Click for Furuno Click for Burger Click for MotorCheck Click for Cross Click for JetForums

Mystery - Periodic "slippage" at cruise

Discussion in 'Viking Yacht' started by incoming, Sep 2, 2022.

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

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    111
    Location:
    Cocoa Beach, FL
    I just had my stbd trim tab removed - it broke at the hinge and i wanted to be able to use the boat while i'm waiting ~90 days for a new one.

    On the way back to my marina from the haul out facility - every 15 minutes or so while running on plane, the boat would suddenly veer about 5 degrees to one side or the other - the way a car feels when when hitting a patch of ice. This also happened on autopilot - it took 5 sec or so for the autopilot to dapen it out and get back to running.

    I checked the aft bilge and found one of the nuts had come loose from the threaded rod connecting the two rudders. The rod itself was not loose though. I tightened the nut back up, but then had the issue happen a couple more times.

    Any idea what this could be? I was thinking maybe a bubble in the hydraulic steering - but would it have happened both on autopilot and manual steering if so? Could a rudder be slipping? is that a thing?

    Odd that it happened right after the haul out and trim tab removal - but i'm thinking coincidence.
  2. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    8,120
    Location:
    Miami, FL
    Air in the steering would result in sloppy steering not just for a few seconds at speed. Have you check the fluid level or looked for leaks?

    many change in RPM, synchronizer issue?
  3. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    111
    Location:
    Cocoa Beach, FL
    steering fluid level hasn't changed in a couple dozen hours of running

    i thought about maybe a synchronizer issue, because i did have the sync on. But, i did not hear a change in RPM or see the tachs flutter.
  4. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,649
    Location:
    Satsuma, FL
    Was the un-broken tab all the way up?
    Below the hull tabs? in pockets? or extended past the hull?
    I'm assuming your not stabilized.
    I'm assuming your not thru the hull exhaust before the props.
    With a lot of SWAG, I could see in my mind (past the cob-webs, dust and empty's), when the transom come down on a swell, even a little one, there is still some mis-matched lift on one side of the hull.
    If a hull pocket for the tabs, could that help the prop vent?

    These may be the only wet side ideas that I can think of,,, before 1700.
    DE74600B-1C8A-4D3F-B779-311C0222E0F5.jpg
  5. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    111
    Location:
    Cocoa Beach, FL
    The remaining operational tab was fully stowed (I thought of this too and checked after the first instance)

    No active stabilization, exhaust is in the transom.

    The tab actuator arms are slightly recessed into a pocket in the transom, but the tabs themselves are mounted flat on the hull. The net effect is that there is slightly less wetted surface on the side with the missing tab - maybe 20” x 1”-2” (pic attached)

    I suppose it’s possible that there is some sort of instability created by this, but it seems quite small in relation to the overall wetted surface.

    This was cruising on the Indian river (central fl icw) with winds less than 10 kts and no swell or chop - almost lake-like conditions

    Attached Files:

  6. motoryachtlover

    motoryachtlover Senior Member

    Joined:
    Jan 29, 2007
    Messages:
    645
    Location:
    smithfield, VA
    I am not a mechanic and defer to the other posters with more mechanical experience than me. But I think it is worth your time to look for black dust in and around your bell housing of the transmission. The symptom you describe is similiar to what I experienced before I had a torsional coupler let go. But what is not consistent with your situation is that mine would drop rpm and shudder. But Vikings of this vintage with ZF 350s were known for blowing torsional dampers or couplers. They have since come up with silicon dampers which supposedly give much longer service. Good luck.
  7. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,649
    Location:
    Satsuma, FL
    It looks like you have a nice keel also.
    myl hay have a thought. Or a point in a good direction;
    Get your clutches oil into a lab quickly.
    Inspect the bell housing vents carefully, if the vents are removable, open them up and inspect inside the housing if you can for plastic debris.
    Happen in Sync?
    What engines, clutches and synchronizer?

    I'll try to kill off some slow brain cells and get back to you later this weekend.


    Oh, do you use tabs to bring the bow down quicker?
    Do you continue to have your tabs down while you run? A little, A lot?
    I'm thinking the tabs are not an issue but double checking an other idea before passing on them completely.
  8. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    111
    Location:
    Cocoa Beach, FL
    I generally use the tabs to move the bow down slightly, netting me about 1-1.5 kts at cruise. I generally don't deploy them until i'm up on plane.

    Engines are 1200 hp mans. Synchronizer is a mechanical glendinning (don't know the model - circa 1998). Gears are BW165.

    Because you guys are asking about the trannies - i do have a gear oil leak on the port transmisssion. i originally thought it was the shaft cover over the bearing housing. But i've had that replaced and resealed. The last people i had out said they noticed the gear oil cooler, which is mounted above, is a non-OEM replacement and leaking onto the cover below. I'm waiting on a quote from them to have that replaced.

    So...knowing what you guys are thinking...is it possible i'm temporarily losing gear oil pressure? I don't see how the pressure would collapse like that and suddenly recover.

    Also - this happend three times in a 1 hour ride - and in none of the cases (even when i was paying close attention) did i see the tachs flutter or hear the engines "hiccup"

    The two things that seemed to be "amiss" are the missing trim tab and nut that was loose on the rudder connector rod. but it happend another time after i tightened that nut.
  9. LAM

    LAM New Member

    Joined:
    Nov 8, 2007
    Messages:
    7
    Location:
    MD
    Just curious if ever found the problem?
  10. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    111
    Location:
    Cocoa Beach, FL
    I’m 99% sure it was the missing trim tab on the stbd side creating an instability in lift at the back of the boat while on plane. Took 6 mo to get it replaced (thanks Bennett) - splashing the boat in about a week and will be able to verify.
  11. incoming

    incoming Member

    Joined:
    Jan 14, 2021
    Messages:
    111
    Location:
    Cocoa Beach, FL
    Verified - the problem was the missing trim tab all along. With both tabs installed again, the boat runs beautifully, autopilot holds course as it should, no weird squirrelyness