The Beneteau First 345 1983 vs Beneteau First 51 1986 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 Beneteau First 51 1986 measures 51,4 feet overall (1986), giving it roughly 15,3 additional feet of deck space compared to the Beneteau First 345 1983 at 36,1 feet (1983). Weight tells a clearer story for trailering families: the Beneteau First 51 1986 tips the scales at 28 660 lbs — 17 416 lbs less than the Beneteau First 345 1983 at 11 244 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 80 hp, the Beneteau First 51 1986 has a 62-hp advantage over the Beneteau First 345 1983's 18-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Beneteau First 51 1986 carries 185 gallons versus 23 gallons in the Beneteau First 345 1983. 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 Beneteau First 51 1986 is rated for 15 passengers, while the Beneteau First 345 1983 caps at 11. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Beneteau First 51 1986 could be the deciding factor.

Displacement is where these two sailboats genuinely part ways. The Beneteau First 51 1986 displaces 28 660 lbs — a 17 416-lb difference over the Beneteau First 345 1983 at 11 244 lbs. That gap separates two entirely different categories of sailing: the heavier boat is built for offshore passage-making and load-carrying, while the lighter hull rewards performance sailing and easier handling in lighter air.

Draft is a practical consideration that many buyers underestimate until they're already at the marina. The Beneteau First 51 1986 draws 9,2 ft, compared to 6,2 ft for the Beneteau First 345 1983. That 3,0-foot difference affects which anchorages you can access, which haul-out facilities will take you, and how carefully you need to read the tide tables in shallower cruising grounds.

The Beneteau First 345 1983 is rigged as a fractional_rig_sloop while the Beneteau First 51 1986 carries Sloop rigging — a meaningful difference in sail handling complexity, upwind performance, and the size of crew you'll need to work the boat comfortably. Helm style differs too: the Beneteau First 345 1983 uses a 1 tiller versus a 2 wheels on the Beneteau First 51 1986. Wheel helms give better leverage and visibility on larger boats; tillers offer direct feedback and simplicity on smaller ones. For auxiliary power the Beneteau First 51 1986 carries a 80-hp engine against 18 hp on the Beneteau First 345 1983. 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 8,8 knots for the Beneteau First 51 1986 and 7,2 knots for the Beneteau First 345 1983. For extended cruising, water capacity matters: the Beneteau First 345 1983 carries 106 gallons versus 74 gallons on the Beneteau First 51 1986 — a significant advantage on longer passages where watermaker or provisioning stops aren't guaranteed.