NSW Hydroplane Club - Boat Profiles & Photos

Australian Inboard Hydroplane Classes

Elsewhere on our site the concept of a hydroplane is shown, together with photos of boats in various "classes". A boat is classed according to the capacity of it's engine, subject to some rules.

Over the years the Australian Power Boat Association (APBA) has developed it's own classes of hydro racing, generally separate from those of the UIM, but sometimes superficially akin to those of our American counterpart. Apart from similar cubic inch motor limitations, the Australian approach was and is more freewheeling. Generally speaking, there has been little restriction on engine makes, models, fuel injection, overhead camshafts, fuel type, hull dimensions or weights. Following from pre-World War II makes, engines have included locally built Holdens (Aussie branch of GM) and Fords, together with Chevs, Chryslers, Jaguars, Coventry Climax, Puegot, Fiats, Maseratis and latterly Toyota and other Japanese motors. THe occasional Mercedes has found it's way into a hull and a couple of Rolls Royce Merlins into Unlimited Hydros.

Many Classes familiar from the early days have long since been retired, eg. 91ci (1.5 litre), 135ci, 225ci and 266ci. THe 1.5 litre was an international class and it was in this that Australia established it's first world record; in 1950 Keith Barry drove his MG powered hydro "Firefly II", to a record of 72.3mph (116.2kph).

Engine capacities are now expressed in litres. There are thirteen hydros classes currently recognized by the APBA. Most of these are inactive because of lack numbers at championship level. The APBA however, leaves records open to attack for many years before a final retirement decision is made. Consequently, some marks may date from the 1960's, eg. the 0.85 litre record is 126.7kph (78.7mph), 1.75 litre is 165.2kph (102.6mph) and 4.5 is 196.9kph (122.3mph).

Today's active classes include 1.6 litre stock, 3.75 litre, 4.2 litre stock, 5.2 litre, 6 litre and Grand Prix. While there are unlimited hydros in this country, an unlimited event here is essentially an "open" hydro race. Smaller hydros may as a general rule, compete in larger classes with some restrictions.

The following is a summary for general interest only. Full requirements are in the APBA Rulebook and from the appropriate class registers.

Lil Shocker
1.5 litre hydro Firefly II

3.75 litre Lil Shocker

Rolls Royce powered Aggressor

1.6 litre
The 1.6 litre class allows either of two models of the 1600cc DOHC Toyota 4 cylinder engines. The only changes permitted are the substitution of two dual throated Weber carbies for the factory fuel injection system. The use of an aftermarket computer used in conjunction with the stock injection is allowed. Dry sumps are allowed. Pump petrol (gasoline) as obtained at service stations is the only legal fuel.

The kilo mark stands at 161.4kph (100.3mph).

4.2 litre
The 4.2 litre class is based on the 1970's Holden V8. Except for the camshaft which may be of any make or grind, only standard Holden replacement parts are permitted. The cylinders may be overbored a maximum of 0.040 inches. Compression may be raised by the removal of metal from the block or heads. (no domed top pistons) with a minimum combustion chamber volume of 53ccs. The standard intake manifold must be used with one four barrel carbie, either Rochester or Holley. Porting, polishing or larger valves are not allowed, nor is magneto ignition. Balancing, stronger springs and dry sumpimg are permitted. Fuel is restricted to pump petrol. Though 320 bhp has been registered on a dyno by a legal motor, 300 is generally quoted. Engines will run safely up to 7200rpm.

The kilo record is 200 kph (124.4mph)

A 4.2 litre boat Research

5.2 litre & 6 litre
The 5.2 & 6 litre classes are restricted only by engine capacity and av gas or methanol may be used. Super/turbo charging is allowed, but a penalty applies. A factor of 1.7 is applied to actual capacity to determine the class capacity. Thus a 3 litre supercharged engine would make it the equivelant of 5.1 litre (3 x 1.7 = 5.1), and therefore run in the 5.2 litre class.

The record for the 5.2 litres is 214 kph (133.3mph)
The record for the 6 litre class is 230.4 kph (143.2mph)

6 litre boat Mistic Miss

Grand Prix Hydroplane
GP hydro is the only class where dimension and weight requirements are specified (though a general rule allows a maximum length of 9.14m / 30 ft for all hydros). The maximum length of a GP is 8 metres (26' 3") and if supercharged the boat must weigh no less than 1080kg (2380 lbs). Engines must not exceed 510ci (8.26 litres), there being no penalty for supercharging, be iron block, two valves per cylinder, with methanol allowed.

While reinforced cockpits are now required on all new hulls, those built prior to this rule may still be raced. A hydro field may thus comprise of Rear Seaters and Cabovers with and without reinforced cockpits. Inboard tunnel hulls (also known as KTs) are generally raced with hydros except in a hydro championship event. All hydroplanes must be driven by a propeller acting against the water. Nitrous Oxide and nitro fuels are allowed only in Unlimiteds.

There are many hydros running in Australia which do not meet the above class requirements. These compete in non-class events, as indeed do the class specific boats from timr to time.

Australia has a long and colourful history of hydroplane racing, dating from stepped hulls of the early 1900s. The NSW Hydroplane Club continues the tradition by fostering new boats and drivers.

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GP boat Latimer Lodge

Impatient with a reinforced cockpit

Older rear seater Swap, without a reinforced cockpit

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