In the 1930s and
1940s, loud, fast racecars were entertaining the masses,
allowing automobile manufacturers to show their engineering
prowess and providing a way for wealthy sportsmen to get their
kicks. But automobile racing wasn’t the only show in town.
Championship speed boat competition, in the form of nautical
circuit racing, endurance racing and flat-out top speed record
chasing were popular the world over.
Just as auto manufacturers were developing engines and race cars
in cooperation with thrill-seeking rich guys, those same racing
motors made attractive power plants for builders of competition
boats. As we all know, publicity and advertising foot the bill
for competition. In Italy, auto manufacturers such as Alfa Romeo
and Maserati took pride in teaming up with Italian boat racers
by supplying them with retired racecar power plants.
Achille Castoldi was one such wealthy boat privateer. In 1940,
Castoldi set the world speed record of 81.10mph in the 400kg
class with his boat Arno, a Picciotti hull powered by an Alfa
Romeo type 158 engine. Castoldi subsequently built a number of
Arnos, mostly with Alfa engines, but at least one was powered by
a Maserati racing mill. In 1952, Castoldi severed his ties with
Alfa Romeo, or maybe Alfa severed their ties with Castoldi? It’s
not clear one way or the other.
TIMOSSI FERRARI ARNO XI
For 1953, Castoldi decided to focus less on circuit racing, and
to concentrate on setting top speed records. He commissioned an
800kg-class three-point hydroplane hull to be built by Cantieri
Timossi, a hydroplane builder on Lake Como, near Milan. The
hydroplane was constructed with a solid wood frame skeleton with
a marine plywood skin and a mahogany veneer. The aluminum
fairing, rear aerodynamic stabilizer and engine cover were
painted in red, the traditional color of Italian racers. The
hull was dubbed Arno XI. For the engine, he turned to the new up
and comers of the auto racing scene – Scuderia Ferrari.
Ferrari supplied Castoldi with a type 375 V-12 Grand Prix
engine, the same type that powered Ferrari’s racecars in ’51 and
‘52. The supplied engine displaced 4493.7cc, each cylinder with
an 80mm bore & 74.5mm stroke. There were two spark plugs per
cylinder, a 12:1 compression ratio and the stock engine made
approximately 385bhp. Ignition was handled by magnetos, rather
than a distributor and coil.
The engine was mated to a gear step-down box which spun the twin
bladed propeller at up to 10,000 rpm. The propeller shaft ran at
a shallow downward angle toward the rear of the hydroplane (the
angle got steeper, of course, as the aerodynamics of the
three-point hull lifted the bow of the boat at speed). The
propeller shaft and the engine both were kept cool by the fresh
water of the European lakes where the boat raced.
At the January 1953 Campione d’Italia races, Castoldi piloted
Arno XI to an unofficial top speed in excess of 124mph during
the shakedown testing, prior to the official two-way run. His
rival, Mario Verga, had taken Castoldi’s place at Alfa Romeo,
who were lending their full official support to Verga, including
their technical staff and press officer. Verga managed to set
the 800kg-class speed record of 125.68mph with his Alfa 159
powered Laura. Two weeks later, he surpassed his own record with
a two-way top speed of 140.74mph.
In preparation for another attempt at breaking Verga’s new
record, Castoldi had a new engine built with twin superchargers,
which compressed the air and fuel delivered by a pair of massive
4 barrel Weber carburetors. The engine was tuned to burn
methanol, which allowed the compression ratios to be increased
and the superchargers to produce plenty of boost with less risk
of detonation. Arno XI’s new methanol burning, twin supercharged
4.5L Ferrari power plant produced between 550 and 600 brake
Enzo Ferrari sent Stefano Meazza, the chief race engineer of the
Scuderia, to help prepare the new supercharged engine. Grand
Prix champion Alberto Ascari and driver Luigi Villoresi showed
the support from the Scuderia by attending the event. On the
morning of October 15, 1953, Achille Castoldi succeeded in
smashing the 800kg class speed record with an average “flying
kilometer” two-way speed of 150.49 mph. Ascari and Villoresi
boarded a small boat and pulled up alongside Arno XI to
congratulate their friend Castoldi. He followed up the
performance later that day by setting another record in the “24
nautical miles” event with an average speed of 102.34 mph.
Castoldi retired from hydroplane racing in 1954, after a scary
and violent engine failure while traveling at high speeds in a
new airplane-engined 1700kg Timossi hydroplane. His rival, Mario
Verga, died in a separate hydroplane accident a short time
Achille Castoldi sold Arno XI to a wealthy engineer named Nando
dell’Orto. Ingnere dell’Orto revised the body lines of the
engine cover and front fairing, added a large fin behind the
driver for stability, and raced the boat for a few more years.
The most notable success was a 2nd place finish in the 1965
900kg World Championship.
Arno XI was restored in the early 1990s and was put up for
auction at the Coy’s Festival at Silverstone in 1997 where it
did not sell. It was photographed skimming across the water as
recently as September 2004, along with many other vintage racing