Design and Construction
The hull is solid fiberglass, and the boat carries a wing keel with a draft that varies from about 4.92 to 5.22 feet depending on load anchor. At 45.5 feet overall with a beam near 13.6 feet, the 43 CC Mk III shows a length-to-beam ratio of 3.35, a proportion that makes her beamier and more roomy than 58 percent of comparable sailboat designs anchor. Her 26,000-pound displacement and 7,000 pounds of lead ballast produce a ballast ratio of 27 percent, which is higher than only 12 percent of similar designs — a relatively low ballast fraction that speaks to a hull form leaning on form stability and volume rather than deep-ballast righting moment anchor. The displacement-length ratio of 259 places her among what one design database terms "moderate racers," with 42 percent of similar boats rated heavier anchor.
Rig and Handling
The cutter rig carries a sail-area-to-displacement ratio of 17.67, a moderate figure suited to a cruising boat of this weight. Standing and running rigging dimensions from period data show a mainsheet of about 113.8 feet and jib and genoa sheets of about 45.5 feet, all in 5/8-inch diameter, with a spinnaker sheet near 100 feet anchor. The wetted surface of the underbody is about 495 square feet, and the immersion rate runs roughly 1,680 pounds per inch, telling you how heavily she sits and how much she trims with tankage and stores anchor. On the stability side, the capsize screening value is 1.83, a number that by that formula alone would admit her to ocean racing anchor. The Motion Comfort Ratio of 32.1 means she is more comfortable in a seaway than 46 percent of similar designs anchor. Her theoretical hull-speed maximum is 8.0 knots.
Accommodations
Fresh water capacity is 681 liters, or 179 US gallons, a substantial cruising allowance that supports extended time aboard without frequent replenishment anchor. The center-cockpit layout that defines the Mk III name places the helm amid-ships, separating forward and aft cabin volumes in the manner typical of the type, though the berth counts and joinery details are not itemized here.
Known Issues
On several other Irwin models the builder used brass gate valves below the waterline in place of proper marine seacocks, and some earlier hull-to-deck joints were fastened with self-tapping screws rather than through-bolts — but those practices belong to other designs and eras, not to a documented condition of this one. A surveyor's normal pre-purchase routine remains the prudent path.
The Verdict
She is a beamy, volume-forward center-cockpit cruiser from Ted Irwin's own late-1980s design hand. Her moderate sail plan, wing keel, and low ballast ratio favor sheltered-water and coastal cruising comfort over offshore ballast-derived righting, yet her capsize screen and comfort numbers keep her credible as a passagemaker by the standard formulas. She is a large boat by any measure, with the tankage and living breadth that the center-cockpit brief promises.
Pros
- Roomy beam-to-length proportion, 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 for easy rigging planning
- Capsize screening value of 1.83, admissible to ocean racing by that formula alone
Cons
- Ballast ratio of 27 percent is low against peers, implying reliance on form stability
- Motion Comfort Ratio better than only 46 percent of similar designs
- No model-specific known-issue documentation to offset caution on older Irwin construction practices
