Propulsion Equipment · Shaft Line & Propulsion
The Twin Disc MG-5170 DC is a marine transmission (gearbox) with six reduction ratios, from 4.06 to 6.95 to 1. Its maximum rating is 578 kW (775 hp) at 2100 rpm in intermediate duty. With the 4.06, 4.50, 5.03 or 5.95 ratio the input rating is 507 kW (680 hp) for continuous duty and 537 kW (720 hp) for medium duty, both at 1800 rpm, and 578 kW (775 hp) for intermediate duty at 2100 rpm. The 6.53 and 6.95 ratios are rated lower, at 459 kW (615 hp) for both continuous and medium duty at 1800 rpm and 545 kW (731 hp) for intermediate duty at 2100 rpm. All ratings assume a standard right-hand rotation engine; maximum rated input speed is 2500 rpm and minimum engine low idle speed is 450 rpm.
Dry weight with the alloy housing is 850 kg. Standard fit starts with a torsional input coupling (14 or 18 inch) with torsional stop and also covers an oil pressure gauge, rpm pickup ports, an oil strainer with filter and SAE housings no. 1 and 0. Options include a companion flange, an electric selector valve for 12 V or 24 V, mounting brackets, an oil temperature gauge, raw-water or fresh-water heat exchangers, a remote-mounted filter, a trolling valve and power take-offs. Live PTO drives are quoted at 592 N m (437 lb-ft) for SAE C and 1186 N m (875 lb-ft) for SAE C-C, and the same values apply with a hydraulic disconnect clutch.
Twin Disc's intermediate duty class allows up to 3000 hours a year for models larger than the MG-5114 Series, with half of the running time at full engine rating; named uses include ferries, some displacement hull yachts and certain bow and stern thruster drives. Medium duty means up to 4000 hours a year with up to 80 % of the time at full power, for vessels such as mid-water trawlers, crew and supply boats and ferries. Continuous duty suits steady operation, for example fishing trawlers, tugs and ocean-going vessels. Torsional compatibility of the drive line is the responsibility of the assembler, and a mismatch can cause gear clatter at low speeds or damage to drive train parts.
Sources: Twin Disc datasheet MG-5170, checked 05.10.2026
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