A specification document is the bridge between a brief and a built boat. Done well, it eliminates ambiguity at every contract milestone and gives both yard and owner a single reference for acceptance. Done poorly, it surfaces as change orders, schedule slip, and a delivered boat that nobody is happy with. This page covers the structure of a usable tender spec.
What sits in the spec
A good tender spec covers eight areas. Each section runs to a page or two on a custom build, less on semi-custom.
1. Mothership and operational role
- Mothership name, length, and beam.
- Garage dimensions: length, beam, headroom, deck loading.
- Davit class and lifting capacity.
- Cruising programme and primary geography.
- Role mix: guest transfer, beach landing, water-toy support, chase, SOLAS, crew shuttle. Rank by frequency.
2. Hull and dimensions
- LOA, beam, draft (engines down and up).
- Dry weight (target, maximum).
- Hull material (GRP, GRP-Kevlar, carbon, aluminium).
- Deck material (GRP, teak, synthetic teak, composite).
- Hull form (deep-V deadrise, twin-stepped, planing, semi-displacement).
- Owner colour-match specification with the mothership's livery code.
3. Drivetrain and performance
- Engine make, model, and count.
- Drive type (jet, sterndrive, outboard, IPS, shaft).
- Target top speed and cruise speed in named conditions (e.g. "Force 3, half load").
- Fuel capacity and fuel type.
- Range at cruise.
4. Capacity and certification
- Guest capacity (CE Cat A/B/C or coded equivalent).
- Crew capacity.
- Classification (SOLAS, MCA, RCD, CE Cat).
- Flag-state coding requirements.
5. Layout
- Cockpit configuration (open, U-sofa, bar, cabin module).
- Helm layout: number of screens, manufacturer, position.
- Stowage: locker dimensions, fender storage, refrigeration.
- Bow geometry: cleats, anchor, locker.
- Swim platform geometry, boarding ladder, watermaker showerhead.
6. Equipment fit
- Navigation and electronics package.
- Audio system specification.
- Refrigeration capacity.
- Watermaker capacity (where fitted).
- Toilet (Vacuflush, manual head, none).
- Davits, lifting strop, certification.
7. Build-quality clauses
- Vibration limits at named RPM.
- Noise limits at named RPM.
- Cosmetic acceptance criteria for paint, gelcoat, joinery.
- Warranty terms.
8. Delivery and acceptance
- Sea-trial conditions and pass/fail criteria.
- Punch-list resolution timeline.
- Handover documentation: O&M manuals, certificates, spares.
- Delivery location.
What's typically over- or under-specified
Common over-specs we see: top speed in unrealistic conditions, fuel range that ignores typical loading, audio and entertainment systems that double the wiring complexity for limited owner benefit.
Common under-specs: dry-weight target (drives lifting compatibility), spares package, vibration and noise limits, and the cosmetic acceptance criteria for joinery and paint.
Who writes it
For semi-custom and production builds, the yard provides a base spec sheet that the owner annotates. For custom builds, we draft the spec in collaboration with the owner's project manager and a naval architect on the hull and lifting sections, then tender it to the shortlisted yards as the basis for fixed-price quotation.