Second hand hovercraft buyers guide

Article by Michael Nell

Edited 17th November, 2017.

Introduction

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 build.

The value of any secondhand hovercraft can be hard to estimate when you cannot compare it against a new or second hand hovercraft of the same make. I urge people to look around. Do your research. Do not buy the first hovercraft that you see. Do not buy on looks alone. Do not buy 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 and even over state 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 needs attention. Do not be scammed into buying a hovercraft on impulse.

Some sellers know very little about the hovercraft they are selling. It has either been handed down to them, bought at a auction or found at a junk yard or rubbish dump. 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 in the first place, 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 can be 20 to even 40 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 in reality is only worth $2,000, or built from scarp parts and 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.

Many 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. It is advisable to get a second opinion.

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. .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 ?

Here is an example (not all) of the most common small hovercraft designs in Australia (under 5m, listed roughly in order from the late 70`s).

Neoteric / Neova - Fiberglass. Integrated. Finger skirt. Belt reduction drive. Reverse thrust buckets. Several designs produced by Neoteric Engineering. The company moved to the US in the early years but still retains a office in Victoria.
Explorer - Fiberglass. Bag skirt. Belt reduction drive. Twin fan ducts. 3.4m x 1.8m. I believe it originated in South Australia. Just a handful made during the 80`s. Powered by a EC44 Robin.
Hoveroo - Fiberglass. Integrated. Finger skirt. Direct drive. 4m x 2m. Unknown origin. Produced during the early 80`s. Powered by a VW engine. Just a handful made.
Hoverlight - Fiberglass. Integrated. Bag skirt. Direct drive. Semi enclosed cabin. Unknown origin. Produced during the early 80`s. Powered by a VW engine. Just a handful made.
Hoverjet - Fiberglass. Bag skirt. Separate lift and thrust. Produced by Owen Ellis in the early 80`s. Typically used a small Solo or Robin lift engine with a EC25 thrust engine.
Turbo 225 and 235 Superwedge - Plywood / Fiberglass. Integrated. Finger skirt. Belt reduction drive. 3.3m x 2m / 3.5m x 2m. Produced by Turbo Hovercraft in the late 80`s. Supplied made or sold as a plans/kit. The 225 used a EC44 Robin. The 235 used a PE485 Yamaha.
Expo and Razor- Fiberglass. Integrated. Finger skirt. Belt reduction drive. 3.3m x 1.8m / 3.8m x 2m. Produced by Queensland Hovercraft supplies from the late 80`s to early 90`s. Used either a PE485 Yamaha, Rotax 532 or 582 silver head. (sometimes called a extended Superwedge).
Aqua Terra - Fiberglass. Integrated. Finger skirt. Belt reduction drive. 3.2m x 1.8m. Produced in Western Australia in the mid 90`s. Variety of engines.
Hornet - Fiberglass. Integrated. Finger skirt. Belt reduction drive. 3.8m x 2m. Produced by Hornet Hovercraft / Hoverservices Pty, Ltd. in South Australia in the mid 90`s. It used either a 3 cylinder Polaris two stroke, or EA81 Subaru.
Hovercruise 5/6 - Fiberglass. Integrated. Finger skirt. Gearbox drive. 3.8m x 2m. Produced by Hoverworld in Queensland in the 90`s. Used a PE485 Yamaha and Rotax gearbox.
Turbo/Votex 245, 265 and E2 - Fiberglass. Integrated. Finger skirt. Belt reduction drive. 3.5m x 2m. Produced by Turbo Hovercraft and Votex Hovercraft from the late 80`s through to mid 20`s. The 245 mostly used the PE485 Yamaha. The 265 used a Rotax 532 and latter models, the 582UL. The E2 uses the Rotax 582UL.
Rocket/Renegade - Fiberglass. Integrated. Finger skirt. Belt reduction drive. 3.4m x 1.8m. Produced by RecTech from the mid 90`s. Early Rockets used a PE485 Yamaha. Last of the Rockets used a 500cc Yamaha Vmax. The Renegade (same hull as the Rocket) commonly uses a 25 - 40hp Kohler or Honda V Twin industrial four stroke. Models from the late 90`s used a rear drive or Redrive (fan driven from behind).
Mariah 425 and 486 - Fiberglass. Integrated. Finger skirt.  Belt reduction drive. 4.2m x 2m / 4.8m x 2.5m. Produced by Mariah Hovercraft in Victoria from the late 90`s. Initial 425 model used a Yamaha 500 or 600.Vmax. Currently using a Yamaha R1 1000cc four stroke on both medels.
Viper Cruiser - Plywood / Fiberglass. Integrated. Finger skirt. Belt reduction drive. 4.1m x 2.2m. Produced by Viper Hovercraft from the late 90`s. Supplied  as a plans/kit. Early series used a Rotax 503. Latter and current series use a Rotax 582 or Hirth 32**.
Viper 4, 4X and Viper 5, 5X - Fiberglass. Integrated. Finger skirt.  Belt reduction drive. 4.1m x 2.2m / 4.6m x 2.2m. Produced by Viper Hovercraft from 2000. The early Viper 4 used either a 582 Rotax , 2706 Hirth or 3203 Hirth (up until 2007). The series 2 Viper 4 to current uses a Rotax 582, Hirth 3202 or 3203. The early Viper 4X mostly used a Hirth F30 or Jabiru 2200. The last of the Viper 4X used a Hirth 3003. The early Viper 5 used a Rotax 582 until 2011. The current Viper 5 uses a Hirth 3701V. The Viper 5X uses a Hirth 3701VS or ES.

