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Converting the Johnson/Evinrude 9.9 to 15 hp...?

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Hi DB,

Well your right on more than one count! The Johnson/Evinrude 10/15hp are the same except for carburetor, slight port/timing changes and the majority of the boost to 15hp coming from the tuned exhaust system on the last 10% of the throttle twist. Johnson built--up to a few years ago--a mini hydro ‘racing’ version of the 15hp motor. Aside from the radical lower unit and prop it seemed to be mostly a highly tuned exhaust system that gave this motor it’s 'zing'.

Sorry, don’t have any info. on converting the 10hp to the 15hp though…


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  • Converting the Johnson/Evinrude 9.9 to 15 hp...? - Thom V 20:15:40 03/05/02 (0)


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