Boat Maintenance Guide
Prep, Prime & Protect with International
A well-maintained boat starts with a plan. Whether you’re hauling out for seasonal upkeep or getting ready to relaunch, this guide takes you through the full maintenance cycle — from hull inspection and repair to fouling control and final finishing. Follow both phases for a boat that’s protected, performing, and ready when you are.
PHASE 1: HAUL-OUT & REPAIR
Get the groundwork done while your boat is ashore.
With your boat out of the water, you have clear access to every part of the hull. This is the time to inspect, repair, and prime properly - tasks that are difficult or impossible to do well afloat. Stable conditions and quieter yards make it easier to work methodically and get it right.
Step 1 - Clean & Inspect the Hull
- Start from the top and pressure wash the topsides and work your way down to underwater hull and remove any surface contamination and fouling.
- Scrape back loose or flaking coatings.
- Wash thoroughly with recommended boat cleaner to remove dirt, salt, and grime.
- Check for cracks in the gelcoat or flaking paint that may need monitoring or repair.
- If the gelcoat appears dull or chalky, consider buffing, polishing, or repainting
Step 2 - Inspect Below the Waterline
- Inspect the hull for osmosis — look for blisters that may weep a vinegar-like fluid.
- Take hull moisture readings.
- Examine the keel and rudder for impact damage, cracks, or coating detachment.
- If repairs are needed, grind out affected areas early to allow for proper drying before refinishing.
- Book any insurance surveys or professional inspections.
Step 3 - Repair & Prime
- Make necessary repairs to hull or appendages.
- Replace or reseal skin fittings.
- Prime exposed or bare areas.
- Service outdrives, sail-drives, and other underwater running gear.ms
Cast iron keels
Wash and grind back to bare metal, then apply a few coats of Primocon® early.
This protects the keel while ashore and makes re-coating easier when you’re ready to relaunch.
Rudders
- Inspect rudders for damage, especially at the lower edges.
- Drill out low spots for moisture to escape and allow to dry thoroughly.
- Seal GRP rudder damage with Primocon
- For shaping or filling, apply Epifill® filler.
- Once cured and sanded, reseal with multiple coats Interprotect®.
Step 4 — Interior & Timber Care
- Empty, dry, and clean lockers, storage areas, and bilges.
- While skin fittings are being renewed, refresh bilge or locker coatings with Bilgekote® for lasting protection.
- Remove lift-out timber items — cockpit seating, sole boards, hatches — and prep them somewhere sheltered and dry.
- Dry conditions are ideal for varnishing, saving you time when everything else needs attention closer to relaunch.
Phase 1 checklist:
✓ Pressure wash hull and remove fouling
✓ Scrape back loose or flaking coatings
✓ Inspect underwater areas for damage
✓ Take hull moisture readings
✓ Book insurance surveys or professional inspections (if required)
✓ Make necessary repairs to hull or appendages
✓ Replace or reseal skin fittings
✓ Prime exposed or bare areas
✓ Service outdrives, sail-drives and underwater running gear
✓ Clean and dry interior lockers, bilges, and storage areas
✓ Prep and varnish any timber items
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PHASE 2: RELAUNCH PREP
Get your boat ready to perform from the moment it hits the water.
Once repairs and priming are complete, it’s time to focus on protection and finish. This phase covers fouling control, propeller care, and topsides — everything that ensures your boat looks good and performs well once it’s back in the water.
Step 5 — Fouling Control
- Assess the current fouling control — if paint is flaking or heavily built up, consider stripping it back.
- Sand and prepare the surface before applying new fouling control paint.
- Choose the right antifouling based on local conditions, vessel type and usage.
- If switching brands, check compatibility charts — Primocon® is a vinyl-based primer suitable for application over most existing coatings.
- Don’t forget the propeller —Apply suitable primer for the propeller.
Step 6 — Topsides & Final Finish
Your boat’s topsides need protection too. The One UP® and Toplac® Plus system from International® offers:
- Faster application — fewer coats are required for a professional finish.
- Enhanced UV protection — helps maintain colour and gloss for longer.
- A smoother, glossier finish — no need for tipping with a brush.
Phase 2 checklist
✓ Assess and strip back fouling control if needed
✓ Sand and prepare hull surface
✓ Apply antifouling suited to vessel usage and local conditions
✓ Prime and antifoul the propeller
✓ Apply topcoat to topsides
✓ Final inspection before relaunch
Recommended International products
Primers & Barrier Coats
- Primocon® – Single-pack anti-corrosive primer with long overcoating windows
- Interprotect® – Two-pack epoxy primer for underwater protection
- Everdure - Two-pack timber primer for sealing and hardening against moisture absorption
- Etch Primer - Two-pack chromate-free primer with excellent anticorrosive protection and adhesion on aluminium
Fillers
- Epifill – Epoxy filler for above and below waterline use, including high -compression joints and deck fittings
Topcoats
- One UP® – High-performance topcoat primer for a faster, smoother finish
- Toplac® Plus – Durable gloss topcoat with enhanced UV protection
Discover the full International® product range for more solutions to support every stage of your boat maintenance project.