Because you can! But it is not only. 4 stroke engines are used in marine applications as well. I think you need to ask the question a little bit more precise.

I have seen cars with dual cycle and lots of two wheelers. I think planes do as well.

What is it really you are after?

easier to maintain? but aren't lot of boats Diesel powered?

i asked that why dual cycle used in marine application? due to what specification of dual cycle it is used in it ? why it is not used in normal cars, bikes???????????

See you did not read my answer. I said there is or was cars and planes where the 2 stroke engine was used. So why so upset (at least it sounds like it) and not ask: where what when.

And why does the statement that diesel are commonly used not trigger something? I almost start to believe that pollution of the sea is the main reason of using 2 strokes in marine application.

I am out!

Many hand-held petrol-powered small appliances for outdoor use use the 2-stroke system. Though less efficient, the engines are simpler to construct, and simpler to maintain.

And less expensive in the market place. For an engine that may only see a few operating hours per year, first cost may be more important than overall operating efficiency.

What the H... is a "dual cycle" engine?

Is that a 2 stroke?

Two strokes make more power than a "same size" 4 stroke.

theoretically, they can produce twice power per cubic inch of diplacement because the cylinders compress and fire on every other stroke as opposed to a four cycle firing at every fourth stroke, making the engine ligher and cheaper to produce. they're dirty and would'nt pass an emission test for an auto. marine engines don't have to meet any pollution standard.

Modern two stroke, oil injected marine engines meet and surpass all current EPA criteria!

http://www.snowgoer.com/snowmobiling-features/why-2-stroke-direct-injection-is-a-big-deal/