Hydraulic Flush – When, Why and How

Every system on a mega yacht is important to the overall comfort and safety of the vessel and vessel’s using hydraulics are no exception. So how often should a hydraulic system, like those used for the steering, stabilizers, bow thrusters or windlass operations be flushed? To be on the safe side, a sample of the hydraulic fluids should be tested every six to 12 months or whenever the system is opened and potentially exposed to outside contaminants, you suspect that water may have infiltrated the tank or metal particles are found in the oil.

There are three methods for flushing a hydraulic system. The first is a simple drain, filter, fill approach referred to in our shop as a DFF. This type of flush is actual more of an “oil change” and is typically recommended for routine maintenance.  It is not appropriate where a more serious condition such as water, metal particles or other contaminants are found in the oil. In this scenario, we would drain the hydraulic tank, change out the filters and refill the tank with hydraulic fluid. Pretty straight forward.

The second method, known as a double oil and filter change, requires us to drain the hydraulic tank and fill with fresh oil that will be circulated using on-board system pumps. This method would be suggested under a few conditions; many years since last oil change, requirement to change oil types, minor discoloration of oil, etc.  This method involves an initial oil drain from the tank and low points in the system and filter change which can expel a large percentage of contaminants and degraded fluid. We would then fill the tank to the minimum level allowable to still safely work and circulate the oil until operating temperature is achieved. The oil is drained again and the filters changed for a second time before re-filling the hydraulic tank with fluid. For best results, the system should be drained as thoroughly as possible including the tank and manually cleaned.

The last option is more time consuming and costly and is used when there is known contamination of water or metal particles. This method often uses special high pressure pumps or power flushing rigs. Some of these pumps or rigs have directional valves that enable flushing direction to be changed which can assist in dislodging contaminants from dead spaces throughout the system. As in previous methods, the first step is to drain all old hydraulic fluid from the system and refill with a low viscosity fluid that will be circulated at high velocities to create turbulent flow conditions that equate to a Reynolds number of more than 2,000. This process would be repeated as needed until there is no longer any contaminants present in the filters or fluid. We would also remove, inspect and when necessary replace any hoses, cylinders and valves that are damaged.

Just like changing the oil in your car or any other mechanical device, hydraulic systems on your yacht need care and attention to keep them performing in peak conditions for years to come.

Repairing a leaking Heat Exchanger in a Bow Thruster HPU

We were recently contracted to inspect a leaking heat exchanger on a 130 foot Westport yacht docked at a local marina. The heat exchanger was part of the hydraulic power unit (HPU) for the ship’s bow thruster system.  The HPU consists mainly of a motor, a reservoir tank and a hydraulic pump. These units can generate a tremendous amount of power to drive most any kind of hydraulic ram or motor. They can also generate high temperatures. Most heat exchangers used in the marine industry are water cooled and use a water control valve to regulate the flow of water though the exchanger to keep the hydraulic fluid temperature between 64 and 68 degrees C (147 and 155 degrees F). It is important to make sure the adjustments for the water control valve are set properly to avoid rapid overheating.

This particular model was a shell and tube design.  As its name implies, this type of heat exchanger consists of a shell (a large pressure vessel) with a bundle of tubes inside it. One fluid runs through the tubes, in this case hydraulic oil, and another fluid, water, flows over the tubes (through the shell) to transfer heat between the two fluids. The set of tubes is called a tube bundle and may be composed of several types of tubes.

Upon inspection, we found that the fittings in the heat exchanger were not properly seated and the sealant used was not sufficient for the job. In order to remedy the problem, we needed to remove the heat exchanger from the HPU and send it out for servicing. In order to do this, we had to disconnect the hard pipe Stauff clamps above the heat exchanger in order to spread the pipes apart to remove the heat exchanger from the bilge. We also disconnected and installed caps and plugs in the hoses connected to the heat exchanger. We resealed the adapters and fitting upon re-installation, connected the hydraulic hoses, installed Stauff clamp supports and tested the unit for leaks.

The heat exchanger is back in operation and helping to ensure that the hydraulic bow thrusters are doing their job helping to maneuver this yacht in tight places.


Overhauling BCS trim tabs on an 85 foot Ferretti

BCS Trim Tab

Trim tabs are an essential component for any yacht. They improve performance, helping to increase speed, reduce pounding and on smaller boats offset prop torque. They help the vessel run more efficiently, reducing fuel consumption and engine laboring and eliminate “squatting.” But more importantly, they increase safety by improving visibility and handling along with reducing wake size and hull stress.

