A determination to secure small-ship propulsion business led in 1991 to the introduction of a 330 mm bore/1050 mm stroke LSII design (Figure 11.3). The series succeeded the 370 mm bore LA models which pioneered the modern 'mini-bore' two-stroke engine from the late 1970s for small general cargo tonnage, tankers, colliers, feeder containerships and even large fishing vessels. The longer stroke and more advanced UEC 33LSII engine now develops 566 kW/cylinder at 215 rev/min and covers an output band from 1230 kW to 4530 kW at 162-215 rev/min with four- to eight-cylinder models.

Monoblock exh.

gas receiver Exh. gas diffuser Hydraulically actuated

Monoblock exh.

gas receiver Exh. gas diffuser Hydraulically actuated

Figure 11.3 Construction of UEC 33LSII engine

Mitsubishi enhanced its medium power programme in 1992 by upgrading the 500 mm and 600 mm bore models to LSII status. Later power upratings of 3-5 per cent for these UEC50LSII/60LSII models, without major design changes, were introduced to meet the demands of larger ships and higher service speeds. The specific outputs respectively rose to 1445 kW and 2045 kW per cylinder. With a stroke/ bore ratio of 3.9:1, the 50LSII series embraces four-to-eight-cylinder versions covering an output range up to 11 560 kW at 127 rev/min.

The small bore programme was strengthened in 1995 with 370 mm and 430 mm UEC LSII designs to attract business from handy-sized bulk carriers, feeder containerships, small tankers and gas carriers. The engines plugged a gap between the established 330 mm and 500 mm bore LSII series. The UEC 37LSII engine offers an output of 772 kW/cylinder at 186 rev/min from five-to-eight-cylinder versions, while the UEC 43LSII engine delivers 1050 kW/cylinder at 160 rev/min from four-to-eight-cylinder models. The first UEC 37LSII engine, a six-cylinder model, completed testing in early 2000, and the debut order for a 43LSII engine, a seven-cylinder model, was logged in 2002.

UEC37LSII engine data


370 mm


1290 mm

Stroke/bore ratio

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