Pleasure Craft - Up to 500 hours/year, low load factor usage planning 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.
Light Duty - Relatively low usage (less than 1500 hours/year) where full throttle operation is two hours out of 12. Typical applications include planning hull vessels such as fire boats, sport-fish charter boats, and patrol/customs boats. The rating is also applicable to some bow stern thruster applications.
Intermediate Duty - Hours usage up to 2000 hours/year with 50% of the operating time at full engine rating. Typical applications include planning hull vessels such as ferries, fishing boats, some crew boats and some displacement hull yachts as well as some bow and stern thrusters application.
Medium Duty - Hours usage up to 4000 hours/year with up to 80% of operating time at full engine power. This classification is for usage where some variations in engine speed/power occur as part of normal vessel operation. This includes 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. This includes fishing trawlers, tow/tug boats and ocean going vessels.


From mid-size and large diesel-powered pleasure craft to a myriad of commercial boat applications, Twin Disc has marine transmission systems that precisely fit the horsepower and operating needs of each.

It feature healical gearing for quieter operation; bydraulic-controlled and oil-cooled clutches for smooth, fast shifting; identical reduction ratiosin forward and reverse, in most cases full power forward and reverse, and minimal external plumbing.

Some models are available with down-angle output to provide near-level engine installation, a feature of particular interest to boat builders for optimizing space within the vessel.