The Triton

Engine Room

Think of hull, running gear, mounts in spring yard time


All too often, the yachting industry can be too focused on keeping up appearances. That’s not to say that some of the more cosmetic maintenance of a yacht isn’t important, because it is. But the old adage – it’s what’s on the inside that counts –  definitely carries weight.

With the spring yard season hovering, here are a few important checks that can be done for a modest investment that will spot any conditions before they become issues, and provide peace of mind.

  1. Even if vibration or noise is not present, a pre-haul vibration analysis is always a good idea. Think of this as an EKG for a vessel. It can spot any issues, such as misalignment, propeller problems, engine misfire, exhaust system deficiencies, and deteriorated mounts and worn bearings. It can also pinpoint crucial mechanical elements that need attention, and forecast what problems are likely to appear, including what should be monitored closely in the future.
  2. During a haul-out, your project manager will be a vital point of contact to maintain the efficiency of the yard period and keep you on schedule. Maintaining good communication and ensuring they have thorough information, such as drawings, a work list, and technical documents will help ensure that the yard can properly accommodate you with such things as the proper straps and blocking. As menial as this may sound, using the correct straps and blocking will prevent damage to the running gear.
  3. Another service item that should always be done is a hull target. This establishes the shape of the hull in the water, and then, once blocked, the shape of the hull on land. Typically, the yard will run a piano wire along the port and starboard sides or the main deck with the wire fixed on both ends. Another more advanced and technical option uses a geometric laser system, which features a 3D rotating laser. The laser receiver records specific data point measurements of the structure of the vessel while in the water. The readings will then be collected again, once the boat is hauled and on blocks, to allow for any variances if it changed shape out of water.

Unfortunately, the laser isn’t always a viable option, especially if deck space is limited. But even when performed with wire, a hull target is extremely important should any misalignment be present or if an alignment issue appears.

  1. Once hauled, shaft seals and their cooling supply lines should be checked. Seals need to be cooled by water for proper function, so if the cooling lines are damaged or showing wear, they should be replaced. The seals need to be examined to see if they just need service or be fully replaced. Determining what parts are needed early on in the haul out will usually allow for time to procure them, should spares not already be on hand.
  2. The yard or the subcontractor working on your running gear should perform a rudder pull test to check for bearing play. The rudders should be given a good shake to check for excessive play in the bearings or rudder hardware. The propellers and shafts should be removed so they can be cleaned and inspected to determine if they need to be reconditioned and/or straightened.
  3. Some other checks that are relatively easy but extremely important involve the engine mounts and bearings. Reviewing the vessel’s records and knowing when the mounts were last changed, how many running hours they have, and their make and model are all helpful.

An inspection of the mounts should be performed, mount deflection measurements taken, and a report provided, detailing their condition. Bearing information should also be researched to find out age, make and type. The service technician assessing their condition will record their clearances and can determine if there’s any problems, such as the rubber being separated from the sleeve.

  1. With the running gear pulled, an optical alignment check can be done to see where the alignment is and determine what corrections, if any, need to be made.
  2. Once everything is put back together and the vessel is launched, “burp” the seals to vent them and make sure all of the air has escaped the stern tube and water is at the seals and forward bearing, providing proper lubrication. This can be done by temporarily disconnecting the supply line closest to the top. Attempting to burp the seals at their main sealing points may allow dirt to slide into the seal elements and cause leaking.
  3. After settling back in the water for 24 hours, a final laser check can record the alignment.

If all is good to go, the yard period can be wrapped up with a post works vibration analysis that will serve as a comparative to the vessel’s pre-haul condition, and verify you did your job thoroughly and correctly.

Rich Merhige is the owner of Advanced Mechanical Enterprises and Advanced Maintenance Engineering in Ft. Lauderdale, which specializes in rotating and reciprocating machinery. This column is co-written by Teresa Drugatz, marketing manager at AME. Contact them through or +1 954-764-2678. Comments on this column are welcome at

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