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Island Packet 31

1983–1989 · designed by Robert K. Johnson · built by Island Packet Yachts

The Island Packet 31 was designed by Robert K. Johnson as a shoal-draft coastal and near-offshore cruiser for couples and small families seeking safety, simplicity, and comfort over performance. Johnson's philosophy emphasized a full-length foiled keel with attached semi-balanced rudder, high freeboard, and a protected cockpit to create a forgiving, self-rescuing platform. The boat earned a reputation as a bulletproof starter cruiser — not fast, but difficult to get into serious trouble aboard. It targets the risk-averse cruising couple who wants to go far without a professional crew.

Check this first — draft depends on an option the name does not carry. The standard boat draws about 4ft on Island Packet's full-length foil keel, and a factory centreboard was available that takes it to roughly 3ft. The centreboard boat gains real thin-water access but adds a board, pennant and trunk to inspect and maintain, so it is a different survey as well as a different draft. Confirm which one this is.

This is a general read on the Island Packet 31 class — informed background, not a verdict on any individual boat. Condition, refit history, and how a particular hull was sailed and stored matter far more than class reputation. Use it to know what to look for; for a read on a specific listing, run a free FairKeel report on that boat.

At a glance

Hull form: Full Keel
Ballast type: Encapsulated Iron
Rudder: Keel Hung
Mast step: Keel Stepped
Hull construction: Fiberglass
Bridgedeck: Cored
Production: 1983–1989
Built in: USA

What the Island Packet 31 is known for

Full encapsulated keel eliminates bolt-on keel failure risk and simplifies the underwater hull — a genuine structural advantage for shoal-water and offshore work.
Shoal draft of approximately 4 feet (3 feet with factory centerboard option) opens a wide range of anchorages and tidal harbors unavailable to deeper designs.
Keel-stepped, well-supported rig with conservative sail plan is easy to handle short-handed and survives significant weather without drama.
High build quality and conservative engineering from Island Packet Yachts; hulls are known for longevity when maintained, with an active owners association and good parts availability.

Known trade-offs

Heavy displacement and full keel produce sluggish light-air performance — motoring is frequently required, placing a premium on engine reliability across all missions.
Original engines are 35+ years old on all hulls; many have deferred maintenance histories, making engine condition the single highest-risk variable at purchase.
Encapsulated iron ballast (not lead) is susceptible to long-term internal corrosion and expansion within the fiberglass shell — a survey finding on older hulls warrants serious investigation.
Cockpit and interior dimensions, while comfortable, are compact by modern standards — limited space for two adults on extended passages.
Resale market is narrow; values are sensitive to engine condition and deck integrity, and a neglected example can sit unsold for extended periods.

Age-related quirks to expect

Osmotic blistering on early hulls (pre-1988) severity: Medium affects: 1983-1987

Original Westerbeke or Universal diesel at or past service life — many hulls unrebuilt severity: High affects: 1983-1989

PolyCore deck moisture intrusion around chainplates and deck hardware — PolyCore is not balsa but can still absorb water at compromised hardware penetrations severity: Medium affects: 1983-1989

Standing rigging age — all hulls are 35+ years old, rigging documentation often absent severity: High affects: 1983-1989

Teak toerail and caprail fastening corrosion and wood checking severity: Low affects: 1983-1989

Systems to check before you buy

Engine and raw-water cooling priority: offshore, coastal, liveaboard

Original Westerbeke 27 and Universal M-25 engines are 35+ years old. Inspect raw-water impeller housing, heat exchanger, and exhaust elbow for corrosion and blockage. Oil and coolant cross-contamination is not uncommon on high-hour examples. A compression test and sea trial under load are mandatory.

Keel-to-hull encapsulation joint priority: offshore, coastal

Encapsulated iron ballast (not lead) set in concrete eliminates bolt-on keel failure mode but the fiberglass encapsulation shell can crack or delaminate, especially if the hull has grounded. Iron is also susceptible to long-term corrosion expansion within the encapsulation. Probe the keel-hull junction with a moisture meter and look for linear cracking or paint bridging.

Deck core and chainplate area priority: offshore, coastal, liveaboard

IP31 decks use Island Packet's proprietary PolyCore (resin and microballoon mixture), not balsa — so classic balsa rot is not the failure mode here. However water entry at chainplate knee bolts, stanchion bases, and genoa track can still compromise the core and laminate over decades. Tap the deck for soft spots and moisture-meter the chainplate knees. External chainplates simplify inspection and are a design positive.

Standing rigging and mast step priority: offshore, coastal, racing

Keel-stepped aluminum mast with compression post — check the mast partner for water pooling and the step for corrosion and fastener condition. Wire rigging on undocumented hulls should be assumed due for replacement. Swageless fittings are preferable on any hull going offshore.

Electrical system and bilge priority: liveaboard, offshore, coastal

Aging 12V wiring looms on 35+ year old hulls are frequently undersized, multi-spliced, and missing overcurrent protection. Inspect the main panel, battery cabling, and bilge for standing water or corrosion. AC shore-power wiring on liveaboards is a fire risk if original.

How it fits your plans

Offshore: Capable but slow offshore, with a forgiving motion and a self-steering-friendly full keel. The protected cockpit and high freeboard add sea-keeping safety margin. Engine reliability is the primary offshore risk — a verified repower is a significant upgrade on any hull going bluewater. Not a passagemaker's first choice, but many have crossed oceans aboard.
Coastal: Well-suited to coastal cruising. Shoal draft (around 4 ft, or 3 ft with optional centerboard) opens anchorages inaccessible to deeper fin-keelers. Predictable handling and easy single-handing make it an excellent coastal cruiser.
Liveaboard: Above-average liveaboard comfort for the LOA. High freeboard translates to standing headroom and reasonable storage. The wide beam carried aft gives a usable saloon. Systems maintenance burden is high on a 35+ year old hull — budget accordingly.
Weekending: Easy to manage short-handed, comfortable at anchor. Performance under sail is modest; motoring in light air is common. A good fit for relaxed weekend use where arrival time is not the priority.
Racing: Not a racing platform. Heavy displacement and full keel put it well outside competitive PHRF fleets. Omit from consideration for performance-focused buyers.
Motor: Motoring is a practical necessity in light air given heavy displacement and conservative sail area. Engine condition is therefore load-bearing for any mission — coastal or offshore alike.

This guide is the class. A report is that hull. Paste the listing you're looking at and FairKeel grades every claim in it against what's known about the Island Packet 31 — where the evidence is thin, the red flags worth a second look, the costs likely to land in your first season, and whether the boat suits the plans you describe in a few short questions.

It won't read the photos or put a number on the boat — that's the $249 Deep-Dive, and for the real answer, a surveyor. It will tell you when a Deep-Dive isn't worth buying. Free, no account, usually a minute or two.

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