Proper storage of an outboard motor is not just a matter of order in the garage, but a necessity that prolongs the life of an expensive unit. outboard motor stand It must be in a stable vertical position, preventing oil from leaking out of the gearbox and deforming the lower unit, errors in the calculation of the dimensions of the support structure can lead to the fall of heavy equipment, which can lead to injuries and financial losses.
Many aquatic motorists underestimate the importance of precise geometric parameters, relying on approximate measurements by eye. millimetre precision When making or choosing a rack, it ensures that the motor will not stagger during transportation or is idle. In this article, we will discuss in detail the standard and individual dimensions necessary to create a reliable support.
It should be borne in mind that the dimensions of the support directly depend on the engine power and the type of lower unit (long or short leg). Universal solutions here are almost non-existent, so understanding the principles of calculation. foot-stay And that's going to be a key skill for any boat owner, so let's get to the specific numbers and the technicalities.
Critical parameters for structural stability
When designing or selecting a rack, the support area is paramount. The more powerful the motor, the wider the base should be to avoid rollover by inertia or accidental push. For low-power models up to 5 hp, a 30-40 cm wide base is sufficient, whereas for engines over 50 hp, this parameter should be increased to 60-80 cm.
The height of the vertical pillar is the second most important parameter, which is often miscalculated. lower unit engine The ideal height is usually between 90 and 110 cm, but the exact value depends on the length of the diewood of the particular model. Yamaha, Mercury or Tohatsu.
An important aspect is the angle of tilt of the mounting pad. Many factory models are adjustable, but when self-manufactured, you need to lay the angle corresponding to the transom angle of your boat or boat, which allows you to store the motor in the same position in which it works, which reduces the load on the oil seals.
⚠️ Warning: Never use a base area of less than 25x25 cm for motors over 15 hp, as the center of gravity shifts upwards, making the structure unstable.
The fabrication material also dictates its size limits. If you use a profile pipe, the walls must be thick enough to withstand the weight without bending. For steel structures, the pipe cross section may be smaller than for aluminum counterparts where you need to. cross-section It's to keep it tough.
Standard sizes for engines of different power
There are some unspoken industry standards that accessories manufacturers adhere to, based on statistics on the size of dayswoods and the weight of engines of different classes, and understanding these standards will help you quickly navigate your assortment of stores or when ordering welders.
The two-stroke and four-stroke low-power (2-6 hp) engines are compact, do not require a massive base, as the weight of the unit rarely exceeds 25 kg. However, even lightweight models need a reliable stop under the lower unit to avoid distortion.
The middle class (8-20 hp) requires more serious dimensions, and not only weight, but also the length of the lower unit, which can be standard (S) or long (L). The difference in length is about 15 cm, which is critical for the height of the rack. Sizes of the stand You need to take into account this stock so that the screw does not rest on the crossbar.
Heavy motors (30 hp and above) often have a remote control system and a hydraulic or electric tilt. For them, the size of the rack increases in proportion to the dimensions of the lower unit and the total weight.
Table of conformity of dimensions and capacity
So that you don't have to do complex calculations on your own, we've created a summary table, which is based on averages for the most popular brands, like the ones that you see in the past. Honda, Suzuki and ParsunUse them as a starting point when you're making a drawing.
| Power class (hp) | Recommended height (cm) | Base width (cm) | Pipe diameter (mm) |
|---|---|---|---|
| 2 - 6 | 85 - 90 | 30 - 40 | 20x20 |
| 8 - 15 | 90 - 95 | 40 - 50 | 25x25 |
| 20 - 40 | 95 - 105 | 50 - 60 | 30x30 |
| 50 - 115 | 100 - 110 | 60 - 80 | 40x40 |
| 115+ | 105 - 120 | 80 - 100 | 50x50 |
Notice that the height in the table is indicated with a margin. It is better to make the rack a little higher and put the bar under the base of the engine than to face a situation where the screw scratches the floor. Geometric dimensions The table is relevant for standard dayswoods.
If you have a motor with an elongated lower unit (denoted by the letter L in the marking), add to the height of the rack at least 15 cm For ultra-long dayswood (XL) the stock should be already 30 cm or more. Ignoring this rule will lead to the fact that the motor will have to be put on the rack at an angle, which is harmful to the oils.
