Just lifted my 42 for the annual antifoul and check over, the prop is very pitted however the Anodes are hardly touched. On further insepection the prop has electrical continuity with the hull anode, the prop should be insulated via its rubber bush and it seems that the prop has been acting as the Anode! I am fitting a new prop, a Flexofold, and will replace all the Anode wiring and replace Anodes with a good make Zinc. I do believe the failure was caused by the failure of the rubber bush which allowed the prop to become ‘live’. The boat is 2007 vintage with less than 900hrs on the clock and the prop is the original Aluminium one, oh yes and the boat is fitted with a Galvanic Isolator.
My question is has anyone else seen the Alluminium Bavaria props corrode in this way?
Hi…Yes I appear to have had a similar problem on my 2011 fixed two bladed Volvo alluminium prop.
(See thread below)
Looking back at mine the only reasons that I can figure for the problem are;
. The prop was not properly bonded to the rubber bush
. The covering of the prop may have been compromised during cleaning, exposing the alluminium and thus being lower in the periodic table became the sacrifice
. Poor manufacturing somewhere along the line
Having now replaced the original prop with the Flexofold, which by the way performs like a dream. Did a channel crossing which there and back involved some 5hrs motoring and have nothing but praise for the prop.
However I have now bottomed out the corrosion proplem and other owners miht be interested in my findings.
The gearbox is insulated from the engine, as we know, but one of the plastic/nylon washers under the engine to gearbox bolts had split making continuity, the rubber bush in the prop had also gone meaning that the prop was acting as an anode as I originally thought. New washers are cheap and well worth checking occasionally.
I now regularly check for continuity between the engine and the gearbox and would recomend owners to do the same, it’s easy to fix and can save money. One other tip when fitting anode do not be tempted to use SS bolt but use galvanised and bond both bolts together inside the boat.