Still confused about compression

[chuckee53]

OK can someone clear the air on compression Ive been reading lots of forums and learning all I can about 2 stroke outboards. If their anything like cars I have to assume 120psi is a respectable number.Some guys are saying they have used motors reading 150psi and another guy says its not uncommen for a new motor to have 90psi.Sounds to me their both a little off so whats the real number??? I have my 84 johnson 150 just bought that misses Ive started with the basics new plugs, new wires still rough. Rebuilding carbs and replacing all fuel lines now and of course timing . I have 80/82 psi in all cylinders and was told as long as they were that close I was good. Yes I tried a new gauge old one read 74per.

 

[joereeves]

For a 1982 model V6, that does sound low on all cylinders. Normally that model is up in the 100 psi range. However, the compression reading depends on the speed that the engine is turning over. If you have a lazy starter, the engine cranking over slow, the reading is going to be low.

Have all spark plugs removed when checking compression, and a known good fully charged battery to obtain the highest cranking rpm you can get.