On my last boat I had to convert my mercury to 25" shaft after Don mounted bracket for me/took me about 2 hours (I changed water pump too and new lube. Member "deepsushi" hooked me up with a guy who sells them dirt cheap..I pm'd you with details and email contact address to vendor. So email him and see if he has any in stock that will fit your application... or buy one at
http://www.baymfg.com/mercury.asp
-Fred