Click for JetForums Click for Burger Click for Cross Click for Lurssen Click for Seacoast

Severe aluminum shaft log corrosion/deterioration

Discussion in 'Technical Discussion' started by Scallywag, Jul 22, 2012.

You need to be registered and signed in to view this content.
  1. Scallywag

    Scallywag Member

    Joined:
    Apr 25, 2012
    Messages:
    67
    Location:
    Islamorada FL
    Pulling the shafts yesterday revealed severe corrosion and deterioration of the shaft logs. Anybody have recommendations on 1.) proper repair procedure 2.) what could have caused this and how to prevent it?

    The boat is a 1992 custom 70' pilothouse built by Marine Builders in Indiana. Material is 5086 alloy aluminum. Shafts are stainless and props are bronze. Shaft seal is bronze.

    Attached Files:

  2. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    8,763
    Location:
    Satsuma, FL
    Yep, A case of the ate-ups. I would first look at your bronze shaft logs packing assembly. Were they bonded with the hull? Next maybe, ground brush on the shaft? AND, Steel in the log hose, Were the wires turned in to mate with the bronze gland and alloy shaft tube?
    Sorry friend, A case of the ate-ups. Probably been eating away on that shaft tube since it was built. Be glad you found it now, boats sink from this.

    Get a surveyor on board, good welder, correct materials and follow up survey. I'm sorry your going to spend some unexpected money, but again, be grateful you found it now.

    I had a similar case on an old Striker rudder post tubes. Converted to a Las-Drop system (all synthetic) and no more problems. You may have enough shaft tube to save the system and go to a synthetic log assembly like PSS or Las-Drop and do away with the bronze gland assembly.

    Keep up posted and send more pictures. We all learn more from our members.
    ,rc
  3. Bill106

    Bill106 Senior Member

    Joined:
    Jan 9, 2010
    Messages:
    389
    Location:
    Beaufort NC
    Unfortunately you are looking at a fairly extensive and expensive repair. Bronze cutlass bearings are a no-no in aluminum shaft tubes, even when potted in with Chock-fast there is usually an electrical connection to some degree that will swiftly eat the adjacent aluminum. Composite bearings and seals are essential to long life in those tubes.

    We just went through a shaft tube replacement on an older aluminum hull that a P.O had replaced the bearings with bronze and they were also corroded to the point of failure, most severe pitting was at the inside end of the bearings. Those tubes also pass through the main fuel tank (what kind of designer came up with that brilliant idea?). Tanks had to be drained cleaned and certified safe for hot work by a marine chemist. Here's a couple pics of the damage.

    Because it was outside our area of expertise, Ocean Alloys/Seaworthy Services in Palm Beach Gardens was contracted to make the repairs and I can wholeheartedly recommend them. They specialize in aluminum hulls and repairs and do this everyday. Before installation make sure you have them barrier coat the insides of the tubes which will greatly increase their life span, most OEM's suprisingly do not do this.

    Attached Files:

  4. Scallywag

    Scallywag Member

    Joined:
    Apr 25, 2012
    Messages:
    67
    Location:
    Islamorada FL
    Thanks for the input guys. I appreciate hearing your experience. I will be meeting with the welder tomorrow and I'll post updates as new information rolls in.

    Amazing the surveyor didn't notice the bulging log shaft hoses and broken hose clamps. Going through his report he even included a photo of the log hose, but never mentioned any possibility of a problem even though it was staring him straight in the face. Thanks to Pascal for bringing the issue to my attention!
  5. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    8,763
    Location:
    Satsuma, FL
    The hourglass shape of that hose, even in a plastic boat, is a signal for attention. I can not remember the outcome of a discussion a while back about bringing things like this back up with the surveyor. It may warrant a letter to the Society he belongs to. Was that a buyers, insurance or a good ol boy survey?
    I have discovered the hard way also, some surveyors have not a clue about steel or alloy boats. I recommend calling somebody else in the future.
  6. Scallywag

    Scallywag Member

    Joined:
    Apr 25, 2012
    Messages:
    67
    Location:
    Islamorada FL
    This was a BUYERS survey. Both the hull surveyor and mechanical surveyor missed this obvious issue. There was a laundry list of other items that should have been noted in the survey, but were missed.

    I'm amazed at who can call themselves an "accredited surveyor". The hull surveyor will be hearing from me once the repairs are completed and all the dust is settled.
  7. Scallywag

    Scallywag Member

    Joined:
    Apr 25, 2012
    Messages:
    67
    Location:
    Islamorada FL
    Update...

