Rudder Cavitation

[archangel73]

I would be interested in opinions regarding rudder cavitation. According to my mechanic, it is typical of boats to have some rudder cavitation. I noticed some markings on my rudder when we hauled out, and was wondering what the group thought of this. Props are fine, and no unusual wear/tear anywhere else. I just want to make sure everything I can do to prevent this, I am.

Thank you,

 

[dpmulvey]

Never heard of it.

 

[2000SR380]

What I know about cavitation burns on rudders is that it is almost always caused by a prop that is incorrect, or correct but out of spec.
It is mostly a concern for Inboards, not outboards or Inboard/Outboards. It costs a lot of duckets to true and balance a shaft, and propeller.
From the picture the damage on the rudder looks pretty extreme. I would still think about showing that shot to a Propeller Shop. In Alameda we have www.bay-shipcom/propeller-shop.html I am sure you have similar business that is closer to Kenosha, WI

 

[NorCal Boater]

I don't see any kind of sacrificial anode on your rudder. Without a closer look it's hard to tell but could it be electrolysis?

 

[Creekwood]

IS it just me or does that prop look a bit "wonky"? That lower right blade looks off. Maybe just the camera angle?

 

[PlayDate]

I'm with David.....I didn't know what this was. If you Google it you find tankers and all sorts of big boats with what looks like a corrosion issue on the rudder. There are even companies professing to make coatings (which look like hard bottom paint) to reduce the friction. I don't doubt it is a problem on a boat running 24 hours a day but I would think making sure your grounding system is properly connected may be more relevant to recreational boaters.

 

[KnotEasy]

It does not look like cavitation erosion. More like stray current issue. The Prop also looks fishy.

 

[Woody]

I don't know anything about it either. Where is this wear that's being question? What you guys looking at?

 

[bahamabreisus]

I dont believe Sea Ray uses zincs on rudders, we dont have them, or a place for them. Check bonding wires.

 

[2000SR380]

I dont believe Sea Ray uses zincs on rudders, we dont have them, or a place for them. Check bonding wires.

Our 380DA does not have Zinks on the rudders. There are zinks on the Prop shafts, and on the trim tabs. I believe the rudder system is bonded in the engine room.
I looked at some old pictures and my propellers look wonky in photographs as well. I learned about prop tuning because we drove over our own bloody bow line on New Years Eve a couple of years ago. NEVER do that! Because the line is attached to a cleat on the bow, it wraps up on the shaft toward the through Hull until it forces the shaft down and chunks out fiberglass. (and it happens right in the narrow entrance to Pier-39). By the time we were done fixing the hull, re-pitching the props, straightening the bent shaft, and 'Might as well' install new dripless seals and new strut bearings, the Yard Bill topped $6K. Making that one small error my most expensive laps in Seamanship ever. Had a epic night! Boat still drove great. My crew (that left the line in the water) redeemed himself later by saving some girl from getting a beat down on the dock, so we had fireworks, and drinking, a rescue, and an epic fist fight ending with a gazillion SFPD. After a couple of hours of sleep, We had a great Breakfast at The Crepe Cafe' and a beautiful ride home from Pier 39. All in all, it was almost worth the $6k

 

[archangel73]

I will check the bonding wires this weekend and ensure the rudders are protected correctly. If it is a stray current in my slip, won't it be hard to isolate where it is coming from? Any suggestions on how to determine the source of the stray current.