outboards were manufactured by the Hart Carter Corporation in New
Holstein Wisconsin from the 1940's through the mid 1950's. They
had long been a manufacturer of engines and other machinery, mostly
for farm use. Lauson outboards were billed as the "Cadillac"
of outboards for fisherman and sported a number of innovative features,
the most unique being that all of their outboards utilized 4-cycle
engines. The advantages of 4-cycle engines are high fuel economy
and excellent slow speed operation compared to contemporary 2-strokes.
Carter sold out to the Power Products (Tecumseh) Company in the
mid 1950's and they did not elect to continue outboard production.
Lauson S-351 3hp
S-350/351 Owners Manual pdf
Year & Model:
1951 Lauson S-351
Ignition: Wico Magneto
Point Gap: .020
Cooling: Forced air-cooled
Retail price when new: $129.50
Weight: 48 lbs.
Oil/Gas Mix: None! 4-Cycle
Spark Plug: Champion J-8
Lauson S-351 3hp
is my restored 1951 Lauson S-351 3hp outboard - it took the remains
of three to put this motor back together. It is a single cylinder
4-stroke with the valves "in-block" and is air cooled
by a force draft down from the fins on the side of the flywheel.
The block is cast iron with the crankcase, leg and other parts made
of aluminum. It is a heavy motor for 3hp weighing in at the equivalent
of motors with twice its horsepower. The magneto is fixed and throttle
is by the small side draft Tillotson carburetor. Crankcase oil is
filled and checked on the port side of the motor, the engine is
even equipped with a mini oil pump for the crank ends, connecting
rods and valve cam! The motor is equipped with handy features like
an easily adjustable knob for the co-pilot (tiller friction) and
a little compartment in the tiller to store shear pins.
S-351 starts relatively easily, often requiring 3 or 4 pulls when
cold and one or two when warm. It idles superbly and is reasonably
quiet and smooth up to the mid-range. The top end is another story...
the whir of machinery and vibration become quite unpleasant. Fuel
economy is excellent at the low and mid range but I couldn't stand
running the motor long enough at top end to make an accurate assessment
of its economy. Power, in my estimation, is close to the rated 3hp.
am in the process of restoring a T-651 6hp twin. It is basically
two of the 3hp engines combined in a fore & aft opposed twin
configuration. The twin is not as "clean" a design as
the single and is assembled in a manner Rube Goldberg (ace bodger)
would appreciate! After 4 years of working on the twin the last
part I need is the front engine cowl - hopefully a picture of it
completed will be seen here soon.
Someone asked the location of the ID Tag - it is in the photo below. (Same location on the T-651)
Lauson 4-Stroke Outboards
the early 1940's and just after WWII Lauson produced the OB-410
a small single cylinder 2.5hp outboard. Starting in 1948 Lauson
single and twin cylinder 4-stroke outboards have a model I.D. tag
below the power head on the transom saddle. The serial numbers break
down roughly as follows:
S-350 = 1950
S-351 = 1951
S-352 = 1952
S-353 = 1954 to 1956
T-6 50 = 1950
T-651 = 1951
T-652 = 1952
T-653 = 1954 to 1956
R = Gearshift
of the 300 and 600 series motors were of 4-stroke design, a good
SAE 30 or SAE 40 motor oil should be used in the crankcase. The
On/Off knob on the front of the engine kills the spark and also
closes the crankcase breather so the engine can be transported without
losing oil. Despite Lauson's best efforts, small oil leaks at the
bottom seal and power head base are common- so I keep a drip pan
under the engine when it is stored.
is by Wico magneto with a point gap of .020, engine timing is fixed.
A number of people have experienced coil failure due to the engine
overheating- see below.
is a simple Tillotson located on the starboard rear corner. Throttle
is achieved by the carburetor alone from the top lever on the front
of the motor. (the bottom lever actuates the choke) Fuel is a good
grade of regular gas.
engine is cooled by air forced by fan blades on the flywheel and
directed over the cooling fins on the cylinder. To properly cool
the lower engine cover must be in place - this is often missing
on these old motors. When the lower cover ( front + back on the
twin) is missing not enough of the forced air passes over the cooling
fins causing the engine to overheat. Prolonged usage is thought
to overheat the coils and cause them to fail, evidence of melted
coil insulation is often cited.
are great running little motors and idle very well and are quiet
up to the mid-range. Top speed can be a little noisy. About the
only down sides to the Lauson's are their weight and the fact that
parts are very hard to come by.
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