electrolisis

[hotrodderjim]

My boat is out of the water for the winter so I pulled the prop off( Yanmar/saildrive 2 bladed). It turns out that its very pitted from electrolysis!!
My question is: did the 1978 Oday tall rig(keel) come thru with some kind of ground plate? I thought it had some type of "painted" over block sticking down! I was wondering if that is a factory item.I'll go down & check tomorrow but I'm wondering.
Thanks
HRJ

 

[PaulK]

If it's painted over, no matter who put it there, a grounding anode is not going to work. Grounding plates are generally set up to help with lightning protection, not electrolysis issues. Zincs on the shaft are generally used to help keep electrolysis from affecting bronze propellers. If you don't have zincs on the shaft, (or wherever they go on your setiup) you need some. A '78 prop is likely to have had plenty of opportunities to get some pitting, Perhaps too many. Maybe it is time for a new prop, along with new zincs? Since you have it off already, take it to a trustworthy mechanic (or two) and get some input.

 

[hotrodderjim]

The engine & sail drive where installed in 2004 & the boat sat in a yard for 7 years until I bought it a year ago. There was a zinc on the housing of the sail drive. And the prop is alumn( Not the best thing to have in saltwater).I did paint the prop last spring & it wasn't pitted. Apparently electrolysis is a problem on sail drives & stern drives.
I just wanted to know if ground plates were installed on O'days.
HRJ

 

[Richard19068]

I doubt they came stock with a ground plate.

 

[hotrodderjim]

I doubt they came stock with a ground plate.

I'm going to go down to the boatyard to check it out. Its about 14o here so I'm not in too much of a rush! lol
Thanks
J

 

[Maine Sail]

Electrolysis is what hirsuit ladies have done to their upper lip.

You are suffering from what is most likely galvanic corrosion from lack of adequate anodic protection, or possibly from stray current corrosion such as a DC leak.. Aluminum saildrives are pretty notoroius for corroding easily & rather quickly, if not well protected.

 

[hotrodderjim]

Electrolysis is what hirsuit ladies have done to their upper lip.

You are suffering from what is most likely galvanic corrosion from lack of adequate anodic protection, or possibly from stray current corrosion such as a DC leak.. Aluminum saildrives are pretty notoroius for corroding easily & rather quickly, if not well protected.

How should I protect it?
HRJ
PS:electrolytic! My Bad

 

[Pat]

Our 272 has a grounding plate but as noted above it is for lightning I believe...any inboard needs to have a zinc collar on the prop and on our Westerbeke there are three pencil
zincs that need to be checked periodically...