Prop, Shaft and Rudders on a 61' Marlow

The new owner and new Captain on a beautiful 61′ Marlow came into the yard.  The vessel had a major vibration that was most noticeable when driving from the lower wing station.

After removing props we went through our standard running gear inspection process – checking shaft run-outs, bearing clearance, seals and engine mounts.  The running gear all checked out within spec so no need to pull shafts and create a big bill.

The rudders were extremely loose with up to 0.125″ of play and slop in the tiller arm pins.  This was clearly a source of vibration with the prop wash rattling the rudders around.

Marlow’s were built using cutlass bearings as lower rudder bearings.  We believe that allows too much play and premature wear.  The lowers and uppers were replaced with Tides Marine UHMW bearings.  The machine shop re-bushed the tiller arms and made new pins for the tie-bar.  New Tides Lip seals and back together – all nice and tight.  We only traveled a hundred yards in the New River before the Captain declared the problem solved.  A month later he sent us the following update:

“Hi Chris,  Thought you should know that the boat is running better then the day we bought her, thank you. Less noise etc. And we can actually run over 1400rpm with out breaking plates. ”

Next time you have a vibration, try to listen closely to your rudders.  Don’t assume it is a shaft or alignment problem.  And make sure you use a contractor that will take the time to inspect before tearing apart.  We saved this owner a tremendous amount of money by recommending a “pass” on a full shaft job.

Centa Coupling Disassembled Exposing Roller Elements

Tis the Season for working on torsional couplings.  This particular unit came out of a 75′ Sunseeker with a ZF V-drive and Cardan shaft configuration.  Similar to the last post on Vulkan Couplers, this unit is attached to the flywheel and designed to take the various torsional loads that are transferred between the drive-line and engine.

Float aligning a cutlass bearing in a strut

In past posts we sea-trialed a 120′ Intermarine and observed a bad vibration with the vibration analysis expert and took a video of the obvious problem as seen on an aft cockpit table.

Stay tuned for an upcoming post that provides more insite on this topic.  The attached photo is credited to Professional Boatbuilder Magazine and I am working with them to publish past articles on the subject.  

In the meantime, feel free to comment on this picture – let the debate begin……again.

Shaft Damaged with Electrolysis

In a prior post “Electrolysis Destroys a Shaft” we cover a story about a 50′ sailboat that almost lost their Maxprop due to a severely damaged shaft.  They were very lucky to haul for routine bottom paint when they did – a few more months and the prop would be gone.

“The entry on shaft electrolysis caught my attention.  Electrolysis is a word the marine corrosion community frowns upon, primarily because it references a chemical reaction rather than carrion per se.  The photo of the damaged shaft is likely a result of stray current corrosion rarer than galvanic corrosion, which anodes would prevent.  No amount of anodic (zinc or otherwise) protection will contend with stray current corrosion for anything more than a short time.  Stray current corrosion results from DC current leaking into bilge water or via an un-bonded through hull.  It typically causes significant damage in a very short period of time, as opposed to galvanic corrosion, this is the kind that is mitigated by anodes, which occurs slowly.  Both are easily identified using a multi-meter, although not always easy to resolve. ”

Sincerely,

Steve D’Antonio

Steve D’Antonio Marine Consulting, Inc.

www.stevedmarineconsulting.com/

I will gladly take feedback anytime from a known expert and update the site in an effort to be accurate and educational.  Thanks Steve!

Shaft Damaged with Electrolysis

A simple prop change on a sailboat turned into a major surprise for the owner.   All of the zincs were gone by the time it was hauled into our yard.  The Maxprop had badly damaged prop blades due to electrolysis.  Once the prop was removed the Spurs cutters showed similar damage. 

Bent Strut in Machine Shop

Bent struts are obviously an alignment problem.  The only way to correctly fix a bent strut is to remove it from the vessel, straighten out the bend in the machine shop and reset it to the boat using the optical scope alignment process. 

This strut came out of a 109′ Hargrave.  Apparently she spent some time docked in a slip that did not have much water.  A few hours resting on the prop in very low tides put enough upward pressure on the strut to cause the permanent bend.

Some yards attempt to heat and bend props while still attached to the vessel.  This might work in an emergency to get you to a destination or final work yard.  This is never a good idea for a permanent fix.  You can’t get the bend back in the right place and getting an alignment within 0.010″ with sledge hammers does not work.

Once the strut was reinstalled, shaft straightened and overall alignment completed, a sea trial went perfectly.  Another customer with a smooth boat that is now part of our customer reference list.

Same Strut after a little machine shop work

Tides Lower Bearing and Seal Assembly

A past customer called with an emergency problem.  His 61′ Queenship was taking on water from the rudder seals and needed to be hauled and serviced right away.

The system was an old version Tides rudder bearing and seal Type “D” and the problem was four-fold. 

The old seals were worn. 

The upper bearing in the shelf had come loose and was allowing too much play in the rudder stock.

The lower bearings were out of specification allowing too much rudder stock movement.  Tides allows up to .025″ before replacement.

There were no spares on the rudder shaft to allow for temporary repairs.

Queenship 61' After Rudder Bearing Repair

After haul-out we dropped the rudders and inspected the bearings.  The upper shelf bearings were in tolerance and OK once re-secured in the proper aligned position.  The lower bearings required replacement since they were beyond the .025 wear specification from Tides Marine.  Replacement was relatively simple with the Tides Type D system.  The new bearing and seal assembly threads into the existing tube that is already glassed and bedded into the hull.

Final launch and check – dry bilges and solid rudders.

Too Much Torque on this Tide Seal Housing – Major Failure

Recently we had an 80′ Lazarra come out for basic bottom and propeller work.  A courtesy inspection of all running gear exposed a major problem for this new owner and crew.  The Tides Seals – Sure Seal (dripless) system was cracked completely through.   The outer ring and collar are solid pieces that should not show signs of cracks or splits.  Unfortunately, the repair requires removal of the coupler which is the first step to removing all of the running gear.

Classic '84 Palmer Johnson with a fresh alignment tune-up

This classic 1984, 84′ Palmer Johnson suffered from binding cutlass bearings.   This created vibrations and unusual engine loads.  Once hauled, the problem was apparent when it took full body weight leaning on the props to get the shafts to budge.  Once the shafts were removed, which was needed for cutlass bearing replacement anyway, the optical scope was set up on each side.  The problem was obvious, the bearings in both the intermediate and main struts were out of alignment – a lot.  One of the benefits of the optical scope is the ability to show the Captain and Engineer exactly what is wrong.

All four bearings were “float aligned” into the proper, permanent alignment positions.   The boat was assembled and launched right on schedule and sea trialed shortly after and headed for its annual 2,000 mile summer delivery.   Even before the launch and sea trial the results were apparent – you could now turn the propeller with a single hand.  With a good pull you could spin the prop a half turn – pretty nice for gear this size.

It is always great to hear from customers.  Three weeks after the work was complete, the PJ was back up North.  The Captain called to report the smoothest ride he has felt on the boat in 10 years.  In addition, there was a noticeable and substantial savings in fuel.  Stay tuned. as we might have some hard data to report in a future update.