Thanks guys for all the input. We had a Bukh
sail drive for years and changed the engine oil
every 100 hours. We always put the gear
shift into reverse when sailing to stop the prop spinning.
We had a saildrive
destroyed by electrolysis
as we unknowingly acted as the anode for a marina which had excessive stray current
. (The marina has now been upgraded with floating pens and all is well).
We now know when the sail drive anode is working as my captain
fitted an anode to the exterior of our hull
and wired the anode through a 50 milliamp scale meter to the engine
. This means we can easily see if electrolysis
is happening when we arrive in different ports
. This simple system saved us yet again when the automatic controller on an impressed current
cathodic protection system failed at a commercial
wharf - we were taking fuel
at the time and we very quickly departed but not before the prop speed had been blown from the tips of the propellor.
Now we are waiting for our new Volvo propulsion
to be installed, so this system will have to be rewired to attach to our new Volvo saildrive
as the volvo saildrive and engine are isolated from each other.
Perhaps this tip may save others from expensive replacements