Re: Mercury Mark 55A vs Mercury Mark 400

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June 17, 2015 at 3:15 pm #18272
chinewalker
Participant

    US Member

    Actually, the 1959 Mark 55A is a 45 cube motor, too. The big difference is in the carbs – the 55A has smaller bore AJ series carbs, while the 400 has bigger KA series carbs. Plus, the crankcase is machined differently to accommodate the different carbs…