Three cylinder outboards ... pleasure & racing

**Mark75H** · 09-20-2009, 03:11 PM

Without going thru Peter Hunn's Old Outboard Book, the first 3 cylinder that comes to mind was built by Thor ... the predecessor to Merc

1938 & 39

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**Mark75H** · 09-20-2009, 03:15 PM

About the same time Rudolph Konig made a 3 cylinder 2 stroke radial motor in Germany that had a successful racing version

Notice a cylinder pointing off to the left and another to the right at the back; the third cylinder faced forward

**Mark75H** · 09-20-2009, 03:15 PM

Dieter Konig, son of Rudolph Konig ... added a cylinder to his 2 cylinder racer to make a 3 cylinder 30 ci racer

The bottom carb is missing its float bowl.

This motor was unique in its day, using the exotic "Curvic coupling" segmented crankshaft ... fully "tinkertoy" piece together construction. You could literally take the motor apart and remove the center cylinder pieces and reassemble it as a 2 cylinder or a single.

Decades later OMC would use Curvic couplings in the prototype rotary race motors

Another uncommon feature of this motor, there are no reed valves. The carbs feed up into the crankcase, timed by an internal disk valve called a rotary valve.

**Mark75H** · 09-20-2009, 03:17 PM

Another "add a cylinder" twin to become a triple was Scott-Atwater's 40 hp ... becoming the 60 hp triple. Nothing exotic inside this motor, reed valves and a solid crank.

**Mark75H** · 09-20-2009, 03:19 PM

In 1961 McCulloch, the sucessor to Scott-Atwater improved the 60hp triple to 75.2 and introduced a gearshift racing lower unit for it ... the 75hp "Custom"

The differences between the 60 & 75 were piston & head shape, carbs and transfer port covers

The 40 & 60 used a wedge shaped combustion chamber, the 75 uses a hemi shaped combustion chamber

**Mark75H** · 09-20-2009, 03:25 PM

Crescent ... sometime division of Electrolux and Volvo in Sweden ...

Introduces a 3 cylinder triple 30ci race motor

No reeds or rotor for this motor, this motor uses "piston port" intake controlled by the piston skirt

**Mark75H** · 09-20-2009, 03:26 PM

McCulloch introduces a rotary valve intake, full race triple

If you look closely you will see that this motor has the rubber bushing vibration isolation steering connection yoke just like the fishing version in post 5 and timing marks on the flywheel

**Mark75H** · 09-20-2009, 03:27 PM

The full race McCulloch triple is revamped with a better steering connection and minor improvements to the lower unit

2 versions were now available ...

the standard 63.25 ci motor ... the "630"

and

a destroked 59.9 ci motor that qualified to race in APBA "F" class ... the "590"

If you look closely at this motor and compare it to the motor above you will see some subtle differences. The flywheel is thinner, the carbs mount closer to the rotor and the rubber mounted steering yoke is gone in favor of a hard connected steering bracket straight out from the top of the mid. This motor also has "overflow" & return carbs instead of floats.

**Mark75H** · 09-20-2009, 03:29 PM

OMC introduces their 49 ci triple ... 55 hp

**Mark75H** · 09-20-2009, 03:31 PM

Known only in Europe, OMC makes a race version of the triple with the "X-115" race lower unit

**Mark75H** · 09-20-2009, 03:31 PM

Merc introduces a 3 cylinder 49 ci triple

**Mark75H** · 09-20-2009, 03:34 PM

Dick O'Dea convinces APBA to put the gasoline burning version of the Crescent racer in its own Stock Outboard class and the Crescent is reborn after the full race alcohol version is obsolete

The class was named "C Super Stock Hydroplane" but earned the nickname "Super C"