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Message: <blockquote data-quote="DaleH" data-source="post: 495612" data-attributes="member: 15636">Not sure, but more HP is typically better than not. Also buy the Tohatsu if a Dealer is near you, as they make all the small outboards for Mercury.Or check the schematics online at marineengine.com and see if there is a “restrictor plate” put in behind the carb to the throttle body. If so remove it and if the block on the 2.5 is the same size as that on the 3.5, removing it from the 2.5 would turn your motor into a 3.5hp.FWIW I just went looking on that site and compared the Mercury 2.5 and 3.5hp 4-stroke carbureted model schematics. They both use the same carburetor, the same main nozzle, and the same gaskets going to the intake manifold. Usually that is where they put a restriction, or restrictor plate, with the intent that ‘less air = less horsepower’. I can’t see what they doing for the difference between the two models in regards to horsepower … but it is very common on small OBs that the “smaller one of the same block size”, etc. is de-tuned.</blockquote>