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Jeremy, to give you an idea about the competitive difference between the 2cyl 45 versus the 3cyl 49...
Ya the 49 is technically more cubes. But the 45 has larger bore, and longer stroke. Plus, engine aside, they both have 2 carbs, but the 45 has the larger ones. And it sounds like they run the same RPM.

Thanks, Ya i was curious was all..figured if they turned rpm,or were like the xs they would be fast, and it sounds like they dont, and knew the speed was not tested yet on a v bottom.

The biggest difference is the Mercury is a poorly designed motor compared to the OMC. Not only the combustion chamber design but the intake design. The 2 carbs feed 1.5 cylinders each thru reeds mounted on the crank. That is why the later 52 and 60 cubic inch motors have 3 carbs and the reeds are in the normal position behind the carbs and feed one cylinder each. The 650XS has a larger intake, 3 large carbs and 3 large reed cages.