I have a 69 merc 650 that has run great for years. Suddenly after a long high speed run (about 5000 RPM) after stopping at idle for a minute when we went to take off, no power, instead of 35 MPH we get 7 mph and about 3000 rpm max or less. Starts easy, idles good, does not miss or sputter. At home checked compression, 120 lbs times 4. Plugs are black, (not used to this normally pretty clean) But pulling one wire at a time seems to be runiing on all 4. Any Ideas of what might have gone wrong? A couple of things. We used some kind of new BP gas with some kind of new aditive called invigorate, not sure what it is. Also, earlier that day, we forgot to open vent on tank and it ran great till it nearly colapsed the platic tank and stalled. But it ran fine for an hour after that. Sounds like it runs OK on Muffs but Iknow that means about zip.
I am open to and appreciate any suggestions on where to start.
I am open to and appreciate any suggestions on where to start.