Re: 1968 18hp vs 1972 25hp johnson Home › Forum › Ask A Member › 1968 18hp vs 1972 25hp johnson › Re: 1968 18hp vs 1972 25hp johnson lindy46US Member - 1 Year (includes $3 online payment fee)Replies: 496Topics: 41 July 23, 2018 at 10:17 pm #79983 The water tube part numbers are the same for both engines: 313777 The drive shafts have different original number but both are replaced by part number 325800. So I assume they will interchange.