The total cost of installation has dropped regularly in the last decade, which to some politicians reduces the need for government incentives. (solar-estimate.org)
However, the ease - of - manoeuvring a two stroke engine is less than that of a four stroke engine and the initial cost of installation of a two stroke propulsion plant is also much higher than running and maintenance cost of a 4 stroke engine. (marineinsight.com)
From an environmental point of view it is clearly positive but the whole operation comes with quite a high cost of installation which at this point is still the main reason why this technology hasn't spread further. (treehugger.com)