our old prop eaten by electrolysis
our new prop
As we were sailing up to Cape Cod, there were a few issues that had developed. The port engine is losing about a quart of oil about every 15 hours of run time. The starboard rudder post and drive shaft began making a knocking sound. The wind indicator is hooked on something at the top of the mast. The new main halyard keeps twisting in the 2:1 block system. Which problem did we feel like investigating first?
The other day, Wil put on the swim mask and dove to check the cutless bearings on the starboard side. The cutless bearings seem fine, but there are definitley wobbles in the rudder post and drive shaft. He also was surprised to discover something else. Our zincs on the prop shaft were already significantly pitted. The boat has only been in the water for just less than 4 weeks and there’s already electolysis damage. This means we most likely have excessive electrical current leaking from our grounding system. There is a short or ground fault amidst our many wires running through the boat, and it must be tracked down and fixed immediately. The zincs will only be sacrificial for a limited period of time before the electrical current destroys our props and aluminum rudder housings.
When we were at the boat yard, we had replaced the rudder housing and bearing on the starboard side. The housing was a brand new piece of aluminum that we’d had fabricated. Now, we’re wondering if the quality of aluminum wasn’t up to standard for its purpose. Our electrolysis is bad and it has already destroyed the new starboard rudder housing, hence the rudder wobble. However, the prop shaft wobble is a separate issue.
Yesterday, we started the hunt for the electrical leak. We didn’t get very far before frustration set in. After some additional research, Wil has created a list of possibilities to explore today. This is going to take some time and it won’t be fun.
Finding your electrical leak that may be causing corrsion is not that difficult if you have the right tool. You need a Ag/AgCl reference electrode and a good User’s Guide. See http://www.boatzincs.com/corrosion-reference-electrode-specs.html.
Thanks for the info! That looks like a really cool tool. We are systematically going through every circuit, and correcting things as we go. We haven’t found the major leak yet, but we’re hoping it will pop up soon. If it doesn’t, then we’ll be ready to try something new. Definitely very frustrating.
We developed a regular knocking/banging from the rudder-post on the way back from The Scilly’s in a Bavaria40, but only in certain conditions.
Our conclusion/deduction for the knocking being partly caused by a following sea/swell coming from an angle causing us to corkscrew and pressure to build up then release on the rudder causing the bearings to “knock”.
There was no knocking in other conditions so whether it was also partly caused by worn bearings also is a question.
I crawled through the access hatch and had my hand on the rudder post as it happened several times and it felt as though it was being hit with a sledge hammer!
I found a few links to bearing problems (see below) but no other reference to our conclusion.
~Robin
http://www.bavariayacht.info/forum/index.php?topic=10.25
http://www.ybw.com/forums/showthread.php?t=181996
http://www.hr-parts.com/contents/en-us/Enderlein%2029-49.pdf
Thank you so much for all the info! Our rudder knocking was worse with following seas, even though we’d just put in new bearings and housing. It was tight prior to splashing in June. There is also a wobble in the prop shaft. For the time being, we’re only tending to the prop shaft, and saving the rudder post for later. But you’re right about the “it’s like being hit with a sledge hammer” on the rudder post. We will check out the sites you mention and see where it takes us. Thanks again!