However, years of use and prolonged exposure to salt water can take a toll on their ability to function properly as was the case with an 85’ Ferretti that was hauled at Lauderdale Marine Center.

That is when our hydraulics team was called in to work on the BCS hydraulic trim tabs. Upon close inspection, we found that two of the four trim tab cylinders were corroded beyond repair and needed to be replaced. Because of manufacturer’s long lead time, we decided that we would machine new rods, barrels and re-build the cylinders in-house, using our machine shop, Straight Line Marine.

Corrosion in Barrel

The corrosion we found on the inside of the barrel was caused by salt water intrusion as a result of failed seals. Once the components were machined, we were ready to assemble the new hydraulic trim tab cylinders and re-install in the yacht. Unlike common trim tab cylinders, the BCS model does not use hydraulic hoses to distribute the hydraulic fluid to operate the trim tabs. The fluid is dispersed through a small pin hole in the transom bracket assembly. A clever design that eliminates hose failure external to the transom. However this creates a tricky install.

Pin Hole

The pin has multiple O-rings and requires a special touch to avoid pinching during installation. Great care must be taken in the removal of the old hydraulic trim tab cylinders and the re-installation of the new ones. Damage to the assembly as a result of scratching or scoring the unit would cause them to leak and render the trim tab cylinders useless.

We see these types of nuisances all the time. It takes a team of highly experienced hydraulics technicians to properly diagnosis the problems and take the appropriate actions to correct them.

Giving an Old Hydraulic Royal Boarding Ladder a “Face Lift”

From time to time, we see some pretty old yachts come into Lauderdale Marine Center as was the case with a 30+ year old Feadship. This old gal was in need of some work to bring her back to her glory days. We were hired to give her hydraulic royal boarding ladder a “face lift.”  A hydraulic royal boarding ladder is side mounted typically at mid-ship that retracts using hydraulic folding mechanisms when not in use, leaving your deck free of obstacles.

The job included stripping the boarding ladder for a new paint job, replacing the hydraulic hoses and hydraulic cylinders and installing new hardware right down to the nuts and bolts.

The royal boarding ladder now looks brand new with no traces of 30-odd years of use.

Working on a 26T Crane takes special tools, equipment, coordination and expert experience

The captain of a 215’ Expedition recently contracted our hydraulics team at High Seas Hydraulics to work on the vessel’s crane. This particular yacht is a shadow boat hired out to “shadow” luxury yachts ferrying extra crews and other “toys” the luxury yacht owners or guest may need on their extended voyages. Those toys can range from large tenders to cars to even a helicopter.

The two luffing cylinders on the crane were leaking hydraulic fluids at the seals and needed resealing before the vessel went out to sea again. The catch on this job was the size of the crane, the weight of the cylinders and the timeline to fix. We had just one week to pull, diagnose, fix and re-install the luffing cylinders on this 26 ton crane, the largest crane we have worked on at High Seas Hydraulics. Each luffing cylinder weighs over a ton and needs special equipment to handle.

Coordination was key to ensure this job went smoothly. We first had to rent scaffolding that needed to be erected on the aft deck in order for our hydraulic technicians to reach and secure the cylinders for removal from the boat. We then rented a boom truck with a 73 foot reach from a local business to remove the luffing cylinders from the yacht and place on our sister company, Straight Line Marine’s flatbed truck for transportation back to the shop. Having a flatbed truck as part of our fleet comes in handy for these types of jobs as well as moving large shafts from mega yachts.

Once back in the shop, we inspected the luffing cylinders and sent them out to be resealed. The company that we contracted to reseal the luffing cylinders was unable to pressure test the luffing cylinders due to equipment problems so they were returned to High Seas Hydraulics. Fortunately, we have the proper equipment and experienced technicians to perform the testing in house for these cylinders that required 2,500 pounds of pressure.

Communications is key

Upon completion of the service work and testing, we returned the luffing cylinders to the yacht using our flatbed, brought the rental boom truck back and re-erected the scaffolding. Here is where the real precision work comes into play. While the boom truck does the heavy lifting, our hydraulic technicians guide the cylinders into place using safety line, straps and chain come-along ratchets. Communications with the crane operator is crucial and is most often done with hand signals.

We first secured the lower end of the cylinders into the crane and pinned them into place while they were still attached to the boom truck crane. Installing the pin on a crane of this size takes balance and a little brute force! Once in place, we released the straps from the boom truck crane and using straps and the chain come-along ratchets, raised the luffing cylinders into place for securing the top to the crane. We then reattached the hydraulic hoses to the yacht’s crane so we could use the boat’s hydraulic power to extend the luffing cylinders for the final pin installation. While this work takes experience and knowledge of the process, performing the task while standing on scaffolding more than 10 feet of the deck adds to the complexity.

