electrolysis

9mtrojan · Post by **9mtrojan** » Tue Apr 12, 2011 2:40 pm

Hi All,
When I pull the boat out 4 the winter I noticed that the starboard prop and nuts (inboard) were all pitted. Checked the port side and all looked good. Be4 I pull the deck up I'd like 2 know what I mint b looking 4 that would cause this on 1 side and not the other. Thanks All Paul

risctaker · Post by **risctaker** » Tue Apr 12, 2011 2:54 pm

Hi Paul. A couple of questions. Were the zincs all gone on the starboard shaft but still at least partially intact on the port side? If the zincs are completely gone then the running gear would be next on the electrolysis list. Does your boat have a bonding system? If so, is the bonding wire missing /corroded on the starboard side but OK on the post side? something to check. Post back the answers so we can dig a bit further.

Big D · Post by **Big D** » Tue Apr 12, 2011 4:37 pm

What risctaker said. If you didn't have any anodes to biggin with, get some on there. You may consider adding to some locations that may not have had anodes before such as rudder, trim tabs and diver's anode on transom (must be wired in). The more the better. If you have nieghbours, sounds like the one to starboard or the marina itself may have a stray current issue that is robbing your material. If you're in a marina, have them do a stray current test in the water around you. This will identify a problem if one exists.

Ever had the bottom acid washed? I've also seen the same thing happen just because one side of the bottom wasn't rinced well enough. Any acid left will pit some metal before going back in the water. It'll look like an orange peel. Other low lying hardware like swim platform bolts and supports, shafts etc may show the same signs as well.

9mtrojan · Post by **9mtrojan** » Tue Apr 12, 2011 4:58 pm

TY 4 the fast reply risctaker and Big D. the zincs looked just fine on both side on the rudders. The boat has a bonding system. I guess my next step would b 2 look at the wires like u suggested. Going 2 check the divers anode also. Last year when I tighten the nut it spun a little and maybe I broke the wire off. Possible right? Never had the bottom acid washed. I'm going 2 asked the marina about that stray current test. Wouldn't the boat next 2 me have the same problem on his port side? Thanks again. Paul

koviak · Post by **koviak** » Tue Apr 12, 2011 6:08 pm

This condition is called galvanic corrosion. Most of the time it can be traced back to your own boat. Check over your AC system ground and the outlet you plug into for shore power. DC side bonding also important, make sure all bonding wires are tight and free of corrosion. Something as simple as a bildge pump float switch leaking current into bildge water can cause this. You can also add shaft brushes to your bonding system to protect running gear. Galvanic isolater is a good investment to protect your boat from others at the dock. Automotive style battery chargers on boats will amplify this effect, they make marine use for a reason. Sorry if I got long winded !!!

prowlersfish · Post by **prowlersfish** » Tue Apr 12, 2011 8:15 pm

Did you have zincs on your shafts ? you said the ones on the rudders were ok but said nothing about the shaft zincs

9mtrojan · Post by **9mtrojan** » Wed Apr 13, 2011 3:05 pm

No zincs on the shaft. I tried a few time but they just came off. Tighten them as well as I could, tapped with a hammer and tighten again. Always feel off. I need 2 check the shore power side also on dock and boat. This just stared last season so it must of been something I did or knock off. Found 2 cables with the ends fraid and held on by 2 or 3 strains. New 1s put on. Thanks All Paul

gettaway · Post by **gettaway** » Wed Apr 13, 2011 4:11 pm

I had a set of shaft zincs fling off of mine last year, "economy brand" from west marine, changed to a more expensive shaft zinc, and no issue.

captainmaniac · Post by **captainmaniac** » Wed Apr 13, 2011 6:10 pm

9mtrojan wrote:No zincs on the shaft. I tried a few time but they just came off. Tighten them as well as I could, tapped with a hammer and tighten again. Always feel off. I need 2 check the shore power side also on dock and boat. This just stared last season so it must of been something I did or knock off. Found 2 cables with the ends fraid and held on by 2 or 3 strains. New 1s put on. Thanks All Paul

Are you sure they just 'came off'? Any chance you have sufficient issues that you are dissolving them?

9mtrojan · Post by **9mtrojan** » Thu Apr 14, 2011 8:02 am

I'm sure. While I was crusing heard a clunk and thought I hit something. Anchored up, checked 4 damage and it was not there. They were also bought from West. Going 2 check all suggestions this weekend and let u all know what I found. TY much. Paul

reelfishin · Post by **reelfishin** » Thu Apr 14, 2011 11:50 pm

Sounds to me that you stripped the bolts and they came off or maybe the shaft was not clean eough for them to have a tight fit.

prowlersfish · Post by **prowlersfish** » Fri Apr 15, 2011 6:52 am

It won't hurt to put 2 zincs on each shaft

risctaker · Post by **risctaker** » Fri Apr 15, 2011 11:37 am

Just had a diver check the underwater gear on "Basket Case" last night and he came up with a very good report on the general condition of things down there. There were absolutely no zincs left on anything but also no evidence of pitting or corrosion of any kind. I had him clean the shafts on either side of the struts and install double extra-heavy zincs. He did not have any rudder or trim tab zincs with him however and didn't know the size needed (??). Do any of my fellow 36' tri-cabin owners have the zinc sizes handy for the rudders and trim tabs? Also the diver said there was no center zinc on the transom (not sure what that one is for anyway).

prowlersfish · Post by **prowlersfish** » Fri Apr 15, 2011 12:03 pm

almost any size will work Its the shaft size that has to be exact

risctaker · Post by **risctaker** » Fri Apr 15, 2011 1:34 pm

OK Thanks. I have to assume that the bigger the longer they will last, but what about the hole size already drilled through the rudders and tabs? Aren't they for a certain size zinc? surely the larger ones have larger diameter bolts through them?