    Generators have to be removed for the welder to do his thing. Port generator has been moved and old shaft log has been cut out. New port log is going in tomorrow. Then, reinstall the port generator and pull/move the starboard generator and repeat.

    Attached Files:

  8. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    5,478
    Location:
    Miami, FL
    Hey at least you have plenty of room down there to move the genies around!!

    The amount of things this surveyor missed is incredible... When I Checked the stuffing boxes and discovered the busted clamps and bulging hoses Ii just couldn't believe my eyes, having read the survey before hand.

    Glad the welder got started Brian!
  9. Bamboo

    Bamboo Senior Member

    Joined:
    Dec 19, 2008
    Messages:
    935
    Location:
    Palm Beach, FL
    I've utilized Ocean Alloys/SS several times and they have also earned my recommendation. Talk with Randy.




    Moderator please remove if not allowed; thanks.
  10. Chevelle

    Chevelle New Member

    Joined:
    Jun 27, 2006
    Messages:
    42
    Location:
    West Palm Beach
    Just went through this on an 1988 Broward, looked the same on the outside. On the inside the log had corroded so badly that it broke the fiberglass cutlass bearing and squeezed it into a heart shape! We ended up cutting 6' of the logs on the end. Nobody involved could believe the shafts even turned! Boat jumps like a sportfish now when you drop it in gear and fuel burn was cut buy 40%!
  11. Scallywag

    Scallywag Member

    Joined:
    Apr 25, 2012
    Messages:
    67
    Location:
    Islamorada FL
    Wow! Amazing those props even turned with that kind of damage! Glad you got everything resolved thought. Were there bronze set screws in the cutlass bearings by any chance? Any clue what caused your corrosion?

    I'm having an epoxy barrier coat put down under the stuffing boxes and in the shaft pump well to address some of the pitting that is occurring. Did you run into any similar issues with your Broward?

    The welder finished the port side today. Moving on to cutting out the starboard side tomorrow. Finally, coming along nicely!

    Absolutely! I'm thinking I might put in a bowling alley down there right between the mains. :D

    Attached Files:

  12. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    12,773
    Location:
    Fort Lauderdale
    Several of the Browards I ran over the years had a good amount of pitting from where the stuffing box dripped. Most of them were changed to dripless stuffing boxes to aleviate that.
  13. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    8,763
    Location:
    Satsuma, FL
    I don't want to rain on anything here, but I have some comments on that last top picture; Maybe the picture is just not showing it correctly but it does NOT look like a lot of weld penetration into the shaft tube. Also, the tube looks short forward.
    Again, it could just be the picture,
  14. dsharp

    dsharp Senior Member

    Joined:
    Aug 23, 2009
    Messages:
    240
    Location:
    lake jackson, tx
    You're being very generous. I'm sorry but, those welds look awful.
  15. Scallywag

    Scallywag Member

    Joined:
    Apr 25, 2012
    Messages:
    67
    Location:
    Islamorada FL
    Rain away! The only time to get things right is right now. I'm not sure I follow you on the "tube looks short forward" part though. Are you talking about the very top picture of my last post?
  16. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    12,773
    Location:
    Fort Lauderdale
    I agree.
  17. Scallywag

    Scallywag Member

    Joined:
    Apr 25, 2012
    Messages:
    67
    Location:
    Islamorada FL
    A few more photos. For reference, the shaft log tube is approx 5 inches in diameter.

    Attached Files:

  18. wdrzal

    wdrzal Senior Member

    Joined:
    Feb 6, 2006
    Messages:
    402
    Location:
    Baltimore
    Those logs look like they were welded without first having the oxidation cleaned/removed............. And yes those are awfull looking welds, too cold ,no penatration. They should be ground out and redone. The blackness around the welds to me suggest maybe a mig with flux core wire might have been used ????? Thats far ,far away from a quality weld job.You can't magnaflux aluminium but you can dye test and check for cracks/voids under UV light.

    Either a mig with 100% argon shielding gas or a tig welder should should have been used.
  19. Bill106

    Bill106 Senior Member

    Joined:
    Jan 9, 2010
    Messages:
    389
    Location:
    Beaufort NC
    I have to agree, those welds are atrocious and need to be ground out and completely redone. This is what the ones looked like on that Burger project I referred to, not shaft tubes but this is what they should look like..

    Attached Files:

  20. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    8,763
    Location:
    Satsuma, FL
    Tube length comment

    If the interior shaft tube ends are to short, there will not be enough tube to attach a log hose with good clamping. I would like to see plenty of room for at least 2 clamps, maybe 3. And those clamps not sitting in bilge goo.
    It looks like you have allot of room in the picture but again, it's a picture and I may not see the whole setup.