Once the luffing cylinders were firmly and securely in place, we re-installed the rest of the hydraulic hoses and tested the crane to ensure that it was working properly for the demanding tasks it undertakes while at sea.

This was a big job with a tight timeline that we were able to push through so the captain could meet his charter schedule. This shadow boat is ready to set sail with those “little extras” that help to make memorable adventures.

Removing Deck Cranes off of a 121’ Heesen

A 1987 121’ Heesen Yacht was recently hauled at Lauderdale Marine Center and both High Seas Yacht Service and High Seas Hydraulics were called upon to bring some life back into this old girl. After 30 years of cruising the oceans, she was in need of some major overhauls on a number of her systems.

One was to remove a couple of old deck cranes from her upper deck which had long since stopped working. Typically when we remove deck cranes for refurbishing, we carefully dismantle the various components to diagnosis the problem and once corrected reinstall the units back in the boat. In this situation, it was deemed that the deck cranes would probably be replaced with new units so we took a more expeditious approach to the removal.

Securing Crane

Our hydraulics team, working closely with the Lauderdale Marine Center ship yard crane operator, methodically attached a number of straps to the units to stabilize them as they worked to release the bolts from the plates that secured the deck cranes to the boat. We are fortunate to have an outstanding crane operator – Angel – that is slow and patient.  Constant and clear communications with the ship yard crane operator is crucial to this task and can only come with years of experience working on these types of jobs When you think about the loads these deck cranes are responsible for while hoisting tenders or other equipment more than 30 feet in the air, removing the bolts was no easy task and had to be done with precision to keep the unit from shifting and possibly damaging the yacht.

Once the bolts were close to releasing the crane from the deck, our crew needed to quickly re-adjust the straps in order to control the unit as it was lifted into the air. Cranes have a very uneven weight distribution and weigh several hundred pounds so without the proper balance applied by the straps and chain come-along, they could twist or slip potentially hitting the deck or the side of the yacht while being lowered to the ground.

This type of work takes a lot of experience, knowledge of the units and patience to do it right and to do it safely for both the crew and the vessel.

When Small Problems Become Big Issues

When a 58’ Kady Krogen trawler recently hauled out at Lauderdale Marine Center, our running gear company, High Seas Yacht Service was hired to pull the props and shafts for a routine cutlass bearing and seal service. High Seas Hydraulics was also hired to do routine service on the ABT Trac hydraulic stabilizer systems.

Damaged threads on shaft

Once we dropped the stabilizer fin in order to replace the lower shaft seals, we found the threaded stud on the bottom of one of the shafts was damaged and had signs of thread damage and galling.  This was most likely from a stainless steel nut on stainless steel threads that was installed and removed without the proper never seize.  This compromised the re-installation of the stabilizer fin nut so we recommended removing the shaft to repair it in our machine shop, Straight Line Marine. Once in the machine shop, we found that the stabilizer shaft was bent 0.080” which is significant for a stabilizer shaft. When we started the straightening process, which involves applying hydraulic force on the high point of the shaft the stabilizer cracked in two.  That was a first – never had that happen before.  Under examination of the broken ends it is evident that a crack in the shaft had worked its way to 20% through – we just finished off the job.

Cracked shaft


This particular vessel is under new ownership so there is limited history as it relates to past problems and repairs. Obviously, this stabilizer was badly damaged at some point in the past. In all likelihood, the boat probably hit something or experienced a hard grounding which lead to a crack in the stabilizer shaft. Over time, these cracks tend to creep and grow.

We were able to source a new stabilizer shaft from the manufacturer and complete the overhaul on the hydraulic stabilizer system.

We have never experienced a stabilizer shaft cracking in two before in our machine shop, but it just goes to show that a small thing such as damaged threads can be a warning sign of bigger issues.

Performing a Major Overhaul on NAIAD Stabilizer System

Continuing the work on the 135’ Broward, we have moved on to work on the NAIAD stabilizer system. While NAIAD does not specify an exact interval for performing a major overhaul, it does recommend replacing the lower seals every three years or 4,000 operating hours. Interim service and maintenance should be performed annually but a major overhaul is highly recommended anytime you find water in the grease beyond the outer shaft seals or signs of grease oozing from the inner seals around the shaft.  Once salt water compromises the grease the bearings will start to deteriorate and the grease needs to be replaced

For this project the customer wanted the major overhaul which encompasses removing the fins from the boat, removing the top plate, tiller arm, hoses and shaft. Taking apart the cylinders, inspecting the potentiometer. Basically, the entire system is removed and stripped down.

