Design and Construction
The 43 CC Mk III measures 45.5 feet overall, with a beam of about 13.6 feet. Its length-to-beam ratio of 3.35 makes it beamier and roomier than 58 percent of comparable sailboat designs.
The hull is solid fiberglass, and the boat carries a wing keel. Draft varies from about 4.92 to 5.22 feet depending on load.
Displacement is 26,000 pounds, including 7,000 pounds of lead ballast. That gives the boat a ballast ratio of 27 percent, higher than only 12 percent of similar designs. It’s a relatively low ballast fraction, pointing to a hull form that relies on form stability and volume rather than deep-ballast righting moment.
The displacement-length ratio is 259, placing the Mk III among what one design database terms “moderate racers”; 42 percent of similar boats are rated heavier.
Rig, Performance, and Handling
The cutter rig has a sail-area-to-displacement ratio of 17.67, a moderate figure suited to a cruising boat of this weight.
Period data specify a mainsheet of about 113.8 feet and jib and genoa sheets of about 45.5 feet, all with a 5/8-inch diameter. The spinnaker sheet is about 100 feet.
The underbody has about 495 square feet of wetted surface. The immersion rate is roughly 1,680 pounds per inch, indicating how heavily the boat sits and how much she trims with tankage and stores.
The capsize screening value is 1.83, which, by that formula alone, would admit the boat to ocean racing. Her Motion Comfort Ratio of 32.1 means she is more comfortable in a seaway than 46 percent of similar designs. The theoretical maximum hull speed is 8.0 knots.
Accommodations and Tankage
The center-cockpit layout places the helm amidships and separates the forward and aft cabin volumes in the manner typical of the type. Berth counts and joinery details aren’t itemized here.
Fresh water capacity is 681 liters, or 179 US gallons. That’s a substantial cruising allowance, supporting extended time aboard without frequent replenishment.
Known Issues
On several other Irwin models, the builder used brass gate valves below the waterline instead of proper marine seacocks. Some earlier hull-to-deck joints were also fastened with self-tapping screws rather than through-bolts. Those practices belong to other designs and eras, however, and aren’t documented conditions of the Irwin 43 CC Mk III. A surveyor’s normal pre-purchase routine remains the prudent course.
Verdict
The Irwin 43 CC Mk III is a beamy, spacious center-cockpit cruiser from Ted Irwin’s own late-1980s design work. Its moderate sail plan, wing keel, and low ballast ratio favor comfort in sheltered waters and coastal cruising over ballast-derived offshore righting moment. Even so, its capsize screen and comfort numbers keep it credible as a passagemaker by the standard formulas.
This is a large boat by any measure, with the tankage and interior breadth expected from the center-cockpit brief.
Pros
- Roomy length-to-beam proportions, making it more spacious than 58 percent of similar designs
- Generous 179-gallon fresh water capacity for extended cruising
- Cutter rig with documented sheet and control dimensions to simplify rigging plans
- Capsize screening value of 1.83, admissible to ocean racing by that formula alone
Cons
- The 27 percent ballast ratio is low compared with peers, implying reliance on form stability
- Motion Comfort Ratio is better than only 46 percent of similar designs
- No model-specific documentation of known issues to offset caution about older Irwin construction practices
