2019 Seafair Commemorative Magazine

EVOLUTION OF THE
HYDROPLANE
When Stan Sayres drove the Slo-mo-shun IV to a
new World Water Speed Record of 160.323 mph
on Lake Washington on June 26, 1950, you could
buy a brand new Ford Crestliner for $1,624.00, and
a gallon of gas was 18 cents. There were only two
TV stations in Seattle (KING and KOMO), and if you
wanted to drive to Portland, you would have to take
Highway 99.
The Slo-mo was built almost entirely out of wood
and weighed about 4,550 pounds. The Slo-mo was
a round-nosed hydroplane that was powered by a
1710 cubic inch V-12 Allison engine originally built
for the P-38 Lightning airplanes in World War II. The
engine used a three-to-one step-up gear box to
turn a two-blade propeller at almost 12,000 RPM.
The driver sat behind the engine in a wide-open
cockpit and often wore street clothes, sometimes
20
including a tie and penny loafers. Drivers didn’t
wear seat belts for fear of drowning, but they did
wear kapok life jackets and helmets made from
fiberglass and leather.
Race boats tend to evolve quickly because racers
are always trying to go faster, and the only way
to go faster is to try something new. The biggest
change that hydroplanes went through in the
1950s was a switch away from the Allison to the
more powerful Rolls Royce Merlin that had been
used in Spitfire and P-51 Mustang airplanes during
WWII. Switching to the Merlin allowed the boats to
increase their speed by almost 10 miles per hour.
The faster speeds that came with the Merlins led
to a new and frightening type of accident called
“stuffing,” where the boat takes a nosedive at high