Spacer for the outboard motor: protection of the transom and reduction of vibration

Any experienced boater knows that even a small boat-engine It can make a quiet walk a test for the nervous system if the mounting is not perfect. The tranny of the boat, especially made of plywood or thin aluminum, is constantly subjected to tremendous stress during the operation of the engine. strutting - a device that is often underestimated by beginners, but which is an indispensable element of the competent configuration of the boat.

The main function of this element is to rigidly fix the lower unit relative to the transom, which eliminates unwanted fluctuations and "cruising" of the engine in the rods. Many owners of PVC boats faced a situation where after an hour of stroke on the planing found that screw It lost some of its efficiency, and it shifted a few degrees to the side, which is a direct result of not having the extra thrust that the propeller's jet-wheel takes on.

In addition, ignoring the strut installation can lead to more serious consequences, such as cracks in the lower unit or even breakage of the translatum at the place of attachment of the rods. load on transom during planing may exceed 150 kgWhat are the types of struts and how to make a reliable stop yourself, using available materials and tools.

Principle of operation and purpose of spacer

To understand the importance of this element, we need to look at the physics of how the outboard motor works, and when the screw rotates, it not only pushes the boat forward, but it also creates a jet torque that tends to turn the entire engine around the vertical axis. If the motor is only attached to the rods, this moment is transmitted to the translucent, causing it to bend inwards, and the spacer creates a rigid triangle of forces, resting one end at the lower unit and the other at the tray or board.

The second important aspect is vibration: Internal combustion engines, especially two-stroke engines, vibrate when operating, and without rigid fixation, these vibrations are transmitted to the boat hull, causing resonance that tires passengers and can shatter fasteners. Spreadouts It can dampen these fluctuations, making the course smoother and more predictable, especially for boats with inflatable sides, where the rigidity of the structure is lower than that of metal counterparts.

Also worth mentioning is safety: If you hit an underwater obstacle or brake sharply ("beak"), the motor experiences an inertial jerk forward. If the rods are weakened or the translucent flexes, there is a risk that the engine will break off the mount and fall into the water.

• 🛡️ Reduces the risk of transom damage from constant pressure of strubcins.
• 📉 It extinguishes the vibration transmitted to the hull of the boat and the hands of the helmsman.
• ⚓ Prevents the displacement of the motor in the sides during maneuvers and on the wave.
• 🔧 Increases the life of the lower unit and gearbox due to the absence of distortions.

So, strutting is not just a fashion or a perfectionist, but a necessary measure to extend the life of both the boat and the motor, a simple element that dramatically changes the behavior of the vessel on the water.

Materials and types of structures

The choice of material for making or buying a strut depends on the type of boat you have and the power of the engine installed. Lightweight inflatable boats with engines up to 5 hp are often used simple wooden bars, sheathed with rubber. However, for more serious loads, materials with high compressive strength and bending, such as: stainless steel or aviation.

Structurally, the struts are divided into several types, the most common being telescopic clamps, which allow you to adjust the length depending on the engine's departure. These models are often equipped with a threaded connection or a spring-loaded locking mechanism. The second type is fixed arcs, which are attached to the transom with bolts and have a fixed length. They are more reliable, but require more complex installation.

Particular attention should be paid to contact areas. Places where the struts touch the lower unit and the transom should be equipped with soft but elastic gaskets, usually using rubber or high-density polyurethane, this is necessary so that the metal stop does not damage the paint coating of the motor or the structure of the transom when vibrating strongly.

Type of material	Advantages	Deficiencies	Application
Stainless steel	Maximum strength, durability	High weight, price	Motors from 15 hp, metal boats
Aluminum alloy	Lightness, corrosion resistance	Less rigidity than steel	PVC boats, engines up to 20 hp
Hardwoods	Cheap, easy to manufacture	It requires treatment, is afraid of water.	Motors up to 5-8 hp, temporary solutions
Plastic (capprolon)	It's not rusting, easy.	It might crack on impact.	Auxiliary stops, low power

When choosing a finished product or material for homemade products, it is important to consider the safety margin. If your engine weighs 30 kg, the strut should withstand a dynamic load of at least 2-3 times more, given the jerks on the wave.

Why can’t you use conventional construction steel?

Ordinary uncoated black steel will quickly rust in salt water. Even high-quality painting will not save, because in the places of friction and fastening the paint will be erased. Better use AISI 304 stainless steel or anodized aluminum.

Step-by-step instructions: manufacturing yourself

Making your own struts is a great way to save money and get a product that fits your boat configuration perfectly. To work, we'll need a stainless steel or 20-30mm aluminum profile pipe, two support pads and fasteners. The process starts with precise measurements of the distance from the lower unit to the transom thrust point.

First, you have to make or pick up the finished support cups, and they have to be concave, which is the same geometry as the lower unit, so that the contact area is maximum, and you have to weld or screw the hub in the center of the support, and you have to adjust the angle of inclination, because the lower unit can be tilted when you're working in shallow water.

The emphasis is telescopic, you take a larger pipe that you put on the main one, and you lock it with a bolt or a threaded clip, and you change the length of the strut if you're going to change the motors or use different boats, and all the threaded connections need to be protected from water with lubrication, for example. LIQUID MOLY Or analogues.

