SERVICE CLASSIFICATION DEFINITIONS

Pleasure Craft

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.

Light Duty

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.

Intermediate Duty

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.

Medium Duty

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.

Continuous Duty

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 vessels.

back to top

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 given application.
• 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.

IMPORTANT NOTICE

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.

back to top