BBC Boards |
|The majority of the
definitions are courtesy of Scream
I've left out a few that don't relate to bassboats and added a few
definitions of my own.
Plate: (Also referred to as Cavitation Plate).
The horizontal plate above the lower unit. It is intended to
prevent the prop from sucking surface air, ventilating into it and
causing a cavitation-like effect. More useful on a deeply mounted
outboard; on a high-performance or surfacing setups, it is of limited
value due to it being out of the water while on plane.
Blowout: This can occur when the ratio of air to water
around the propeller gets so high that the prop is no longer grabbing
water, but is trying to propel itself through air (or a relative
vacuum). This causes the prop to lose "bite" and then a
chain of events occurs that can range from merely a "loose"
steering feeling to a violent turn to the right (typically). The
speed at which this occurs varies with boat design and propeller design.
Blueprinting: (or blueprint) On an engine, it is bringing the
specifications to a tighter tolerance range. On a hull, it is the process
of making the bottom straight for the entire running surfaces and
bringing any edges to a sharp edge, especially the hull/transom
interface. Check with the boat manufacturer before removing hooks
and rockers that may have been designed into the hull for a purpose.
Cavitation: The formation of "voids" or air
inside the water stream, caused by low pressure near a surface.
Encountered when the water separates from the propeller. Also
called "ventilation", can cause propeller burn and can lead to
Cavitation Burn: Metal erosion on the propeller blades
caused by air or gaseous bubbles on the positive side of the propeller
blades. Usually caused by excessive ventilation of the propeller.
Center Steer: A hull setup that positions the steering helm
(and driver) in the center of the boat, laterally.
Chine Walk: Severe side-to-side rolling of the boat. It
actually means to roll from chine to chine but it is also used for less
severe rolling, although always severe enough to scare or cause a loss
of control. Essentially, this is a characteristic of high speed V-bottom boats, where the boat is balancing on the pad or very bottom,
further aggravated by the drag of the lower unit.
Chinewalking must be compensated for by steering input from the driver.
Note: As a general rule, a
properly setup bass boat will chinewalk less than one that has not been
CLE: "Crescent Leading Edge" lower unit. An
older generation Mercury high performance lower unit with integral
nosecone and low water pickups. There were two designs of the CLE,
both offering the same performance. Designed for high speed
surfacing applications, and originally equipped on 2.4 Bridgeport
engines. No longer in production.
Cleaver Prop: A stern lifting propeller design utilizing
thin leading edges and square trailing edges, primarily for stern lift
& tunnel boats.
Cone: (see Nosecone)
Crossflow: A type of two-stroke technology. The
incoming fuel mixture is deflected by a dam on the piston and is forced
up into the combustion chamber.
Cup: Modified area of the trailing edge of the propeller
that will and can affect holeshot and bow lift.
Dual Cable Steering: Safety item. Two steering cables
that offer redundancy if one cable should fail. They are also used
to eliminate excess slack in the steering system, offering greater
control. The cables can attach to the engine from the same side or
Detonation: Internal deterioration of aluminum components
(usually the piston) resulting from lean mixtures, the collision of
multiple flame fronts (excessive timing advance) and poor quality fuel.
ECU: Electronic Control Unit - the "brains" of an
electronic fuel injection system. A computer that monitors engine
systems and controls fuel delivery.
Gauge: An instrument for monitoring information - speed,
engine rpm, water pressure etc.
Galling: Occurs when the threads of a bolt are damaged from
lack of lubrication or excessive force of tightening. This is not
Gelcoat: The outer cosmetic layer of a fiberglass hull that
provides a protective, high-luster finish. Similar to paint, but epoxy-based and much thicker.
Holeshot: How the boat performs from a dead stop to planing
speed. Generally, a faster holeshot is more desirable.
Hook: (noun) The shape of the hull where the bottom is
concave; rather than at or near the transom. (A 'hook' at the very
edge of the transom may be part of the hull design.)
Opposite of a R. A hook can be caused by insufficient support from the
of the hull or actually designed into the hull by the
Hook: (verb) The tendency of some hulls to dart to
the right or left due to drastic weight transfer to the bow, usually
under extreme deceleration. Also can be noticed in tight turns
when one side of the hull wets out.