Imports

Scat - Fiberglass. Integrated. Finger skirt. Scat was our biggest importer from the late 80`s to early 90`s. These included the Scat 1,11 and HP. The Scat 12, Rescue and Liberator. The Scat 1 (pre 1990) was powered by a Rotax 277 via a belt drive. All following models used a gearbox. The pre 1990 Scat 11 had used a Rotax 277. The following models used a Rotax 503 or Cuyuna UL2. Both pull start only. The Scat 11 HP used a Cuyuna 430HP electric start. The early Scat 12 and Rescue used a Rotax 503, however latter models arrived with a Rotax 532. The Liberator used a 582UL.The Scat 1 and 11 was 3m x 1.8m. The Scat 12 and liberator was 3.5m x 1.8m.

There have been a small number of imports such as Aerocruiser, Jet Hover (Sumitomo), Hovpod, BBV, Flying Fish, Osprey, Hoverguard and Slider. You may find information about most of these on the internet.

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 (just my opinion).

The Engine

The engine is the most expensive part on a small hovercraft.. Most small hovercraft use a two stoke light aircraft or used snow mobile engines. These engines are used as they offer the best 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 of a the engine, will generally determine the value of the hovercraft.

Two stroke Engine models

Rotax - In the light aircraft two stroke range, Rotax produced the 277, 447 and 503 air cooled, and the 532, 582 and 619 water cooled. The 447, 503, 532 and 619 are no longer in production, but parts are still available.

The 277, 447, 503 and 532 engines can be found in older production hovercraft, home built hovercraft and imported hovercraft. The CDI version of 447 and 503 is the better engine and the 532 had CDI ignition as standard. In general, avoid engines with Points ignition.

The Rotax 582 silver head series engine has been in production for some time. There are many variants other than the Ultra light aircraft series (UL) fitted to snow mobiles and Jet skis. In 1999, Rotax released the Blue Head 582 UL99. This would be one of the most popular 64hp Rotax engines fitted to modern small hovercraft. You will find these engines in the Turbo 265, E2 and Viper 4 models.

Typically, a two stroke Rotax engine will need a top end overhaul 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.

