This exact engine has not been made since 1992, a shortblock isn't available for it either. On this machine, you may be able to use the 11hp Briggs listed here, but it is likely that you may have to cut the hood or frame below the air cleaner for this to match up. If the new engine you buy does not have a 9 amp or larger alternator on it, you will have to change it over from your original engine.
