Second hand hovercraft buyers guide

Article by Michael Nell

Buying your first small hovercraft can be a daunting process, wether it be new or second hand. If you know little about hovercraft, you can be caught with a lemon that costs more to fix than its actual value, or a one that is worth less than the materials it took to built it.

The value of any secondhand hovercraft can be hard to estimate. It is easier when you can compare it against a new or second hand hovercraft of the same make. I urge people to look around. Do not buy the first hovercraft that you see. Do not buy on looks alone and avoid buying unseen or un tested hovercraft.

Many sellers will string you along with a good sellers pitch. They will tell you how amazing the hovercraft is, to the point of over stating its actual performance. Some will say "The top speed is over 100 kph and it will hover 500mm off the ground". These are outrageous statements for small hovercraft, which only says, they have not flown the hovercraft. Things like, "it needs a tune", or "I have not started it for a while", are usually signs that the engine need attention.

Some sellers know very little about the hovercraft they are selling. It has either been handed down to them or bought at a auction. They are unable to tell you who made it or quote specifications, such as the engine make, engine power, payload capacity etc, In many of these cases the hovercraft are misrepresented because there are no identification tags or logos. The owner may have been given the wrong information when they first purchased the hovercraft, or it has been identified incorrectly by someone with little experience.

Many hovercraft look the same, but they are not the same. Many hovercraft look amazing, but are over 20 to 30 years old. Many have pictures of when it was new or first purchased, and not how it looks today. Many have un clear photos that hide all the imperfections. Some may even try to sell you a small hovercraft for over $20,000, which was built for less than $2,000 using second parts and cheap materials. Without knowing what you are looking at, it is easy to be caught with a lemon, or pay far more than you can insure or resell it for.

Most second hand hovercraft have become un loved toys, or the owner has moved on with other interests. Many of these hovercraft have only been used for a short time, and have only deteriorated from sitting around. With a little TLC, you can bring the hovercraft back to life, but knowing if its worth your time, may need you to ask for advice. Simply sending a picture of the hovercraft to a experienced hovercraft manufacturer can answer a lot of your questions, and get a second opinion.

Below is some of the initial things you should consider.

How old is the hovercraft ?
Is it running ?
What is the condition of the engine ?
Is the engine suitable for hovercraft use, and can you still buy parts for it ?
What is the hull made from ?
Is it a proven design ?
Is the company that produced the hovercraft still in business ?

The engine is the most expensive part on a small hovercraft, if the engine was purchased new. Most small hovercraft use a two stoke light aircraft engine. These are used because they are designed for powering a fan or propeller and offer a good power to weight, which is the key to a good hovercraft. You will also find some smaller hovercraft using light industrial engines. Some hovercraft will be fitted with second hand car or motorbike engines. The age, make and model of a hovercraft, and the condition, age and cost of a engine, will generally help you set the value of the second hand hovercraft.

Rotax made two engine styles. A air cooled and a water cooled. The air cooled engine is no longer in production. These were the 447 and 503 which can be found quite cheaply on Ebay or Gum Tree. These engines are being removed from aging light aircraft and replaced with a new water cooled series. Generally, these engines would be found in older production hovercraft, home built hovercraft, or imported hovercraft using surplus stock. The CDI version of this engine is good, however, I would not pay greatly for a hovercraft fitted with one, especially if it was second hand to start with.

Some small 3 to 4 person production hovercraft built from 1990 - 1999, would be fitted with a Rotax 532. This engine is longer in production was replaced the Rotax 582. The current series Rotax is a Blue Head 582 UL99. Here we can tell a hovercraft's age by the model of engine

Typically, a two stroke Rotax engine will need a top end overhall at around 200 - 250 hours, and the crank replaced at around 500 Hours. A professional rebuild for a Rotax can set you back up to $4,000 or more, so it is important to know what the model and condition is before paying anything. Do not rely on the owners evaluation. Hear it running and have the engine checked by a mechanic.

Some small hovercraft are fitted with Hirth (Hirthmotoren) two stroke engines. The 2706 and the F30 were replaced with the 3203 and 3003 around 10 years ago. The 3701 is used more often than the 3003 these days. The newer series of Hirth engines have improved ignition systems and wiring which makes them well suited for salt water use. Early Hirth engines made 20 years ago can be troublesome, much like early Rotax engines. A Hirth engine will need a top end overhall at around 750- 1000 hours, and the crank replaced at around the same time.

Yamaha produced a 480cc engine over 20 years ago. This was the PE485. This engine was used in snow mobiles, but Yamaha also sold this engine as a kit package. This engine was fitted to many small hovercraft such as Turbo Kits, Turbo 235, 245 and Turbo Wedge, Expo, Hovercruise and a number of other small makes from 87 to mid 90's. The early form was single carburettor, and latter series had twin carburettors. Parts are near impossible to source in Australia. Like many engines of this age used in salt water, they would be suffering from corrosion, especially around the ignition systems (stator, flywheel and CDI connections). These engines were purchased quite cheaply and were used as an alternative to Rotax, which were much more expensive at the time. The Yamaha PE485 usually only lasted 120 hours before it needed a top end rebuild, and around 250 hours for the crankshaft. A small hovercraft fitted with a Yamaha when new, would be well over 20 years old now.

