MOTC Manual - edited

vibrations harmful to the engine. A propeller with worn blades will allow the engine
to accelerate beyond the recommended operating range which can result in damage
to the motor.
What to carry - It is recommended you carry a spare propeller, nut, locking device
(cotter pins or tab washers), thrust washers, and any other components that can fail
or be lost.
Other equipment to carry include: (a) adjustable wrench/prop tool (floating prop
wrenches are available), (b) a block of wood for setting between the propeller and
anti-ventilation plate when turning the prop nut, (c) spline grease.
Steps for removal inspection
Turn the engine and master switch off, remove the key and/or kill
switch, and set the gear shifter to neutral.
Straighten and remove the locking device (cotter pin or tab washer).
Place block of wood (e.g., 10” piece of two-by-four) between the anti-ventilation
plate and propeller blades to prevent rotation, and remove propeller nut.
Pull propeller straight off shaft, remove front thrust washer.
Remove any items wrapped around the prop and check for evidence of damage
to grease seal.
Coat propeller shaft with spline grease, wipe off extra and keep it clean.
Install front thrust washer, propeller, rear thrust hub, and propeller nut onto
shaft.
Replace propeller nut and tighten to manufacturer’s specification (e.g., 30 ft-lb).
As a rule-of-thumb, the propeller nut is tightened until “snug”. Secure propeller
nut to the shaft with the locking device (cotter pin or tab washer).
Propulsion Systems – Jet drive
Jet propulsion systems utilizing one
or more impellers (versus a
propellers) that pulls water up
through an intake positioned roughly
flush with the lowest part of the hull,
and shoots it out behind the boat.
Compared to prop-drives, jet drives
are less efficient. In addition,
accessing and removing an impeller
is more difficult, outboard jet drives
are louder than outboard prop drives,
jet pumps can get blocked by debris,
many jet drives (particularly on
outboards) respond sluggishly in
reverse, and because there is no skeg
or rudder, handling is comparably poor.
DOI – Motorboat Operator Certification Course Chapter 2 – 4