Re: 1978 Johnson 2 hp Home › Forum › Ask A Member › 1978 Johnson 2 hp › Re: 1978 Johnson 2 hp lloydUS Member - 1 Year (includes $3 online payment fee)Replies: 453Topics: 4 September 23, 2018 at 9:19 pm #83430 I have both an Evinrude and Johnson version of that motor that ran and idled well. They need about 120 psi to run well as I recall.