Tugboat Maneuvering — Chapter 7

Maneuvering Using Vessel
Inertia & Forward Momentum

Due to the tugboat's specialized hull shape and propulsion system, vessel behavior differs greatly from conventional ships. This guide covers techniques for utilizing inertia and momentum — from deceleration to course changes and berthing.

Page 7-1

1. Basic Operations — Deceleration & Stop

Full Ahead → Half Ahead → Neutral with RPM increase for braking. Kort Nozzle + Z-Peller braking effect.

Deceleration Sequence
PHASE
SPEED
10.0
KNOTS

⚓ KORT NOZZLE + Z-PELLER SYSTEM

At 3+ Knots forward/astern, raising both RPMs at NEUTRAL lever → propeller thrust creates BRAKING effect → vessel stops rapidly.

Page 7-2

2. Port/Starboard Course Change Using Forward Momentum

Differential RPM: Higher port RPM → port turn; higher stbd RPM → stbd turn. Steering at neutral.

Course Change
STEP
SPEED
10.0
KNOTS

⚠ CRITICAL WARNING

Above 5 Knots: Reduce both RPMs FIRST, then steering to neutral. Sudden NEUTRAL → severe vibration → SYSTEM FAILURE.

Page 7-3

3. Port Turn Using Forward Momentum

Gradual port turn by slightly increasing port engine RPM while coasting on momentum.

Port Turn
STEP
SPEED
10.0
KNOTS

⚠ CRITICAL WARNING

Above 5 Knots: Reduce RPMs FIRST, then steering neutral.

Page 7-4

4. Port Turn Berthing — Starboard Side Alongside

Forward momentum drives a wide port turn arc ~180°. Vessel berths stbd-side-to with astern braking.

Port Turn → Stbd Side Berthing
PIER — QUAY WALL
STEP
SPEED
10.0
KNOTS
Page 7-5

5. Starboard Turn Berthing — Port Side Alongside

Forward momentum drives a wide stbd turn arc ~180°. Vessel berths port-side-to with astern braking.

Stbd Turn → Port Side Berthing
PIER — QUAY WALL
STEP
SPEED
10.0
KNOTS