The final step is to install soft pads, cut the 5-8mm thick sheet rubber pads into the shape of the support pads, glue them to moisture-resistant glue, or bolt them so they don't slip in the water, and the finished structure is recommended to be tested on shore, applying a force to the motor and checking if the system is cruising.

Nuances of installation on PVC and RIB boats

The strutting of PVC boats has its own elasticity features. Unlike the rigid transom of a metal boat, the inflatable transom can walk. So the strutting point should be on the rigid insert (transe plate), not on the cylinders. The pressure on the soft side will cause deformation and loss of leakage.

For RIBs (boats with hard bottom and inflatable sides), the situation is similar, but it is important not to damage the fiberglass or aluminum cockpit. When drilling holes for fixing stationary stops, be sure to use a sealant for PVC boats, for example, TEK-NIK or 922to prevent the penetration of moisture into the layers of the material.

If you use a removable spacer, make sure it doesn’t block access to the drain valve or other important elements, and it’s also worth checking if the stress prevents you from opening the rundooks or accessing the battery if it’s in the nose.

⚠️ Warning: When installing the stop, make sure it does not touch the lower unit in the area of the lower unit pipe where the exhaust passes. Heating the metal can melt rubber elements or damage the paint.

It's also important to consider the angle of the trim, and if you walk around with the rear trim often, the point of application of the force on the transom shifts, and the strut must be sufficiently slid or versatile to work efficiently in all modes.

Comparison: factory models vs Homemade

The market offers many ready-made solutions from manufacturers such as Flagman, Burlaki Factory products usually have a well-designed, high-quality edge processing and warranty, but their price can be comparable to the cost of an inexpensive engine, which is a significant factor for many.

Homemades, in turn, allow you to realize any engineering fantasies. You can put the emphasis on folding so that it takes up the minimum space during transportation, or integrate additional elements into it, for example, the holder for the sonar sensor, but here you are responsible for the strength of the welds and the reliability of the structure.

Aesthetically, factory products look more neat, often powdered and anodized. Homemade designs may look rough, but when made from polished stainless steel, they can look even better than factory counterparts.

• 💰 Price: homemade is 3-5 times cheaper than a branded analogue.
• ⚙️ Functional: it is easier to make changes to specific needs.
• 🏭 Quality: Factory quality control is usually higher than home conditions.
• 🛠️ Repair: It is easier to repair your design in the field.

The choice between buying and manufacturing depends on your metal skills and the availability of free time. If you can hold a welding machine in your hands, it will take one evening to make it.

Maintenance and care

Like any element in contact with water, the strut requires regular maintenance. After each trip, especially on salt water, the structure must be rinsed with fresh water. The salt, drying on the metal, creates an aggressive environment that promotes corrosion, even on stainless steel.

Once a season, it is recommended to check the condition of rubber linings. If they crack or lose elasticity, they should be replaced. Hard rubber will stop quenching vibration and will begin to work as an abrasive, rubbing the coating of lower unit. Also check the reliability of fixing threaded joints - the vibration of the nuts can unscrew.

If the strut has movable telescopic parts, they should be periodically lubricated with silicone lubrication, which will prevent jamming of the mechanisms and facilitate the adjustment of the length. Do not use solidol or litol, as they are washed out with water and collect sand.

⚠️ Warning: Do not keep a boat with a spacer installed if it is in a compressed state under load for a long time (between seasons), this can lead to "tiredness" of the metal or deformation of rubber elements.

Timely care will avoid unpleasant surprises in the middle of the fishing season and will prolong the life of your equipment.

Frequently Asked Questions (FAQ)

Can I use a wooden bar instead of a metal pipe?

Yes, for motors up to 5-6 hp, you can use a block of hardwood (oak, larch) thoroughly soaked in olive or oil. However, wood has the ability to absorb moisture and swell, which can change its size. For more powerful motors, wood is not recommended because of the risk of breakage.

Do I need a spacer for an electric motor?

Electric motors tend to be lighter and operate at lower rpms, creating less vibration. However, the propeller's jet torque doesn't go away. For light electric motors (up to 30 lbs of traction), strutting is often unnecessary, but for high-power models (50+ lbs), the stop is desirable to preserve the geometry of the transom.

How do I know if my boat needs a booster?

If you hear a knock in the transom area, feel a strong vibration in the legs, or notice that the motor spontaneously changes the angle of rotation (sniffles), then the rigidity of the attachment is not enough, and the sign is the appearance of cracks around the fastening bolts of the transom.

Does the engine control interfere with the engine?

A properly installed telescopic spacer does not prevent the motor from turning left-right, because it is attached to the lower unit below the turning point or has a hinge connection, it limits only the undesirable tilt of the lower unit backwards, but not rotation around the vertical axis.

Where is the best place to put the lower part of the thrust on the transom?

The best place is on a hard transom plate, as close as possible to the line of action of the motor, but below the waterline, so as not to create excessive water resistance, it is important not to disturb the tightness of the inflatable elements if the PVC boat.