It pays to keep the propeller clean
PUBLISHED: 09:00 03 January 2014 | UPDATED: 10:58 22 May 2017
Nick Hayward from Suffolk emailed:
This season I fitted a Darglow Featherstream propeller to my boat, which has been excellent, meeting all my expectations. I took advice and coated it with International Trilux antifouling, but at the end of the season this had come off in patches. Polishing the prop was then difficult as the antifouling was more resistant to the wire brush than a calcareous-type of deposit elsewhere. What is the accepted treatment in the Harwich waters?
As featured in the January / February 2014 issue of Anglia Afloat.
How long is a piece of string Nick? There’re almost as many techniques people use for cleaning propellers, as there are propellers. Harwich area waters are notorious for heavy fouling.
Generally marine growth on the propeller increases its surface roughness, greatly reducing its efficiency and causing vibration. Marine deposits lead to cavitation, which is the sudden formation and collapse of bubbles on the back of the propeller blades, and which can lead to severe erosion of the blades.
Reduced propeller efficiency increases fuel consumption by between 10 to 15 per cent, as the engine has to burn more fuel to maintain the same speed. Vibrations also lead to wear on the propeller shaft, bearings and seals.
There are a number of ways of cleaning off a propeller; mechanically, chemically and good old elbow grease. Mechanical methods include propeller-polishing pads, such as the 3M or Perago discs used in hand drills, while elbow grease involves a variety of scrapers and even an old chisel!
There is a danger, however, of scoring the surface of the propeller, especially with scrapers and chisels. The power discs need to be used with considerable care and afterwards you’ll need to ‘polish’ using around a 1200 grit wet and dry paper.
Chemical cleaning is far less abrasive, but depending on what you use may have some environmental repercussions. One trick I read of recently is to use brick cleaner (basically hydrochloric acid) poured into a plastic bucket, which is then hung under the prop. The chemical is then liberally brushed over and left to work. Repeat until the prop is clean. Dilute the contents of the bucket and dispose of safely, hose off the prop and shaft. Then polish.
Another even cheaper method is to take off the prop, place in a bucket containing a litre of vinegar topped up with enough water to cover the prop and leave to work for 24 hours. Repeat as necessary and wash off with fresh water and polish.
There are a number of proprietary products you can buy in the chandlers that claim to clean the crud off your prop; some work, some don’t but all are expensive. Better perhaps to work at the problem the other way round and try to prevent barnacles and crud forming in the first place; Lanolin grease is effective for about half a season and products such as PropShield are effective in the short term. You could also apply a resin lacquer that the barnacles have difficulty adhering to.