Her solid-fiberglass hull displaces 26,000 pounds and carries 8,000 pounds of lead ballast, giving a ballast ratio of 31 percent. The length-to-beam ratio is 3.35, while the displacement-to-length ratio of 259 places her firmly among moderate-displacement cruisers designed for load-carrying passage work rather than outright speed.
Design and Construction
The hull is solid fiberglass. The builder offered the 43-CC Mk I with either a wing keel or a fin keel, with draft ranging from about 4.92 to 5.22 feet depending on load. That moderate draft allows the 45.5-foot boat to enter most marinas.
With 8,000 pounds of lead ballast and a skeg-hung rudder, according to the builder’s specification, the underbody combines a conventional fin or wing keel with moderate draft.
The capsize screening value is 1.83, which indicates that the boat could, if judged by that formula alone, be accepted for participation in ocean races. Her Motion Comfort Ratio of 32.1 suggests a settled motion in a seaway for a vessel of this size.
Production began in 1984, placing the model before the yard’s late-period vinylester and improved-joint upgrades. No production-end year is stated.
Rig, Performance, and Handling
The 43-CC Mk I has a cutter rig and carries more rig than 96 percent of similar sailboats—a striking figure for a cruiser of her era. Her sail-area-to-displacement ratio is 17.4 with the ISO reference sail and rises to 20.7 with a 135 percent genoa. That gives her useful light-air drive without pushing her into the high-performance end of the spectrum.
The theoretical hull speed is 8.0 knots. Wetted surface is about 495 square feet, keeping the hydrodynamic footprint within a normal range for a boat of this length.
The standing and running rigging dimensions are generous. The three halyards are each 119.7 feet long and 14 mm in diameter. The mainsheet is 113.8 feet of 5/8-inch line, while the genoa sheets are 45.5 feet of 5/8-inch line. All are sized for the boat’s large foretriangle and boom.
An immersion rate of about 1,680 pounds per inch means the boat sits heavily when loaded but resists sudden changes in trim.
Accommodations and Cruising Capacity
As the model designation indicates, the 43-CC Mk I has a center-cockpit layout. According to the builder’s specification sheet, tankage includes 185 gallons of water and 107 gallons of diesel, showing that the boat was planned for extended cruising range and capacity.
The combination of a 62-horsepower diesel and a 13.58-foot beam suggests a roomy middle section rather than the pared-back interior of a stripped racer.
Survey and Ownership Considerations
Compared with cored hulls, the solid-fiberglass hull and simple keel choices should make survey and repair relatively straightforward. The conventional keels also keep the structure legible to any surveyor.
The Verdict
The Irwin 43-CC Mk I is a moderately loaded cruiser with an unusually powerful cutter rig for her type. Her wing- or fin-keel options provide moderate draft and good marina access. The comfort and capsize figures suit bluewater-passage aspirations, while the solid hull and conventional keels keep the structure readily legible to a surveyor.
Pros
- Cutter rig with more sail plan than 96 percent of similar boats
- Wing or fin keel drawing less than 5.25 feet, easing marina access
- Capsize screening value of 1.83 and Motion Comfort Ratio of 32.1, supporting offshore credibility
- Solid-fiberglass hull simplifies inspection
Cons
- Production-end year isn’t stated
