Re: 1973 merc 200
I also think 80psi is low, but suspect it's the gauge or test method since it's cranking easy warm. The float level has to be set to spec perfectly, the choke plate has to close completely, along with a clean carb and proper low speed tuning. Those motors are notorious for being hard to start cold unless they are in perfect tune. The primer bulb should be firm before attempting to start it as well. I believe over time the cable on the cable operated chokes get stretched or whatever, and not close the choke totally. Try getting a friend to actually pull on the choke knob while you start it, or just pull out the knob and look at the plate in the carb throat. If there's a difference in the choke plate position when you pull the choke knob and hold the knob out, and when you pull the knob and release it, that could be part of your problem. I think there's even a plastic gauge included in the float kit for setting the float at the exact proper height. My father's best '72 merc 20hp liked a pull through with the choke on, then push in the choke and it would crank on the next pull. BTW, I don't think the throttle position or the temp. will affect your compression test much.
Hope this helps,
JBJ
