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Prop Anti-Fouling

I am preparing to launch my 8 knot trawler for the summer and I need some advice. How can I prevent my prop from getting covered with hard marine growth? We keep the boat in New London, CT and run it frequently (175 hours per season) and when I haul in the fall my prop looks like a biology experiment.  The hub is covered with 1 inch thick hard growth and the base of each of the 4 blades are covered. I am sure it has an impact on boat performance. What can I do before I launch to prevent this problem?

John Provencher

John:

Thanks for the note and question regarding marine fouling.  This is a pervasive problem in many areas around the country including my own home water of the Chesapeake Bay.  In the warmer summer months props, rudders and shafts often become heavily fouled in just a week or two.  There are a few proprietary products on the market that claim to prevent growth on props and other running gear along with some unconventional approaches that include everything from Sharpie-type magic markers to tobasco sauce spiked bottom paint.  Still other techniques include zinc and copper plating.  I haven’t directly or indirectly through my boat yard customers had much success with any of these.  The one approach that I have used with success involves abrading the running gear, preferably by lightly sand blasting, and then coating with an epoxy primer manufactured by Interlux called Interprotect.  The challenge faced by running gear antifouling treatments is their inability to adhere to the metal surface.  The Interprotect primer overcomes this problem by mechanically bonding with the profiled or roughened surface.  A hard, non-ablative antifouling paint is then applied over the primer, where it forms a chemical bond with the substrate.  (If you want the greatest efficiency, lightly sand the first coat of antifouling paint, apply a second coat and then lightly sand it as well.  Of, if you are having this work performed by your boat yard, ask if they can spray these coatings on using an airless sprayer, which yields an exceptionally smooth finish.)  I’ve used this running gear antifouling system on many vessels and the results have been quite good.  The combined mechanical/chemical bonding program works exceptionally well and can be expected to last, with seasonal light sanding and reapplication of the antifouling paint alone, for multiple seasons.   A detailed description of the process was covered in an article I wrote a few years ago for one of Passagemaker’s spring commissioning inserts.  If you don’t already have it, it can be obtained from PassageMaker’s back issue service.

Steve C. D’Antonio, Technical Editor