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Old 27-01-2021, 07:27   #1
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Who makes the shortest 9.9 outboard?

I'm trying to make an outboard mount in a cockpit locker, but my old outboard is too tall, and due for upgrade anyways.

Who makes the shortest, from skeg to engine cover, 9.9 range outboard?
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Old 28-01-2021, 14:18   #2
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Re: Who makes the shortest 9.9 outboard?

May be just me, but I wouldn't think this is the sort of information normally held by most folks here. Not for all motors out there.

I'd just get specs from the manufacturers to compare, but that might exclude older motors.
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Old 28-01-2021, 14:40   #3
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Re: Who makes the shortest 9.9 outboard?

I was under the impression they were all pretty standard at either 15" or 20" shafts. I've seen longer than 20" shafts, but I've never seen shorter than 15".

Then again, I've never seen a Dodo bird or a dinosaur, but that doesn't mean they didn't exist at one time.
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Old 28-01-2021, 15:03   #4
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Re: Who makes the shortest 9.9 outboard?

FYI:

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.

Primer:

Shaft length:

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
common.
Slower boats like work boats or displacement hulls need the
prop to be lower not only for better "bite" in the water but to
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
transom motor 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 filters.
This is so clear that the USCG and ABYC penalize a low-cut transom in their capacity calculation formulas.

Reference: https://boatbuildercentral.com/suppo...d-transoms.pdf
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Old 29-01-2021, 19:39   #5
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Re: Who makes the shortest 9.9 outboard?

Well, his question isn't without merit...mainly because one motor might be taller with respect to the mounting bracket than another. This was particularly true in larger motors where Mercury made, for example, tall, thin inline 4 cylinder motors and OMC sold a shorter, wider V4 motor in that size. In the size he's talking about there may be (doubtful) a shorter 1 cylinder motor. I don't think shaft lengths are that precise or uniform. (Honda makes some odd shaft lengths, too) He may be looking for only an inch or less.

I just don't think that body of knowledge about all motors would or should be here.
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Old 29-01-2021, 20:36   #6
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Re: Who makes the shortest 9.9 outboard?

There are three key segments of an outboard motor.

1) The power head
2) The mid section [which is essentially the shaft between the transom clamp and the anti ventilation plate, a.k.a. incorrectly as the cavitation plate]
3) The lower unit.

The shaft length is the variable component for a outboard motor and is the part whose length is selected so as to allow the proper depth of placement into the water. Determine the proper length of this section, then seek out a motor to fit that length. If that is too long for your storage compartment then either make the storage compartment longer or determine if you can lower the transom, but never lower the transom below a safe distance above the water surface for the specific design of your vessel.
With a displacement boat [such as a sailboat] the anti ventilation plate should be placed lower than the bottom of the hull, further below the water surface as was discussed in my earlier post.


Reference the images below for guidance.

Enjoy your new motor and boating.
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Old 29-01-2021, 20:52   #7
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Re: Who makes the shortest 9.9 outboard?

Tohatsu's 9.9 is EFI equipped and also comes with a high thrust four blade version which is awesome for sailboating with its high torque and slow speed capacity. The SailPro is my favorite by far but I have the long shaft so as to keep the propeller in the water when the boat hobby horses in waves.
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