The International Maritime Organization (IMO) has introduced measures under its greenhouse gas (GHG) strategy to reduce CO₂ and other emissions from international shipping. These apply to both existing and newly built ships to support decarbonization of the global fleet until 2050. Since ships have a lifespan of over 20 years, a large share of the current fleet will stay in operation for years, and most are powered by traditional combustion engines. Order books also show that most newbuilds will continue to use conventional engines. Meeting IMO targets will therefore require large-scale retrofitting to enable the use of low or zero CO₂ marine fuels. This study addresses a gap in the maritime energy transition by evaluating the feasibility and economic implications of retrofitting marine engines to run on blended fuels. Several technical approaches are being explored to reduce conversion costs using fuel blends such as MDO or MGO combined with e-fuels to lower emissions. Methanol (CH₃OH) is emerging as a promising option due to its compatibility with existing engines and relatively low retrofitting costs. This paper explores the implications of using methanol for marine fuel insetting in ships with conventional engines. Initial tests show that up to 30% of fossil fuels can be replaced with methanol without compromising performance, while cutting CO₂ emissions significantly. The study follows a mixed-method approach including primary and secondary data, case studies, and expert interviews. Findings provide practical insight for shipowners, policymakers, and engine makers looking for short-term, scalable decarbonization solutions.