Using the wrong sealant is one of the most common causes of leaks, failed fittings and paint that won't stick. Fortified Oceanic in Newport, Sydney stocks marine sealants and adhesives from Fixtech, Sika, Bostik, Dowsil, 3M, West System and more for boats across Australia. This guide helps you pick the right product for the job.
1. MS polymer sealants: the all-rounder
MS polymer (hybrid) sealants bond and seal at the same time, stay flexible, cure underwater, and can usually be painted. That makes them a great first choice for deck fittings, hatches, through-hulls and general bedding. Our most popular is Fixtech FixSeal MSP15. For high-strength bonding, step up to Fixtech Fix 190HT, Teroson MS 9320 or the Bostik Simson ISR 70-03, ISR 70-05 AP and ISR 70-08 AP range.
2. Polyurethane sealants and adhesives
Polyurethanes form a very strong, tough, flexible bond, ideal for permanent joints like hull-to-deck joints and fittings that take heavy loads. Choose Sikaflex 292i, Bostik Matrix FC or Bostik Seal N Flex 1. Keep in mind that polyurethane bonds are very hard to undo, so don't use them on anything you may want to remove later.
3. Windows and hatches
Acrylic and polycarbonate windows need a sealant that won't crack the plastic and stands up to sun. Sika 295 UV is designed for bonding and sealing marine windows, used with Sika Primer 215 where the data sheet requires. For glass, structural glazing sealants like DOWSIL 795 and Fixtech Fix 8 are used, along with Teroson Glass Primer and Activator. Foam double-sided tape helps set the right bond gap.
4. Teak deck caulking
Deck seams need a caulk that sands cleanly, handles sun and foot traffic, and moves with the timber. Use Fixtech Fix 1DC Teak Deck Caulking or Sika 290DC Deck Caulking.
5. Silicones: use with care
Silicone sealants like Fixtech Fix 200 and Bostik V60 are good for weatherproofing and glazing, but they can't be painted, and silicone contamination causes fisheyes in paint. Keep silicone well away from any area you plan to paint or varnish.
6. Structural adhesives
Methacrylates like Crestabond and SCI Grip SG 100-40 bond metals, composites and plastics with very little surface prep, and are used for stringers, bulkheads and fit-out.
Epoxy adhesives: West System Six10 comes in a handy cartridge, while Techniglue HP, Megapoxy 69 and Rapid Cure 5 Minute Epoxy cover everything from structural bonding to quick repairs. Spabond 445 is also available for composite work.
7. Spray and contact adhesives
For headliners, foam, carpet and upholstery, use 3M 77, 3M 80, 3M 76 or Tensor Grip T65. For bigger jobs, Bostik Anchor-Weld comes in 20L pails.
8. Getting a good bond
Surfaces must be clean, dry and free of grease, wax and old sealant. Use 3M General Purpose Adhesive Cleaner to remove residue, lightly abrade where the data sheet says to, and use the recommended primer. Mask both sides of the joint with tape, tool the bead smooth, then pull the tape before the sealant skins over. Use CAM metal applicators for tooling and spreading.
Always follow the manufacturer's technical and safety data sheets. Not sure which sealant is right for your job? Contact the Fortified Oceanic team in Newport for advice and trade pricing.