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
Size: 80L x 35W x 23H (cm)
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. RECORD SETTER
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 horse power. 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 later. 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 boats.