Archive for February, 2010


Bein’ Green: One of the original 4-stroke outboard motors…

Much has been written and talked about, broadcast and debated about “going green“.  From an outboard perspective, if Al Gore and his tree huggers have their way, we’ll all be running big expensive, heavy 4-stroke outboard motors on our little 1949 Thompson wooden boats.  A modern 4-stroke 30 hp outboard would be roughly a $12,000.00 investment and weigh much more than my 1956 Johnson 2-stroke RD-18.  In fact, the 4-stroke would likely sink our little boat.

However I ran across a recent find which pre-dates the “Green Movement” long before Al Gore and his graphs were ever thought of and “The Green Movement” was a thought in the minds of scientists.  This little motor is indeed a 4-stroke outboard that weighs in around 1/3 the weight of the afformentioned Johnson 30hp.  It produces a “whopping” 2 hp, is air cooled, and loud as hell.  No it is not a typo…2 lousy horsepower!

The motor in question is a 1947 Lauson OB-410 4 stroke 2 hp outboard motor.

The orignal "Green Machine". Environmentally friendly outboard? Who knows.

Have any doubts? Just read the beautiful gold decals on the front that say 4-Cycle! Notice the choke knob on the left and the speed control on the right.

This motor is basically a lawn mower engine mounted high-a-top an outboard lower unit.  It has two tubes that lead from the power-head down to the lower unit.  One encloses the drive shaft, the other is for the exhaust…both are of high grade brass…as this motor was touted for use in salt water.

Starboard side.

The top mounted tank looks massive, but in fact is fairly small-ish as it has many recesses to allow for air flow and cooling of the power-head.  The tank and lower shrouds act as baffles to keep air flowing around this motor for cooling as there is no impeller.  Yup.  It is totally air-cooled!  Pretty sweet!

Being a 4-stroke motor, oil is provided from an oil sump on the motor block. The manufacturer labled the fuel cap to remind the owner mixing oil is not necessary as it is with 2-stroke outboards.

The lower unit is very basic like most "kicker motors" of this horsepower from the day.

This motor has no neutral or reverse, but some later Lauson outboards did have that feature added.  Most were problematic and finicky.

The power-head is removed from the "leg" for servicing. It really is basically an lawn mower engine. Get a load of the fins on the flywheel that bring cool air into the heavy aluminum shroud that surround the motor.

A simple rope sheave is used to pull-start this Lauson. Some later models had a recoil type starter.

A simple, but reliable Tillotson carburator is feeds the fuel into this motor.

The brass tube that encases the driveshaft has been given a cursory buffing, and may get a polishing and clear-coat to "spice-up" this motor a bit. The flange at the left is where the motor attaches. It looks like a pipe flange with about 8 bolts to hold things together.

The exhaust and driveshaft tubes come together at the top of the lower unit. Since there is no forward, reverse or neutral, this lower unit is very simple and uses gear lube such as Lubriplate 105.

 This motor will get a fresh coat of silver hammer-tone paint, new decals, probably polished and clear-coated exhaust and drive shaft tubes, then she’ll be good as new.  I kind of look forward to seeing how many looks she gets as I putt along making the same noise most people on the water are trying to forget.  The sound of a LAWNMOWER!