When inspecting a hovercraft fitted with Rotax, Hirth or Yamaha, it is important to at least check the basic things. Look for any signs of corrosion. Do a cylinder compression check and query about how many hours it has done. Listen for any piston slap or knocking and/or grinding from the crankshaft. Look for rear seal and crankcase leaks. Older exhaust systems may have rusted badly, so ensure that it is the correct exhaust for the engine. Look carefully at the wiring. It should tidy and well sealed. All the gauges should work, and the volt meter should rise with a an increase in RPM. Hosing down the engine with water while it is running, may help pickup any electrical issues. Look at the cooling system carefully. On the air cooled engines, check the condition of the cooling fan drive belt. On the water cooled engines, check the level and condition of coolant. Have the system pressure checked if possible. A failed leak down test would indicate blown head gasket. Ask the owner to run the engine through its entire rev range. Most Rotax, Hirth and Yamaha engine should peak at around 6,400 rpm. Make sure the engine has fully warmed up and listen for any misfiring or uneven running under load. It is hard to know exactly what the engine is like internally without removing parts, but a engine that is slow to respond, but reaches full RPM will need a more detailed inspection and possibly a overhall.

A small number of production hovercraft were fitted with Subaru engines. A Subaru is commonly used in light aircraft as an alternative to a Rotax or Hirth. Not all Subaru installations are good, and in general, the hovercraft can be heavy. It will take an experienced builder to fit one correctly, in a manner that suits the design. If you are mechanically minded, or have some hovercraft experience, you can tell a good or bad fitment. If you have neither of these, get professional advice.

In the past and even today, many designs use a light industrial engines to power a separate lift, in a separate lift/thrust Hovercraft. These days, there are a large number of small hovercraft using a V twin four stroke engine to power a integrated design (one fan providing both lift and thrust). Engine life expectancy on these hovercraft is less than a Rotax, Hirth or Subaru, but the replacement engine cost is considerably less. These engines are not designed for marine use as far as corrosion protection, however they can power a small, light weight hovercraft adequately. Not all of these designs perform well and I would compare models before committing to a sale. Be mindful that these engines are working to near there maximum most of the time, so do not expect it to perform as well a two stroke alternative.

Some small hovercraft are fitted with a modern four stroke engine such as fitted to a high performance road bike or snowmobile, These engines may declare a high power output, but realistically, these engines are only producing 80% of the power when fitted to a hovercraft. The cost of a second hand motorcycle engine is a fraction of the cost of new light aircraft engine. This should reflect in the price, but this is not always the case.

Hovercraft without engines. If you know little about hovercraft, this can end up a money pit. Even a cheap $1,000 hull will end up costing considerably more to powered it, especially if it has no fan, drive system or skirt. Most hovercraft have ended up at this stage for a reason, and may end up being a waste of money and time. Just be careful.

Home built designs, regardless of what engines are used, are hard to estimate value, especially when it is one off, or owner designed.. In most cases, they are worth more to the owner than what they are actually worth. This is not to discount buying one, as there are some quite good builds out there, but without seeing the craft running, you are just buying trouble.

There are many kit hovercraft out there, such as Viper Cruisers, Turbo Wedges and Universal (the most commons kits/plans sold in Australia), with proven designs. Here, you are looking at how closely the builder followed the plans, and if the hovercraft is fitted with the correct kit components to suit the design. This will help you resell the hovercraft when and if you ever need to. Most DYI kits and plans are plywood Hovercraft, so you are looking at the hull integrity. Has it deteriorated with age, or was it built using quality materials and resins ? Look for delamination of the joins, straightness and alignment of the panels, and any signs of rot. Tap the panels and listen for hollow spots that would indicate delamination in the plywood. Inspect under the hull for any signs of rot or damage that may lead to timber rot latter on. Look at how well the hovercraft has been fitted, such mountings and wiring. Check the steering and controls. If you are buying online, request current photos. Photos date stamped if possible. Ask for any construction photos if you are buying from the builder. Research each design carefully to know what you are looking at. Video of the hovercraft running and any history available is an advantage. A independent inspection is a good recommendation.

