The methanol port injection with diesel ignition technology was tested on a marine methanol and diesel dual fuel engine. The study was focused on the combustion and thermal load for the combustion chamber between the methanol fuel mode and the diesel fuel mode. The test results show that the ignition delay is increased and combustion duration is decreased below 75% engine load in the methanol fuel mode. Meanwhile the exhaust temperature before turbine is also reduced in methanol mode. The temperature of the cylinder cover and liner is generally reduced in the methanol mode based on the measured temperature distribution of the cover and liner. But the temperature at parts of measured points varies greatly due to the combustion nonuniformity.