Freshwater and Canal Boat Paint – Everything You Need to Know

Freshwater and Canal Boat Paint – Everything You Need to Know.

AuthorAndy Potts September 11th 2020 (reading time 7 mins)  





Maintaining freshwater boats such as narrowboats, yachts, fishing boats and cabin cruisers can be costly and time-consuming, especially if the paint job doesn’t go to plan. This guide explains how to achieve a professional, long-lasting finish that will enhance your vessel’s performance and protect it from the elements. Whether you’re a boatyard manager, repair shop sprayer or DIY boater, this article has your boat painting process covered.



Every good paint job begins with preparation we cannot emphasise this point enough, ensure you take time out to read through the paint manufacturers ‘recommended prep process’ on the technical data sheet prior to commencing any project. Cutting corners will result in an inferior finish that is likely to fail and expose the structure of your boat to the elements, reducing its lifespan.

Before doing any maintenance work, you’ll need to drydock your boat or take it out of the water so that you can prepare it from top to bottom.



Use a power washer and soft broom to remove dirt and build-up on large surface areas. Be sure to target any grime, sludge and oil with a suitable detergent. If you need to rid any surfaces of foul odours, try using a mix of baking soda and hot water. Rinse with clean water and allow to dry before painting.

Stabilising rusted surfaces and flaking paint 

The best way to remove rust and old flaking paint from your hull and large surface areas is with shot blasting equipment or a high-pressure washer. Allow the surface to dry completely and check for any remaining flaking paint edges. These can be sanded back and rinsed clean.



Removing rust from small areas and steel fixtures 

White vinegar or baking soda and a toothbrush will make easy work of rust stain removal and rusted steel fixtures. Cover the affected area in the vinegar or baking soda, allow it to sit for a few minutes and then scrub the dissolved rust away from the metal. Rinse the solution off with clean water and allow to dry before coating with a suitable rust-resistant paint.

Alternatives to blast cleaning your boat 

If blast-cleaning large areas is impractical for reasons of cost, safety or access to a dry dock, you can sand unstable areas of paint to create a sound surface. To remove rust, use a high-performance rust converter-primer such as Rustcoat to achieve excellent results with minimal surface preparation.


IMPORTANT NOTE: Avoid using wire wool and other steel-based tools on steel surfaces as they can cause further damage to already rust-damaged areas.


ultrimax-rustcoat-hull-paintBuy Ultrimax Rustcoat – 5 Litre



Buy Mirka Gold Velcro Sanding Discs P80 (100) – 150mm


Interior surfaces Ready For Boat Paint 

Sand all interior woodwork with an orbital sander to remove flaking paint or varnish and to create a key for strong adhesion. Wash sanded surfaces down with a suitable detergent and allow to dry before refinishing.


Buy Mirka Gold Velcro Sanding Discs P80 (100) – 150mm


Hull and roof repairs 

Bitumen is traditionally used to repair previously painted hulls and roof surfaces. It acts as a sealer to prevent water seeping beneath the damaged paint layer to the boat’s wood or steel surface below. However, as a single-pack paint, bitumen’s lifespan is short. Water friction will wear the thin 50-70-micron coating away within 1-2 years.

At Ultrimax, we advise our customers to switch to Jotamastic 90 instead. This two-pack marine grade epoxy mastic has several benefits over bitumen.

Benefits of using Jotamastic 90 

  • Adheres to any substrate – use it as a primer for all your boat’s surfaces, both above and below the waterline
  • Seals, protects and acts as an undercoat for any topcoats
  • Lasts 5- 10 years without recoating
  • Applying the recommended two coats to the hull gives you a minimum 200 microns dry film paint thickness for long-lasting protection against river abrasion
  • Available in most RAL colours so you can give your boat a modern finish in a colour of your choice

Application method:

Jotamastic 90 can be applied by brush, roller or spray gun, making it an ideal solution for professional sprayers and the DIYer.

Jotun-Jotamastic-90-marine-paintBuy Jotun Jotamastic 90


Boat paint for topsides

We recommend sticking with Jotun products above the waterline as well as below it. If you’re not familiar with the brand, it began its life as a marine and shipping paint supplier in Norway in the early 1920s. The cold, harsh Scandinavian climate provided the ultimate test environment, allowing Jotun to develop and refine some of the world’s best-performing marine coatings.