Late model fiberglass hovercraft are worth considerable more than a plywood one, simply because the hull will last longer. Find out the weight of the fiberglass hovercraft as many have been made too heavy. Fiberglass also suffers from a type of cancer if the hovercraft was not made from marine grade resins and gelcoats.  Look for bubbles in the gel coat, cracks or soft spots. Look under the skirt and check for damage to the hull and wear on the landing feet  Check to see if it has adequate flotation. Some hovercraft may float in still water, but sink once the water enters the plenum chamber (common on some imports and cheaply made hovercraft). A hovercraft hull with positive flotation, such as water tight or foam filled compartments are safer, especially in mild to rough conditions. Hovercraft with foam filled cavities are much stronger overall and will still float if the hull is damaged.

Over the years, there have been many imports dating well back to the late 70's. The main problem with imports, especially older Hovercraft, is finding replacement parts, or even knowing what it is. If you are unsure what it is, contact an experienced hovercraft builder. Most older imports are beyond restoration, and if you do find one that is, it is possibly not worth restoring, as it will never compete with a modern small hovercraft. Some small aging hovercraft look amazingly good and well styled, but this does not necessarily mean it performs well. What might impress the neighbours, may end up being a lawn ornament. This goes for all small hovercraft. Before committing to a sale, research the make and model. Do a web check and see if the manufacturer is still in business and find out as much history as you can about the Hovercraft before you buy it.

Hull designs should also be on your list of considerations. Modern hull designs are less likely to plow in. The term "plow in" describes when the forward section of the hull makes contact with the water. This can be a very frightening experience. Plow in can happen in a few scenarios, such as loss of lift pressure, down wind operation, or when the hovercraft is trimmed nose down. How severe the plow in is, depends on the shape of the forward planing panels, and how much weight is above the skirt line. Modern hovercraft have sloped back forward planing panels that plane on the water rather than dig in.

Most small hovercraft are fitted with multi-wing fans. Most old hovercraft are still fitted with the original fan. This is a fan that has reinforced nylon fan blades on a aluminium hub. As these fans age, the blades deteriorate from UV and hubs deteriorate, especially when used in salt water. Personally, I would not trust a fan assembly over 10 years old. The date of manufacture is stamped on the lower section of the fan blades. Replacing a fan is not an expensive process, and in many cases, cheaper than repairing the components it breaks when it blows apart. It is not often that a old fan blows apart on its own, but it does happen. When buying a old hovercraft with a old fan assembly, allow a new fan in your budget.

The most common reduction drive system on a small hovercraft is a tooth belt arrangement. This is the link between the engine and the fan. This configuration has the engine positioned on the engine compartment floor. These hovercraft are generally less noisy and operate more efficiently, as there are no bulky obstructions in front of the fan. They also handle better, as the center of gravity is lower, like a sports car. They are less likely to plow in. There are a number of designs that use a gearbox, as it would be set up in a ultralight aircraft. The engine in this configuration would be positioned directly in front of the fan. These hovercraft are generally noisy and have reduced performance levels because of the air obstruction in front of the fan. These hovercraft are also top heavy, and can be easy to roll over. Hovercraft configured this way, are generally made this way to reduce production costs. Belt drive systems are not immune from problems. Some older hovercraft use low grade nylon pulleys that have either become worn, or were not conditioned for a marine environment. A nylon pulley that has not been conditioned will absorb water and expand to the point where the belt no longer meshes with the teeth of the pulley. Drive systems that have reached this stage, usually have belt jumping issues, which have caused cracks in the engine frame or broken mounting bolts. Care should be taken to inspect the drive system on a second hovercraft. Steel and alloy pulleys, and gearbox's will eventually wear out. Ask the owner to run the engine through its entire rev range and listen for thumping sounds, any irregular shaking from the engine or load gear noise.

A skirt on a hovercraft are like tyres on a car. It is a consumable component that will always need constant attention. A skirt in good condition will add value to a hovercraft. It is not important that a second hand hovercraft has a worn skirt, as it means, its being used and it works. Replacing or repairing a skirt is a worthwhile venture, as it will bring the hovercraft back into good service, and resume its correct hoverheight. If the hovercraft has a worn skirt, maybe you can negotiate a reduction in price to compensate for its replacement.

Used Hovercraft come and go, and many small hovercraft do not sell immediately. With the current economic climate, there are more second hand hovercraft being advertised. There are more buyers looking for second hand hovercraft, as new hovercraft can be an expensive proposition right now. Second hand hovercraft prices have risen over the past few years, but unfortunately, the number of false and misleading adverts have risen as well.

In reflection. If you are new to hovercraft and uncertain about buying a hovercraft, give an experienced hovercraft builder a call. If your are really keen, consider joining a hovercraft club. Take your time to look around at other designs and become familiar with what is out there.

I have not covered all the hovercraft types and engine makes available. I will try to update this section as time permits. Please note that any prices I have quoted are just an estimation based on my experience. I hope the above information has been helpful.


VIPER HOVERCRAFT
A Division of NELL FABRICATION
Goulburn. N.S.W. 2580 Australia
Ph: +61 418649350
sales@viperhovercraft.com.au

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