Conceived to compete under either the ILC 46 class or the straight IMS rule, the boat puts rating and speed ahead of accommodation and cruising comfort. It displaces 18,500 pounds, including 11,000 pounds of lead in a deep, high-aspect fin. That gives it a ballast-to-displacement ratio of 59 percent. Sail area is 1,195 square feet, for an SA/D of 27.33—powerful, though not radical by modern raceboat standards.
Design and Intent
The Nelson Marek 46 was drawn specifically for measurement-system racing. Its IMS hull is smooth and free of any transition area, almost boring in its fairness. It has a fine entry, while the midsection shows no deadrise anywhere.
The deep fin provides the stability needed to carry the large sail plan. Filling out the stern adds further power. A D/L of 139 and an L/B of 3.42 place the boat firmly among light-displacement, beamy racers. Its waterline measures 39 feet 3 inches, and its draft is 9 feet 2 inches, reflecting a design optimized for reaching and running within rule-driven constraints.
By then, the Nelson/Marek office had already produced a large number of dominant IMS boats racing across the country. The 46 belongs squarely to that lineage.
Construction
Carroll Marine built the 46 in fiberglass and Kevlar, with a solid fiberglass hull and deck and a lead-ballasted fin. The interior components were vacuum-molded and integrated with the structure, so they contribute to the hull’s overall stiffness rather than simply furnishing it.
Weight is concentrated amidships to satisfy the IMS rule without slowing the boat. That priority also explains the minimal interior: the structure was designed to be stiff and light first, habitable second.
Rig and Handling
The Nelson Marek 46 carries a masthead sloop rig with four spreaders, runners, checkstays, and short jumpers at the hounds. It’s a thoroughbred arrangement that demands attentive tuning.
The fractional-style headsail setup reduces the need for headsail changes and eliminates the requirement for a huge foredeck hatch. The mainsail roach overlaps the backstay by about six inches. Mainsail controls lead to consoles on both port and starboard, allowing the crew to adjust sail shape from the weather side.
A huge open cockpit extends to the transom, giving the trimmer plenty of room to work. Steering is through Edson’s Spectra line-and-spool system, chosen for light weight and sensitivity.
Under power, a 50-horsepower Volvo diesel drives a saildrive unit. This combines the propeller shaft and strut in one clean assembly, concentrates weight near the middle of the boat, and places the unit in the keel’s wash to reduce drag compared with a conventional shaft, bracket, and propeller.
Accommodations and Tankage
By cruising standards, the interior is minimal. The vacuum-molded components serve a structural role before they provide creature comfort, and the concentration of weight amidships further shapes the layout.
Tankage consists of 40 gallons of water and 20 gallons of fuel. Those figures reinforce the boat’s race-first priorities rather than suggesting any ambition for offshore autonomy. A buyer expecting a roomy cruising layout will instead find a spartan shell equipped to make sail and win under rating.
Verdict
The Nelson Marek 46 is a focused IMS weapon: light, stiff, and beautifully fair, with a deep fin and centered weights that allow it to carry a generous sail plan. It isn’t a cruiser with racing pretensions, but a racer with just enough interior to be legal.
For an owner who values rating-correct speed and structural honesty over galley count, it remains a clean, purposeful 46-foot hot rod.
Pros
- Deep, high-aspect fin and 59 percent ballast ratio provide strong stability
- Vacuum-molded interior components contribute to a stiff, light structure
- Saildrive in the keel wash reduces drag compared with a conventional shaft
Cons
- Minimal interior, with only 20 gallons of fuel and 40 gallons of water
- Four-spreader rig with runners and checkstays requires constant attention to tuning