If you’re opting to use Jotamastic 90 on your hull and roof, you can apply it to your topsides too. Alternatively, Vinyguard Silvergrey or Pilot 2 will also provide a base coat that gives lasting protection against the elements.

Application method:

Jotamastic 90, Vinyguard and Pilot 2 can all be applied with an air-assisted, airless spray, brush, or roller.

Jotun-Jotamastic-90-marine-paintBuy Jotun Jotamastic 90

vinyguard-silvergrey-boat-paintBuy Vinyguard Silvergrey

Jotun-Pilot-2-5-Litre-marine-paintBuy Pilot 2


Topcoat – The Best Boat Paint?

Jotun Hardtop XP and Jotun Hardtop AX products offer high resistance to water on GRP, wood and steel boats. Hardtop AX has the highest gloss finish but can only be applied by spray. XP is still a high-gloss but can be applied by brush or roller.



For a more cost-effective option with similar wear ratings for marine, use Ultrimax Ultriprime as a basecoat followed by a topcoat of Ultrithane. These products can be applied using all methods, spray brush, roller.

Application method: 

Hardtop AX — spray only

Hardtop XP, Ultriprime, Ultrithane and Pilot 2 — these can all be applied by air-assisted spray, airless spray, brush or roller. You may need to add some ‘recommended thinners’ to help the product flow, especially if applying with a conventional spray gun.

IMPORTANT NOTE: Always use solvent resistant rollers; otherwise, the fibres will drop and damage the paint finish.


Jotun-Hardtop-XP-5-Litre-marine-paintBuy Jotun Hardtop XP

Jotun-Hardtop-XP-5-Litre-marine-paintBuy Jotun Hardtop AX

Ultriprime-Zinc-Phosphate-Primer-boat-paintBuy UltriPrime


Ultrithane-1K-Polyurethane-Gloss_3830Buy Ultrithane

Jotun-Pilot-2-5-Litre-marine-paintBuy Pilot 2



To give you vessel the showroom look, the ‘head-turner’ of the marina, finish your paintwork and plastics with a professional polish. We’re big fans of the easy-to-use 3M compound and polish system.



Painting the deck

After priming your deck with Jotamastic 90 along with the rest of your boat, we advise scattering Ultrimax anti-skid aggregate on the surface of your boat paint to create a non-slip finish. Topcoat your deck with a product that offers superior water, abrasion, solvent and chemical resistance, such as Jotun Hardtop Flexi or XP.

Application method: 

All these products can be applied with an air-assisted spray, airless spray, brush or roller.

Jotun-Jotamastic-90-marine-paintBuy Jotun Jotamastic 90

Jotun-Hardtop-XP-5-Litre-marine-paintBuy Jotun Hardtop Flexi

flormax-anti-skid-non-slipBuy  Ultrimax anti-skid aggregate

Jotun-Hardtop-XP-5-Litre-marine-paintBuy Jotun Hardtop XP



Brightwork is a less common feature of boats than it was, but you may still have woodwork to maintain such as handrails, toerails, caprails, steps, tillers and decking. Use a   to achieve the traditional high gloss effect.

Application method: 

Polyurethanes must always be spray applied in a spray booth.

Interior woodwork finishes for boats 

Painted wood

For interior woodwork such as kitchen and bedroom furniture and tables, we recommend something like Sayerlack Pu. This exceptionally durable 2-pack topcoat system delivers:


  • Excellent elasticity, UV stability and bonding properties for optimal protection
  • A choice of high-gloss, satin or matte finishes in a wide range of colours
  • Fast drying times

Lacquered wood 

If you are looking for a clear finish that enhances the natural grain of the wood, Sayerlack’s range of lacquer products is hard to beat for transparency and chemical resistance when used with a suitable hardener.

Application method: 

Air-assisted, conventional spray.

sayerlack-wood-paintBuy Sayerlack Pu

sayerlack-wood-paintBuy Sayerlack Lacquers



Need more boat painting advice?         



We’d love to help. Give our friendly Total Paint Shop Support Team a call on 01302 856666 or drop us an email at for more freshwater and canal boat painting guidance.

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Download: Ultrimax Catalogue                                       

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