How well does propeller antifouling work? Yachting Monthly editor Theo Stocker tests Prop Defender over a full season to find out
Propeller antifouling tested: Prop Defender
Protecting a propeller from fouling is not easy, thanks to high prop speeds, but infrequent use.
There are three possible approaches to take; polished metal, slippery silicone based coatings, or biocidal antifouls.
By the end of the previous season, the generous fouling on the two-bladed fixed bronze propeller on our Sadler 29, Pasque, was costing us 1.5 knots under engine.
Last season, it was time to try something else and we decided to put a new glass-reinforced, silicone-based and hydrophobic product to the test.
Prop Defender creates a slippery surface to which fouling will struggle to stick, and should slip off when it does.
It uses non-aggressive primers, making it suitable for all metals.
It also contains no toxins, solvents, biocides or VOCs.
Application of the original product I tested is in three stages and proved to be pretty straightforward, though needs to be done carefully.
Start with a totally clean propeller before rubbing in the degreasing preparation paste with 180 glass paper pad.
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Next, scrub clean using the supplied detergent, and rinse off with fresh water.
Leave it to dry and don’t touch the metal with bare hands, as this can reintroduce grease.
I then applied the top coat with a brush – it needs 24 hours before it goes in the water and three days before use.
The company has since updated the product so it now has a two-stage hydrophobic top coat, which it claims makes the finish even more hard-wearing and slippery.
Verdict on Prop Defender
Our boat was in the water for a short six months this year and on the whole I was pleased with the performance of Prop Defender.
Our speed reduction from fouling was kept to a maximum of half a knot under engine, which is a good deal better than with bare metal.
During the main summer months, there was very little fouling to spot.
When we pulled the boat out of the water in late October, after a period of little use, there was very little weed or other growth, though more tenacious coral worm had been able to stick, and any other fouling had grown on this, rather than the metal.
Overall, it wasn’t a perfect solution, but a significant improvement on last season.
Coverage: 100ml or 2 applications for 24in prop
Includes: Prep paste, detergent, top coast x 2, stirrers, glass paper, gloves, brushes
Other propeller antifouling on the market
Hempel Ecopower Prop
A biocide-free spray, Ecopower Prop is used as a coating for propellers making it difficult for fouling to fully attach thus making it easy to dislodge and remove when cleaning.
It has a ‘self-renewing effect throughout the season’, and needs to be applied over a primer.
Price: From £22.99
Buy it now at Amazon (UK)
Buy in now at eBay (UK)
Buy it now at eBay (US)
Marlin Velox Plus Propeller Antifouling
A hard biocidal antifoul paint suitable for all metal types.
The active ingredient is zinc pyrithione, combined with soluble and insoluble resins to offer high adhesion.
It can be overcoated each season.
Price: From £43.95
Buy it now from Amazon (UK)
Propspeed claims to be ‘the original propeller and running gear coating system’.
It’s a silicone based topcoat that creates an extremely slippery surface.
Manufacturer Oceanmax recommends that it is applied by a professional applicator.
Price: From £349.99
Buy it now from eBay (UK)
Buy it now from eBay (US)