78 55 Hp johnson 3000 rpm only

[Carson007]

Hey guys so I’m a new owner of a 77 Tempest SS160 with a 78 55 hp Johnson motor which is not going past what I believe is 3000 rpms I’ve changed spark plugs so far an that hasn’t made a blind but of difference I’m hearing power packs but hoping not the case have not checked spark have not checked compression will be doing so when I have the time but any other ideas would help greatly

thanks

 

[oldboat1]

If running temp is safe (roughly 140F, never 160F), test run using a timing gun to see if spark is dropping out on either lead. No flash, no spark -- 2-person operation for safety.