyssey 509 2011's 75-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Both carry nearly identical fuel loads — 63 gal and 63 gal — so range won't be a tiebreaker here.
Both boats are rated for 15 passengers — a good fit for a family of four or five plus guests. Comfort at capacity is another matter; the longer hull typically means more seat options and better weight distribution.
Both boats sit in a similar displacement bracket — 30 644 lbs for the Jeanneau Sun Odyssey 509 2011 and 31 747 lbs for the Jeanneau Yachts 51 2016. Comparable displacement means broadly similar seakeeping behaviour and load capacity, though hull form and ballast ratio will still produce noticeably different sailing characteristics.
Both boats draw a similar depth — 7,6 ft and 7,6 ft respectively. Marina access and anchorage options should be broadly equivalent between the two.
The Jeanneau Sun Odyssey 509 2011 uses Sloop rigging. For auxiliary power the Jeanneau Yachts 51 2016 carries a 110-hp engine against 75 hp on the Jeanneau Sun Odyssey 509 2011. Motoring range and ability to punch through a foul current or enter a tight marina under power will favour the more powerful installation.
Hull speed is rated at 9,1 knots for the Jeanneau Yachts 51 2016 and 9,1 knots for the Jeanneau Sun Odyssey 509 2011.
Bottom line: The Jeanneau Sun Odyssey 509 2011 and Jeanneau Yachts 51 2016 are closely matched on paper. A sea trial on both in representative conditions is the only reliable way to find which one suits your sailing style, home port, and intended cruising ground.