HP: (horsepower) The power output of an engine or
Computed by using the following formula: Torque x RPM /
Hydrodynamics: Pertains to the properties and forces of the
flow of water over or around a surface.
Hydraulic Steering: A steering system that utilizes fluid
pressure to assist in steering action.
The system is comprised of a fluid pump, pressure lines and the steering
Jackplate: Also known as a transom jack or lift
plate. A mechanism that allows vertical adjustment of the outboard
on the transom. It also adds setback. There are manual and
Kill Switch: Emergency cut-off switch, usually actuated by
a lanyard attached to the driver.
When pulled, the lanyard will actuate the switch, cutting the engine and
Kite: (verb) The affect on a boat when too much air is
packed under it at high speed; usually due to an inherent dynamic
instability in high speed powerboats. Caused by excessive trim,
gusts of wind or launching off a wave. Many times can cause a 'blowover'.
Layup: Referring to the application layers, thickness and
materials used in the construction of a fiberglass hull.
Lean (Lean Mixture): A lower than normal fuel content in
the engine's air-fuel mix. Often results in higher operating
temperatures, overheating, detonation, and increased power output.
Looper or Loop Charged: Another type of two-stroke
technology, different from the Crossflow. The fuel mixture
enters the cylinder on opposite sides and when it hits in the
it is forced up into the combustion chamber.
Low Water Pickups: Cooling water inlets on a lower
unit. These are on the nose, (or bullet) and are usually below the
point. Allows for high motor height and still deliver sufficient
water for cooling. The normal location of the water pickup for the
water pump is on the sides of the lower unit above the gearcase.
Midsection: The part of an outboard than connects the lower
unit and the powerhead together.
Contains the steering mechanisms as well as the tilt/trim mechanisms.
Opposed Steering: The steering cables attached to the
outboard from the starboard and port sides.
Nose(or Cone): The foremost part of the gearcase on a
lower unit. It is also the aftermarket 'add-on' to create a longer
aspect ratio of the gearcase. It is the location for the
water pickups. As a general rule, an aftermarket nosecone is only
beneficial to bass boats running 80+ mph. On slower boats, adding a
nosecone could actually slow the boat down.
Pad: The flat, center component of a V-bottom hull.
Pads offer V-bottom hulls greater lift compared to non-padded V-bottom
designs. (Also refers to the running surfaces of the outboard
sponsons on a tunnel boat.)
Planing: When the boat has achieved sufficient speed to
ride onto its bow wave, a function of the hydrodynamic design of the
hull. Phase of operation that comes after "submerged"
motion, has characteristics of significantly less drag.
Pitch: (Propeller) The theoretical distance a propeller
travels in one full rotation.
For example, with a 25" pitch prop, the prop will "screw"
through the water 25" in one full rotation. This is theoretical due
to a certain amount of slippage being present.
Porpoising: A constant rhythmic front to back pitching
action of the boat, caused by a dynamic longitudinal instability.
Often results from improper dynamic balance of weight and aero/hydro-dynamic forces, and usually occurs at specific speed for a
unique hull setup.
Over trimming the engine might cause this, whereby the bow is held up by
prop thrust, but not enough to stabilize the condition. (The boat
will rise because of the prop thrust, the weight of the bow will drop it
down, the prop will raise it again, etc.,etc.) Trimming down (in)
can eliminate it at low speeds. The same action from the boat
caused by not enough hull lift and subsequent falling of the bow back
into the water.
Powerhead: The actual engine itself.
Prop Shaft: The output shaft of the lower unit where the
propeller is mounted.
Prop Shaft Centerline: Referenced to the boat bottom (pad)
for prop height measurement.
Measured at zero trim with the cavitation plate parallel with the bottom of
Can be measured with a straight edge placed on the pad; the distance
between the center of the prop shaft (point of the bullet of the
gearcase), and the straight edge is then measured, and this is the
distance that you are below (or above on certain high performance
hulls), the pad.
Prop Walk: A "paddle wheel" effect whereby the
propeller will 'walk' across the water, sometimes caused by excessive
engine height, not enough compensating angle in the torque tab and
high-rake propellers. Often occurs with 3 blade propellers less
than with 4-5 blades.
Rake (propeller): The longitudinal angle of the
propeller blades. Usually, high rake props provide more bow lift
and better holding power. Rake and pitch are not always related.
