[roamertim]

Hello galvanic corrosion experts!

ON a recent boating outing, I had my aluminum Roamer beached next to 4 aluminum house boats. The fellow next to me ended up being extremely knowledgable about corrosion and aluminum boats. He even had a device rigged to assess galvanic current in the river around the boats and, to my pleasure, found that my Capac meter was reading exactly right (at mid ship location.)

In discussing protecting aluminum hulls, he brought up isolation of the shafts and props from the transmission. His boat has an electrically isolating plate between the shaft collar and transmission collars, with isolating inserts in one collar as well. My boat was re-powered in '87 and presently, has no such isolation. The shaft collar bolts up tight to the transmission collar, which in theory, certainly could provide paths for galvanic current.

Could you share whether your boats have such insulators? I do not know if such a ring was original on my boat or not. Perhaps the capac system was thought to eliminate the need??

THanks,
tim

[Northern Lights]

If it aint broke dont fix it. The boats electrically impressed corrosion control system - "Capac" made be Inglehard industries has sucessfully protected the boat since it was new. The argument is that you have two conflicting metal groups being protected by one system. The protective set point of the Capac is calibrated to protect the least noble metal in the common bonding / hull system. Decoupling the shafts electrically can be achieved. If you do you will need to install and maintain shaft zincs. The down side to leaving the boat as is, is that if the Capac was to be depowered or fail you would have your copper alloyed props, and stainless shafts now burning the aluminum hull for protection.
There is a wealth of information out there. Be careful who you believe as the dock wisdom on this subject is thick. There is a man in Ventura, Ca. by the name of Dutch VanderVort. He knows Capac, and knows aluminum hulls. If you want his contact info - contact me.