Hirth - Hirth engines are becoming a popular engine for new small production Hovercraft, The early series were not very good (to be brief) but engines produced from 2000 are proving reliable. In Australia, a small number of pre 2005 production hovercraft are fitted 27** series. This series has been replaced with the refined 32** series. These are 55hp - 65hp air cooled two cylinder engines used in many small modern hovercraft around the world. Many small hovercraft are fitted with the 100hp, flat four cylinder F30. The refined version of this engine is the 3003, which is the better model (if you can find one). The 3701, 3 cylinder water cooled engine was released around 2005. This engine is a very popular in 100hp powered hovercraft around the world. The newer series of Hirth engines (post 2005) are the better engines and well suited for salt water use. You will find Hirth engines in some Turbo 245, Viper Cruiser, Viper 4,42 ,4S2, 4X, 5X, 5XR and Neoteric.

A Hirth engine will need a top end overhaul at around 750- 1000 hours (if looked after and treated well), and the crank replaced at around the same time.

Robin (Fuji Heavy Industries) - Robin produced a number of EC series engines which are fitted to many small hovercraft from the 70`s to mid 80`s. The EC44 was the most popular engine fitted to small integrated hovercraft. The EC25 was used as a small thrust engine or lift engine. Most lift engines were the EC10 or EC17. You will find these engines in hovercraft such as the Turbo 225, Hoverjet, Eclipse and Explorer.

Polaris - A small number of hovercraft in the late 80` are fitted with a three cylinder Polaris, such as the Hornet, produced in South Australia.

Yamaha - Yamaha produced a 480cc engine well over 20 years ago. This was the PE485. This engine was used in snow mobiles, but Yamaha also sold this engine as a create engine. This engine was fitted to many small hovercraft such as Turbo Kits, Turbo 235, 245 and Turbo Wedge, Expo, Razor, 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.

Yamaha also produced a water cooled 500cc, and 600cc engine called the Vmax. This engine came from a 90`s series snow mobile. It was not sold as a create engine, but some new engines were specially imported. You may find these engines in early Rockets and Mariah hovercraft.

High performance two stroke engines

The most common we may see here, is the Rotax 495, 583, Rotax 600 series twins, Rotax 800 series 3 cylinder and Yamaha 500 or 600 Vmax. These engines produce high power and  reach 8,500 rpm or more. These engines are ideal for small racing hovercraft, but are not well suited for larger recreational hovercraft. Engine life is around 120 hours at best.

Two stroke engine checks

When inspecting a hovercraft fitted with Rotax, Hirth or Yamaha (or any two stroke for that matter), it is important to at least check the basic things. Look for any signs of corrosion. 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, crankcase and fuel leaks.

On older hovercraft, exhaust systems may have rusted badly if not specially coated. Ensure that the exhaust has not been modified (shortened or extended beyond standard) and it is the correct exhaust for the engine. A modified or incorrect exhaust system can reduced power, overheating, engine damage and reduce a engines life. Also ensure that the exhaust noise level meets Australian standards.

If possible, do a compression check. It should be a minimum of 115psi (they are around 125psi new). Ensure both cylinders are within 10% of each other. Low compression is usually worn rings combined with piston slap. If there is no piston slap, this may indicate that the rings are stuck in the piston groove, usually from long term storage or too much oil in the fuel.

Visual internal engine inspection via the sparkplug holes and exhaust ports can point out engine damage or issues. Look for scores on the exhaust side of the piston. Ensure both rings move freely in the groove. Look for deterioration (melting) on the exhaust side of the top of the piston.

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 and 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 here are some warning signs.

- Slow to respond or will not reach full RPM.
- Lots of smoke even after the engine has warmed up.
- Engine noise such as piston slap or crankshaft bearing noise
- Misfiring under load, back firing etc.

Four stroke engine models

The most common four stroke engines used in Australian produced small hovercraft are Subaru car engines, light industrial engines and a small number snow mobile engines.

A Subaru is commonly used in larger designs, and recently, to replace a aging two stroke engine. Not all Subaru installations are good, and in general, the hovercraft can be heavy. It will take an experienced person to fit one correctly, in a manner that suits the design weight.

