Adjusting Twin Engines; Max. Boat Speed Estimation - Yamaha F70AET Rigging Manual

MOUNTING THE OUTBOARD
MOTOR

ADJUSTING TWIN ENGINES

Set the engines in the toe-out position, and
measure the distances between the two
engines at the center point of the rear (a) and
front (b) of the lower casing. The difference
between measurement (a) and measurement
(b) should not exceed 25 mm (1 in.).
* Adjustment: (b) – (a) = Within 25 mm (1 in)
For best result, your toe-out distance should
be set so that the twin engines wake meets
approximately 7.5 – 15 m (25 – 50 ft) past the
stern of the boat.
7.5 – 15 m (25 – 50 ft)
(b)
(a)

MAX. BOAT SPEED ESTIMATION

Depending on the engine power, boat length
and boat weight, the maximum boat speed can
be generally estimated with the calculation for-
mula as below.
V = 1.398 L (PS/)
V = Estimated maximum boat speed (km/h)
L = Boat length (m)
PS = Prop shaft output power
= Displacement volume (ton)
For example:
Boat length = 8 m (27 ft)
Engine power = 250 ps
Displacement volume = 3 ton (3000 kg)
Max. boat speed [V] = 1.398
= 62.2 km/h (38.6 mph)
* This should be only used as a reference.
The maximum boat speed varies depending on
the hull design, rigging state, passengers weight,
engine weight, engine position, etc.
Confirm the actual boat speed by test run.
1-10
0.623
*water line
*water line
0.623
8 (250/3)