The 9.5 and the 15 are the same motor the carb is the only difference. Check the serial number ona a small coin like spot on the engine block and go to the johnson web site to find out how old it is. Check it for color to be sure it wasnt overheated and try starting it. Put it in water for 15 minutes before you try starting it if it hasnt been run in a while. I bought a 15 horse Johnson that was bought new then set for over 20 years without being used. The electric pack was shorted out replasced that and it has worked like a trouper ever since. I put a lot of stress on it and it holds up great. I researched a web site where the guy knows those motors inside and out I cant think of his last name his first name was Leroy google johnson motor repair he might pop up Hope this helsp 500 isnt bad if it is what you want.