Last week I posted a recent service bulletin from Yanmar regarding sail drive corrosion an their take on how to mitigate the problem. I’ve heard from a reader since and he makes a point worthy of further emphasis.
It can’t be stressed enough that one of the secrets to keeping your saildrive leg in one piece is to ensure that the anode to cathode relationship protecting the drive is adequate. In simpler terms, this means that the amount of anode has got to be large enought to effectively protect the amount of exposed aluminum on the drive.
One of the best methods of ensuring this is tilted in your favor is to use a tenacious coating of epoxy on the aluminum, effectively insulating it from the water it lives in. The Yanmar bulletin does say to use an epoxy barrier coating before applying the primer and anti-fouling paint. Our reader has spoken with several folks on this matter that have read the bulletin and apparently missed this key point.
So again, and following along with my much earlier articles here entitled “Keep Your Drive Alive”, the epoxy barrier coating is of paramount importance. Further, and a step I’ve seen many people miss is the proper cleaning of the drive surface before applying the barrier coating. The enemy here are invisible soluable salts (assuming the drive has been in salt water). These salts must be washed away before any coating is applied. The bulletin does mention both a test kit and a bio-degradable wash product available from Chlor-rid Corporation www.chlor-rid.com use them before you attempt to apply any barrier coating to your drive to ensure long term adhesion of the coating.