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!

15 Responses to “Bein’ Green: One of the original 4-stroke outboard motors…”

  1. 1 Chuck Sauber
    February 4, 2010 at 1:01 am

    They don’t sound much different than the 2 cycles as the underwater exhaust is quite effective as a muffler, but they idle slower, Chuck

  2. 3 Ron
    April 12, 2010 at 12:59 pm

    I got a motor just like this form my uncle ,, what are they worth? Are they somethign a collector might wnat?

    • 4 conductorjonz
      April 12, 2010 at 2:10 pm

      Hi Ron!

      A collector may desire these little motors, but they are not terribly valuable. Value will depend on your are, motor condition, fresh water or salt water use. I bought mine for 35 bucks at the local boatyard. It’s a novel little motor, well built, but at 2.5 hp not exactly a powerhouse. They also leak oil and grease and gas quite a bit. But that is the nature of “old motors”…and some new ones!

      Thanks for checking in!


  3. 5 psuggmog volbenz
    July 15, 2010 at 3:56 pm

    Hello, I have been using these little lausons since the early 1980s. I have a longshaft version and a short shaft one. The short shaft one has a steel exhaust tube instead of brass, supposedly an early production motor. I started the short shaft motor yesterday. It had been sitting in my shop for over twenty years since it’s last use. It started on the first pull!, all I had to do was claen the points. You mentioned new decals. Do you have a source for them? I would like to put new decals on my motors. The short shaft motor has olive drab paint under the silver. I wonder if any of these motor were used bu US armed forces during WWII.

  4. 7 Ed Sutherland
    August 18, 2010 at 11:49 am

    Are the tuneup specs available for this engine and if not, where can I find them. It was my understanding that this motor was a 3hp, not a 2.5hp . Is this possible?

  5. 9 Tizoc Gomez
    January 10, 2012 at 10:19 pm

    Hi there.

    I was wondering where you get the pain and decals for the 1950s Johnsons. I bought a 1954 wolverine with a 54 Johnson 25 and a 58 35hp that I would like to restore.

  6. 11 Chase
    August 16, 2013 at 11:49 am

    I’m currently restoring a Lauson S-351 3hp. They are really cool motors, but at this point I’m doing it for the joy of the restoration, not the value of the motor. Fully restored they go for about $350-450. Thanks for posting

  7. February 24, 2017 at 3:05 pm

    Lucky for all of us that (affordable) electric boat propulsion will soon be a reality with new battery chemistries and lower weights. While I love the sound of an old outboard (2 or 4-stroke, doesn’t matter), the noise and air/water pollution just isn’t responsible for a 21st century civilization.

    • 13 conductorjonz
      February 25, 2017 at 7:12 pm


      No electric motor is going to move any vessel…nor vehicle responsibly over the water any distance at a respectable speed for any length of time. I just don’t buy it.

      All these do gooder’s who think their Prius is going to save the planet are full of sheep dip! The damned battery will go bad eventually…and someday the goodies inside that battery will not be recylable…and thus end up buried inside Mother Earth’s crust.

      Its a nice dream…but electronics and water don’t go together well.

      Besides…if that was the answer…the Professor would have gotten the Minnow crew off the island long before the rescue. He had a way to make everything…including batteries.

      I’ll keep my old 2 cycle going until they pry it’s tiller from my cold dead hands.

      Thanks for checking in.

  8. 14 Ron Palmer
    November 28, 2017 at 3:49 pm

    Hello, I recently found a 40 to 47 Lauson outboard motor that looks identical to this one. The serial number is 7460. I cannot find any information on how to know what year the motor is. I am planning on restoring it. Do you have any way or anyone you can point me to who might know? Thanks in advance! Ron

    • 15 conductorjonz
      August 16, 2019 at 8:34 am

      They are nice little motors with many design flaw. Leaky oil gaskets and the cowl and fuel tank affect air flow for cooling, so not a good idea to run without those items.

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