⚠️ Note: When using engines with an oil injection system (e.g. some models) Yamaha HPDI) store them strictly vertically to avoid suffocation of the oil system.
Materials and their impact on the dimensions of the rack
The material choice directly affects the final dimensions of the structure: steel is stronger but heavier, which requires a more massive base for stability. Aluminum is lightweight and does not rust, but to ensure the same rigidity, you have to increase the section of the profile, which visually makes the rack more cumbersome.
Wood is also used to create temporary or budget stands, but wood tends to absorb moisture and deform. If you choose wood, the size of the bars should be with a margin: instead of 40 x 40 mm, it is better to use 50 x 50 mm or 60 x 60 mm for reliability.
Plastic and composite materials are found in prefabricated factory solutions, lightweight but limited in weight. load-bearing capacity Such racks are often lower than the declared one, so when choosing a plastic model, always round the required load capacity in the large direction.
Combining materials can create an optimal balance, such as a steel base for weight and stability, and an aluminum vertical rack for lightness, in which case the size of the interconnectors should be calculated taking into account the difference in the coefficients of thermal expansion of metals.
Step-by-step instructions for calculating individual stand
If you don't have a standard size, you'll have to take individual measurements, which is a simple process that requires only roulette and care, and the accuracy of the calculations will save your motor from future damage.
Start by measuring the length of a lower unit. Apply the tape measure from the mount plane to the transom to the lowest point of the screw (not the blade, but the hub). This will be the base value for determining the height of the vertical pipe. Then add 5-10 cm of stock so that the screw is guaranteed not to touch the horizontal bar.
Next, measure the distance between the centers of fasteners on the lower unit. Standard values are 114 mm (4.5 inches) or 216 mm (8.5 inches), but there are exceptions. support-structure.
Remember to consider the type of mounting. If you have a rumpled motor, the gas handle can protrude to the side, in which case the width of the rack should be increased so that the rample does not rest against the vertical pillars of the frame when installed.
⚠️ Note: When calculating height, consider the height of the operator. The upper edge of the rack should be at the level of the belt or slightly higher, so that it is convenient to put the engine in place without assistants.
Mistakes in Sizing and How to Avoid Them
One of the most common mistakes is ignoring the weight of the fuel tank: a full-tank engine weighs significantly more than a dry unit. If the stand is designed to be "back-to-back" in strength, it can fold or bend under additional load.
The second mistake is that the base is too narrow, and in the heat of the garage space-saving struggle, the owners make 20cm-wide racks, which is absolutely not enough, the slightest touch with the shoulder, and the 40kg motor flies to the floor. Security It should always be a priority to save space.
The third mistake is the wrong choice of height relative to the exhaust holes. If the rack is too low, the exhaust fumes (when started on a riser) can bounce off the floor and enter the air intake zone, although this is less critical when stored. It is more important that the water draining after washing does not stagnate in the lower unit due to the wrong angle of inclination.
Also, the wheels are often forgotten. If you're planning to move the motor around the garage, consider that the wheelbase will increase the overall height of the structure. The dimensions must be recalculated to reflect the diameter of the wheels so that the screw still doesn't touch the ground.
Frequently Asked Questions (FAQ)
Can I use one stand for motors of different power?
Yes, if the design is universal. Usually these are high racks with a wide base and adjustable stops. However, for very light (2 hp) and very heavy (100 hp) motors, it is better to have separate solutions, since their center of gravity is different, and stability will be compromised.
What is the minimum gap between the screw and the floor?
A gap of at least 10-15 cm is recommended, this will protect the screw blades from chipping in case of accidental impact on concrete or asphalt, and also ensure normal air circulation around the gearbox.
Do I need to remove the engine from the stand for the winter?
No, the stand is designed for long-term storage, and the key is to make sure that the motor is upright and the gearbox is water-free, and some people recommend raising the lower unit slightly, but a standard vertical rack is the best option.
Does the material of lower unit (aluminum) affect the choice of rack sizes?
lower unit material affects weight, but not dimensions. Aluminum lower unit is lighter than steel equivalents of the same power, but its geometric dimensions (length, width of attachment) are standardized, so the dimensions of the rack remain the same.
Can you make a stand out of wood?
Yes, you can. Use dry hardwood or quality timber. The cross-sectional dimensions should be increased compared to the metal (at least 50 x 50 mm for racks). Be sure to treat the tree with antiseptic and varnish.