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 or Hirth, 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, and be quiet. 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 great performance.

Some small hovercraft are fitted with a modern four stroke snowmobile engines, These engines declare a high power output exceeding 10,000rpm, but when driving a fan or propeller, the realistic power output is considerably less. The cost of a second hand snow mobile engine is a fraction of the cost of new light aircraft engine. This should reflect in the buy price.

Four stroke engine checks

It is important to at least check the basic things. Look for any signs of corrosion. Query about how many hours it has done. Listen for any piston slap or knocking from the crankshaft. Look for oil and fuel leaks.

On older hovercraft, exhaust systems may have rusted badly if not specially coated. Ensure that the exhaust noise level meets Australian standards.

If possible, do a compression check. It should be a minimum of 150psi. All cylinders should be within 10% of each other. Low compression is usually worn rings or valves.

Remove the dip stick. The oil should be clear, not black or brown.

Remove the oil fill cap and breather hose. Thick sludge on the cap or inside the hose will indicate worn rings or the oil has not been changed or changed regularly. Light brown sludge on water cooled models indicates a blown head gasket.

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 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 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 here are some warning signs.

- Slow to respond or will not reach full RPM.
- Any signs of exhaust smoke, even after the engine has warmed up.
- Engine noise such as piston slap or crankshaft bearing noise
- Misfiring under load, back firing etc.

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.

Hull designs

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 specially shaped hulls to reduce drag when the hull contacts the water.

The hull must have adequate buoyancy such as water tight or foam filled compartments. The buoyancy system must be capable of supporting the weight of the hovercraft and persons on board if the cockpit is flooded. Hovercraft with foam filled cavities are much stronger overall and will still float if the hull is damaged. Hovercraft without such floatation will sink once the water enters the plenum chamber via the skit feed holes. Many imported hovercraft do not have adequate flotation.

Fiberglass Hovercraft

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 

Kit / plywood Hovercraft

The most common Australian plywood / kit hovercraft are the Turbo wedge and Viper Cruiser. These hovercraft models are well suited to Australian inland and coastal conditions.

The most common overseas plans are Universal and Sevtec. These designs are well suited to inland waters, rivers and clam conditions.

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.

Look carefully 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 de lamination 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.

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.

Fans and propellers

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.

Look carefully at all the fan blades and fan hub. The fan blades should be free of any chips and cracks. Look for and corrosion build up on the hub especially between the matting surfaces. Rusted bolts is not a good sign. A well cared for fan assembly will be clean and free of any corrosion.

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.

Propellers can be a unknown, but check for chips and cracks. Wooden and composite propellers should have a leading edge protection strip installed. Water droplets, sand and dust can easily wear the leading edge away if unprotected.

Drive systems

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 low 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.

Skirts and Skirt systems

A skirt on a hovercraft are like tires 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.

Check that the skirt is the right skirt for the type of model. We have seen many secondhand hovercraft fitted with finger skirts on a hull designed for a bag skirt.

It is not important that a second hand hovercraft has a worn skirt, as it means, its being used and it works. If the skirt looks and feels brittle, it is a sign that the hovercraft has spent much of its time outdoors. If the skirt is brittle, but hardly worn, this could mean several things. It may have been hardly used, or it does not work.

The type of skirt material is important. For anyone new to hovercraft, it would be hard to tell the good material from the bad. Here some minimum requirements.

- The skirt backing material should be made from Nylon fibre.
- It should be coated with either neoprene, polyurethane or PVC.
- It should have good bias strength, so it does not deform under pressure (bulge outwardly).
- It must be flexible to contour to the surface. A skirt that is too stiff, or has a heavy natural rubber coating will fold in forward motion, loosing lift pressure and height. (natural rubber coating is used primarily on hovercraft operating on ice).

Replacing or repairing a skirt is a worthwhile venture, as it will bring the hovercraft back into good service, and resume its correct hover height. If the hovercraft has a worn skirt, maybe you can negotiate a reduction in price to compensate for its replacement.

Summary

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.


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

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