Most small horsepower outboards are made by Tohatsu which markets them under their own brand but also for private labeling to other major brands, meaning only the labeling and color may differ.
As to length, one can either adjust the transom height [e.g., raise it because obviously one can't lower it too much towards the waterline without taking on water] or purchase
the shaft length that is suitable for the craft.
The shaft length announced by the outboard manufacturer is the vertical distance between the inside of the clamp and the cavitation plate.
(We will not argue about names here but the proper name for the cavitation plate is anti ventilation plate).
Shaft lengths come in multiples of 5" (127 mm). Beware of names like short, long, normal shaft etc. Most will call a 15" standard, the 20" long shaft and 25" extra-long but boaters do not always agree on those names.
Use figures and measure your shaft please, no confusion is possible with figures.
Standard shaft lengths are 15, 20 and 25" (38, 50 and 63 cm). Those shaft lengths are an industry standard but there are exceptions. For mid-range engines, the most common shaft length is 20" (508 mm). 15" shafts should
be reserved to protected waters. 25" shaft are rare below 100 HP. Other shaft lengths exist.
Many small engines, 10HP or less have shafts around 17.5" long
(45 cm). Outboards sold
for sailboat propulsion
often have an
unusual long shaft for their size. Very large engines, 250 HP or
more, can have 30" long shafts. (from here, I switch to inches
only as units. 1" = 2.5 cm).
Select the correct shaft length:
When selecting a shaft length, we must start with the location
of the prop or more exactly, the height of the cavitation plate.
From there, we will know which type of shaft length to install or,
if we build/modify the boat
, decide how high the transom
clamping board will be.
Most planing boats will work
better with the cavitation plate
flush with the bottom of the boat
or a little bit above: 1/2" is
Slower boats like work
boats or displacement
hulls need the
prop to be lower not only for better "bite" in the water
avoid aeration when the boat pitches (hobby horse.) The
cavitation plate of a small dinghy
outboard is often 2 or 3"
below the bottom. Same for sailboats auxiliary outboards
and most other displacement
hulls. This creates a little more
drag but that is almost irrelevant at those speeds.
It is unsafe to
have the engine
block too close to the water
on a low transom. Plus,
a low transom cut is an invitation for the water to flood the boat. There
are many reported cases of boats that sunk flooded through the
well cut. The boat can be swamped by its own wake
when coming off plane or going in reverse. If the engine needs service
at sea, the block will be exposed to the water especially with some
crew members all standing in the stern arguing about spark plugs and fuel
This is so clear that the USCG and ABYC penalize a low-cut transom in their capacity calculation formulas.