Designing Outboard Bracket

I’ve made a decision:  Shackleton will have a motor. Sailing in Idaho has taught me a few things.  At times, the wind will just suddenly disappear or die down significantly.  Other times, it will build to gale force with no warning.  I don’t want to drive 2 hours to a mountain lake, only to find no wind.  With a motor, I can still cruise around the lake and look things over.  I believe it makes Scamp a more versatile boat.

Motor Criteria: I was looking for the following things in an outboard:

  1. Very small Displacement (2.3 – 2.5 h.p.)
  2. Lightweight (30 lb. dry weight or less if I could find it)
  3. Quiet (this was a struck against the Honda…said to be noisier than liquid cooled outboards)
  4. Reliable (I wanted a new outboard for Shackleton)
  5. Smooth Running (I prefer liquid cooled engines)

(Drum roll please)

Which motor did I choose? I selected the Suzuki 2.5 hp outboard.  According to manufacture specs, this motor is as light as the Honda 2.3 hp outboard (Suzuki 29 lb. vs Honda 29.5 lb.).  All other outboards I researched were significantly heavier than the Honda and Suzuki.  The liquid cooled Suzuki is said to be quieter than the Honda, and offers more torque at similar RPM (according to an internet article I read).   The quiet factor is a big deal to me.  I wanted the quietest motor possible, without going to electric (I already maintain far too many batteries in my life).  The Suzuki has a gear box, allowing me to warm-up the engine in neutral (without the prop turning) before shifting into forward.  This may prove handy for Spring and Fall cold weather sailing.  Online dealers offer free shipping; $709 put the motor on my doorstep. DSC00001Here you see my beautiful Suzuki outboard mounted to an adjustable Trac Aluminum outboard bracket (model #T10050).  As I mounted this motor to a scrap piece of plywood, I became immediately aware of several problems.   DSC00002 First, notice the bracket handle strikes the mock transom, preventing the bracket from being raising to it’s top most position.   DSC00004Second, notice the minimal off-set of the motor in the up position.  The high transom found on Scamp, prevents the motor from being tilted completely forward.  So, I can’t raise the motor all the way up and I can’t tilt the motor forward to get the prop out of the water when sailing.

What now?  After some thought, I had the perfect answer.  Build a shim, moving the outboard away from the transom, solving my problems.  First, I tried a 3″ shim, then 4″, then 5″.  Here’s what I learned:  5″ does provide good access to the motor handle and allows the bracket to easily raise all the way up but the motor still won’t tilt forward far enough to engage the motor tilt catch.  Very disappointing.  It’s also overly complicated for the requirements at hand.  This is a small motor.  This is a light motor.  The outboard bracket is beyond the needs of this motor.  And, it doesn’t work in this application.  I wanted a more practical, simpler solution.

Hum…this just isn’t working for me or Shackleton (the boat’s spirit whispers to me occasionally).   After staring at things for a few hours, I noticed that the Suzuki motor (given enough room) will tilt almost a full 90 degrees forward.  With this amount of forward tilt, a stationary bracket would allow me to raise the motor entirely out of the water for sailing.  A stationary bracket would also be much simpler.  No moving parts, no springs, no lubrication points to maintain.  Nothing to raise or lower.  I liked where this was going.  

In looking at online fixed brackets, however, none of them offer enough off-set to allow the motor to tilt forward.  In the end, I decided to design and build my own outboard bracket.DSC00001With paper and pen, I started playing with design ideas. DSC00012 I wanted the bracket to be strong, simple and light, while allowing full forward tilting movement of the motor.DSC00016DSC00008I also wanted to recess the motor mounting screws into the wood for a migration free clamping surface.  DSC00010DSC00014I tried to lighten up all the parts without compromising strength.  My Ridgid sander smoothed out all my rough cuts.  I also ran a 1/4″ round-over bit over all exposed edges. DSC00018One coat of epoxy on all the parts.

My outboard motor bracket parts (from Left to Right).  

  1. Back block (V.G. Douglas Fir).  This will be mounted directly to the transom.  The bracket sides will screw and glue to this block.  It measures 6 1/2″ wide, 10″ tall and 1 1/4″ thick.   I cut out the center to lighten it up.
  2. Front block (V.G. Douglas Fir.)  The back side of this block has the recessed motor screw holes.  It measures 6 1/2″ wide, 5 1/2″ tall and 1 3/4″ thick.
  3. Bracket sides (3/4″ Baltic Birch).  Centers cut out to reduce weight.  The measurements can be seen in a photo above.DSC00039 DSC00037 DSC00034 DSC00032The notch-out on the starboard side is to allow clearance for the motor choke knob.

 In mounting up the motor, things look really good.  A few observations:

  1. With the rudder down, the rudder is in front of the prop and cannot swing into the prop (I remember the sounds of chopping wood on my West Wight Potter 15).
  2. With the rudder up, the rudder is above the prop and can only swing into the motor shaft.
  3. With the motor tilted up, the prop will be completely out of the water.
  4. With the motor tilted up (and rudder fully up or down), the rudder can move freely without any contact whatsoever.
  5. The purchased motor bracket (that I will be returning) weighs 8.8 lb.
  6. The wooden motor mount I built weighs 6.25 lb.

I am very happy with this simple, wooden design.  I reduced weight aft (this may be offset, however, by the movement of the motor further aft), gained full tilting movement of the outboard, and prevented contact with the rudder. 

One step at a time, baby.

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3 thoughts on “Designing Outboard Bracket

  1. Brent –

    An elegant solution. Thanks for sharing.

    Remember on the tilt-up issue, the motor can be turned 90 degrees to usually allow more transom clearance. With my Torqeedo, max clearance comes at 180 degrees rotation of shaft, then I have a short lashing line I use to snug it up even further, beyond the limit of the tilt-up latch. That keeps the prop head well above the water, even when the boat is pitching quite a bit.

    See photo PB010002-1.jpg at http://smallcraftadvisor.com/message-board2/viewtopic.php?f=3&p=9616#p9616

  2. Hello, beautiful work. I’ve found this blog as I’m creating a mount for a Suzuki 2.5 for an inflatable.
    Much more utilitarian. Can you tell me the measurement between the two mounting screws? Center to center and total width from clamp left “pad” to right “pad”? Thanks in advance?

    • Charley,

      Thanks for the compliment. The overall bracket is 8″ wide & about 7 1/2″ tall on the mount/transom side of the bracket. Center to Center clamp pad is 3 1/2″, total clamp width is 5 1/4″ (outside edge of countersink hole to outside edge of countersink hole). Hope this helps.
      Brent

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