SERVICE CLASSIFICATION DEFINITIONS
Up to 500 hours/year, low load factor usage planing hull vessels where typical full
engine throttle operation is less than 10% of total time. The balance of operation
at 80% of full engine throttle or less. Marine transmissions for use in long range
pleasure cruisers, sportfish charter boats/patrol boats do not qualify for Pleasure
Craft Service. Note: Some revenue producing applications such as Planing Hull Bristol
Bay Gillnetter do qualify under Pleasure Craft rating definition.
Relatively low hour usage (less than 1500 hours/year) where full throttle operation
is 2 hours out of 12. Typical applications include planing hull vessels such as
fire boats, sportfish charter boats, and patrol/customs boats. This rating is also
applicable to some bow and stern thruster applications.
Hour usage of up to 2000 hours/year (for models MG-5114 and smaller) and up to 3000
hours/year (for models larger than MG-5114) with 50% of the operating time at full
engine rating. Typical applications include planing hull vessels such as ferries,
fishing boats, some crew boats, and also some displacement hull yachts as well as
some bow and stern thruster applications.
Hour usage of up to 4000 hours/year with up to 80% of operating time at full engine
power. This duty classification is for usage where some variations in engine speed/power
occur as part of normal vessel operation. Typical vessels include mid-water trawlers,
crew/supply boats, ferries, and some inland water tow boats.
For use in continuous operation with little or no variation in engine speed/power
settings. Typical vessels include fishing trawlers, tow/tug boats and ocean going
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IMPORTANT APPLICATION INFORMATION
- Transmission ratings are based on use of the transmission in a torsionally compatible
system utilizing a suitable input torsional coupling.
- Ratings are for diesel engines at the indicated speeds, unless otherwise indicated.
- Ratings are shown in SAE horsepower (HP).
- Consult factory for ratings applicable to gasoline engines, gas turbines, or other
applications not conforming to the given service class definitions.
- Ratings apply to right hand engines (i.e., counter-clockwise flywheel rotation when
viewing rear of engine).
- Ratings are full power forward or reverse except where specified by "F" (using forward
gear train for forward).
- Transmission ratings should equal or exceed the engine's published ratings for the
- Final marine transmission selections are to be confirmed prior to issuance of the
purchase order. For unusual or unique applications, please contact Twin Disc, Inc.
for product selection assistance.
- Marine transmission input couplings provided by Twin Disc are configured to interface
with engine flywheels which conform to SAE J620 standards. Please consult Twin Disc
when use of non-standard flywheels are contemplated.
- Most of the transmissions listed herein are to be mounted directly on the SAE flywheel
housing of the engine. It is necessary that the engine crankshaft end-play be measured
before the driven equipment is installed and rechecked after the driven equipment
is installed. The endplay measurements, before and after transmission installation,
should be the same. If not the same, the driven equipment should be removed and
the problem source located and corrected before the engine is started. Engine crankshaft
endplay measurement is considered mandatory.
- The given data is subject to modifications/corrections without prior notice.
- Use certified print for installation.
Disregarding propulsion system torsional compatibility could cause damage to components
in the drive train resulting in loss of mobility. At minimum, system incompatibility
could result in gear clatter at low speeds.
The responsibility for ensuring that the torsional compatibility of the propulsion
system is satisfactory rests with the assembler of the drive and driven equipment.
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