Cathodic protection and bonding

[Peter Lynch]

Hi,

Has anyone experienced corrosion problems with the Hunter 27? Our nearly new boat now needs a new prop and we are told it should have been "bonded" - a system of joining up similar sorts of metal so they corrode at the same rate. We are keen to hear if anyone else has experienced this problem in salt water? We are in Australia. Thanks

 

[Johnb]

My boat has zincs on the propeller shaft, support strut and propeller itself. I have had it suggested that the zincs on the strut are unneeded but as it came with the holes already drilled I have kept it that way. I pay for a diver to check things every 3 months and he changes zincs promptly as needed. In 10 years we have have had no corrosion problems.

An acquaintance with a power boat had a problem with AC power leakage and his stern drive unit was ruined in 4 weeks. This could also come from adjacent boats. This is something to look into, especially if you leave power on continuously.

Bye the way, what is the water temperature in Sydney?

 

[Bill Roosa]

Current wisdom on glass boats

is to unbond everything so it cannot corrode. Then protect those things (prop and shaft) that still have dissimilar metals in contact and a common water connection. A zink on the prop shaft is suffficient.
There is a great info paper on the west marine site under grounding

 

[Ken13559]

In the previous place I berth my boat, my prop pitted with lots of small holes and poke marks. Discover some shore power cable was in water and possibly leaking. After rework on electrical cable no more such problem. Shaft has always have zinc anodes but that got eaten up real bad (which was why prop got eaten as well) until the shorepower cable problem was fixed.