Rich (Rich Mixture): A higher than normal fuel content in
the engine's air/fuel mix.
Often results in cooler operating temperatures, black exhaust deposits
(carbon), plug fouling and decreased power output.
Rig: (noun) The trailer and boat package as towed.
Also used to refer to the boat/engine combination.
Rig: (verb) To install anything not part of the hull
manufacture process. Interior, gauges, wiring, engine, so on, to
ready the boat for operation.
Rocker: The shape of the hull where, rather than being flat
it takes on a convex shape.
Opposite of Hook. Can be caused by insufficient support
from the trailer or failure of the hull.
Almost never an intentional design characteristic of the hull.
RPM: "Revolutions Per Minute". Almost
always referring to engine crankshaft rotation speed.
Safety Switch: Safety Item. See Kill Switch.
Setback: The distance between the transom and the
outboard. Changes the center of gravity of the boat and allows the
propeller to operate in less aerated water.
Setup: Everything in the boat that contributes to the
performance required. A setup can be geared towards top speed,
holeshot, midrange or a compromise of the three.
Usually referring to how a bassboat is setup, whether it has a
jackplate, the engine height, prop being used, etc.
Skeg: Lower rudder-like component of the gearcase. It is
the lowest part of the motor.
Provides stability and tracking as well as counteracting steering torque
when equipped with a Torque Tab. (Also provides some protection
for the propeller.)
Splines: Machined grooves on a driveshaft, propeller shaft
or some other shaft that locks its mating counterpart in place,
preventing rotation on the shaft.
Solid Engine Mounts: Safety and performance item.
Solid aluminum or plastic composite, rather than rubber engine
mounts. Reduces slack in engine mount system, offering greater
control and stability. (For certain setups solid mounts can reduce
Sportmaster: Current generation Mercury high performance
lower unit. Includes a nosecone and low water pickups into the
design, as well as stronger than stock internals.
Designed for high speed surfacing applications. Available for
2.0/2.4/2.5 and 3.0 liter applications.
Stator: Wire winding assembly, usually located under the
flywheel of an outboard engine.
Generates electricity for the ignition and charging system as the
flywheel's magnets pass over the windings.
Stringers: The "backbone" of a bassboat to
provide it with its strength. Many are wood stringers encapsulated
in fiberglass, others are made of composite materials. (Simply put,
stringers are the "skeleton" of the structure and are between
the floor and the hull.)
Stuffing: The opposite of Kite. A serious
situation that occurs when the bow digs into a wave and the water
pressure drives the bow down, in many cases causing severe damage and
Tongue: The part of the trailer that continues forward to
connect to the hitch ball.
Weight of the trailer tongue should be approximately 10% of the entire
rig weight as measured
at the hitch connection. (Too light a tongue weight will usually cause
swaying of the trailer and generally poor towing characteristics.)
Torquemaster: A heavy duty high performance Mercury lower
unit that does not have a nosecone. Designed for boats with
heavier loads that require power trim for bow lift.
Current models include low water pickups, however earlier models did
not. Available for 2.5 and 3.0L applications.
Tilt: The mechanism that lifts the outboard past the
supports - out of the range of Trim.
May or may not be the same mechanism as trim.
Transom: The back of the boat. Usually concerning the
attachment area for the outboard or the jackplate.
Transom wedges: Shims placed in between the outboard and
the transom or jackplate that change the effective trim angles.
Trim: The angle of thrust from the propeller. The
trim angle can be adjusted in (negative) or out (positive). Zero
trim is when the propshaft is parallel with the boat bottom.
Positive trim helps lift the bow, negative trim holds the bow down.
Trim Pump: Electric pumping unit that pressurizes the
engine hydraulic trim system.
Tuner: The megaphone-shaped exhaust pipes inside the
midsection. Essentially, the tuner is the exhaust
"header" of the outboard engine.
V-Bottom: Hull design utilizing a centrally located, single
running surface for lift.
These hull designs generally do not rely on air pressure for a
significant portion of their lift.
Wheel Torque: The tendency for the steering wheel to
forcibly turn right. Caused by the prop rotation and increases as
the engine is jacked higher out of the water, becoming maximum when only
one blade of the prop is entering the water.
WOT: Wide Open Throttle.