Re: 1972 80hp merc
If you are getting 155 on all cyls you are doing very good. Not sure what the factory spec is but 155 is great. More importantly than the actual compression number is the uniformity of the numbers. If one cyl is way off (more than 10%) then that reflects a problem.
Other things to consider is the condition of the wiring, how well does it run, what controls do you have already etc etc.
