The Beneteau First 51 1986 vs Beneteau R/C 42 1981 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 8,0 additional feet of deck space compared to the Beneteau R/C 42 1981 at 43,4 feet (1981). Weight tells a clearer story for trailering families: the Beneteau First 51 1986 tips the scales at 28 660 lbs — 6 283 lbs more than the Beneteau R/C 42 1981 at 22 377 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 30-hp advantage over the Beneteau R/C 42 1981's 50-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 40 gallons in the Beneteau R/C 42 1981. 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 R/C 42 1981 caps at 13. 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 6 283-lb difference over the Beneteau R/C 42 1981 at 22 377 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 5,7 ft for the Beneteau R/C 42 1981. That 3,5-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 51 1986 uses Sloop rigging. Helm style differs too: the Beneteau First 51 1986 uses a 2 wheels versus a 1 wheel on the Beneteau R/C 42 1981. 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 50 hp on the Beneteau R/C 42 1981. 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 8,1 knots for the Beneteau R/C 42 1981. For extended cruising, water capacity matters: the Beneteau R/C 42 1981 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.