The upper and roller bearings are installed on the shaft. So when the shaft is removed the roller bearings stay with it. The roller bearings are cut off the shaft in our machine shop, Straight Line Marine. Next the shaft is polished in a lathe and inspected for corrosion or scarring in the lip seal area   . If we do find corrosion, we will clad the corroded area. In this case, we did find corrosion. Once the work on the shaft was complete, we installed new bearings using heat to avoid scoring the shaft.

Cladding shaft

Once the vessel is launched, we will bring up the electronic side of the system and test or reset the potentiometers. It is usually not until this late stage in the project that we can determine if the potentiometers need to be replaced. Once we completed all the steps for this major overhaul, we reassembled the unit and re-installed it back in the boat. The hydraulic stabilizer system on this Broward yacht is good as new and ready to take the captain and crew on more adventures and smooth sailing.

For more information on performing major overhauls on hydraulic stabilizer systems, check out our technical article on the process.

Manually Raising a Hydraulic Swim Platform After a Failure


Platform submerged

Our hydraulics team at High Seas Hydraulics was recently called out to help the captain of a 95 foot Technema yacht docked behind a private residence with a problem with the ship’s hydraulic swim platform. The hydraulic swim platform was stuck in the down position below the water line and leaking hydraulic fluids into the water. Before the team started to work on raising and securing the hydraulic swim platform, they needed to contain the leaking hydraulic fluids.  Upon arriving on site, they quickly deployed a special containment boom and secured it to the transom of the boat. They also used absorbent pads to filter the hydraulic fluids that had already leaked into the water. Once the boom was secured, the work could commence to start to raise the hydraulic swim platform so that the yacht could be moved to a yard for repair.

For this job, we hired professional divers to deploy air bags under the platform to raise it enough to use a pulley and ratchet system to hoist the hydraulic swim platform back onto the the locking hooks on the transom of the boat where it would normally rest. We first needed to

Divers with air bags

secure the hydraulic swim platform with straps that we could attach to the ratchet system in order to help raise it after the air bags
were inflated.

Once the hydraulic swim platform was raised a couple of inches with the air bags, we disconnected the hydraulic hoses on the inboard side of the unit to alleviate back pressure to help stem the flow of any additional hydraulic fluid into the water.  Relieving the back pressure also allowed the hydraulic cylinders to move more freely in order to raise the hydraulic swim platform. After the hydraulic swim platform was aligned and snug to the boat, it was further secured with straps and the locking hooks for its journey to the boat yard.

Platform secured to transom

One of the primary reasons for a failure of this type is wear and tear and prolonged exposure to sea water of the hydraulic cylinders and hoses that are located on the outboard side of the yacht. To avoid this type of problem, it is a good idea to inspect the hydraulic cylinders and hoses every time the boat is hauled and refurbish or replace them at the first sign of wear on the components. Spending a little time and money to keep the parts of the hydraulic swim platform that are exposed to sea water in top operating condition can ultimately save you big money in the future, not to mention potential fines and citations should your vessel leak hydraulic fluids into the waterways. While this type of failure is not prevalent, the day after we performed this job we were called out to perform the exact same thing on a 64 foot Azimut.

Refurbishing a Hydraulic Steering System on a 135 foot Broward Yacht


As part of the refit of the 135 foot Broward, the new owner wanted a complete overhaul done on the hydraulic steering system. We started by removing the steering cylinders for tear down and reseal before sending them out to be painted.

We next disassembled and removed the hydraulic power unit (HPU). The HPU consists mainly of a pair of motors, a reservoir tank and a hydraulic pump. These units can generate a tremendous amount of power to drive most any kind of hydraulic ram. Hydraulic Power Units are based on Pascal’s law of physics, drawing their power from ratios of area and pressure. In this case, the HPU takes the commands from the helm to push the hydraulic rods in the right direction to steer the yacht. A failure of the hydraulic steering system at sea or just about anywhere could prove to be catastrophic.

Once the unit was out of the boat, we cleaned the tank, check the values, sent the electronic motors out for testing and tested all of the pumps to ensure they were in good working order. We also made all new hoses for the unit in our hydraulics shop.

Once all parts were examined for quality control purposes, we reassemble the HPU and installed it back in the boat. A completely refurbished hydraulic steering system to like-new specifications will help to provide peace of mind that this yacht and her crew can safely navigate through any waters.