Re: 1986 Yamaha 40hp Compression Reading
What speed did you have at what rpm last year?
What speed at what rpm this year?
Your compression numbers are probably okay. We don't know how you did it or the conditions, so we cannot judge based on raw psi, except that if they are in a 10% span they are probably quite good. Long shot, loooong shot, is a gasket leak between cylinders.
Don't pull the head yet. We need evidence that your feeling about the speed is correct.
