Re: 1957 Johnson 10hp and 18hp gears Home › Forum › Ask A Member › 1957 Johnson 10hp and 18hp gears › Re: 1957 Johnson 10hp and 18hp gears frankrUS Member - 1 Year (includes $3 online payment fee)Replies: 6715Topics: 51 July 2, 2018 at 1:52 pm #78886 I believe the whole units will bolt up, but the gear ratios are different, meaning the gears are different.