As fossil fuels are depleting gradually with the course of time there is a need for developing innovative products that can extract maximum potential that the system can deliver. One of the key areas that still make use of diesel fuels for experiencing thermal comfort is the boat heating system. Due to its user-friendly characteristics with low maintenance requirements, space heater has still be the benchmark for all other types of heaters. The boat cabin heater is an essential setup for all kinds of boats and ships not just for the warmth but also to eliminate the dampness that can spread throughout the boat in cold weather. The paper presents a detailed analysis of thermal behaviour inside a space heater using computational fluid dynamics technique to study the effect of fin numbers and fin location inside the heat exchanger. A total of 11 cases were simulated to study the effect of a fin on the heat transfer rate and pressure drop. An optimisation is done to have maximum heat transfer rate with minimum pressure drop and results showed that case number 9 has satisfied the above criteria to obtain an effectiveness of 90%. © 2017 Informa UK Limited, trading as Taylor & Francis Group.