I have a mercury 9.9, serial 0C298526 long shaft. I ran the motor all of last summer. Runs great. Maybe a little temperamental when starting after being warmed up, of course that could be due to the operator. From cold, starts on the first pull. If setting for an hour to 3 hours, I never know whether to full choke or half choke, or not to choke. Pushes my 24ft pontoon boat at max 7.2 mph (Humminbird 58i1i gps) with me, my wife and daughter. Ran great last time out, this past Sunday. Once I got home, I did all my usual checks, and was checking the plugs (looked perfect, i.e., not fouled,yet not bone dry....passed the hole shot test) and checked compression. Now I know motor should be warm, throttle WOT, etc, but I got 60 psi on both cylinders. (Motor ran so well when I bought the damn thing, I never put a compression tester on it) Clymer and everything I've ever read says minimum 100 psi ( I know from my chrysler experience that the 35 hp 1962-1980 or 81 the range is 95-105). And I have read the most important thing is variance between cylinders, not the actual value. I've only messed with reed valves one time prior...a 9.9 mercury, same vintage that wouldn't idle nicely, even after carb rebuild. On that motor, I noticed the reed block was rusted to hell, corrosion everywhere, and the reeds weren't closing completely(daylight and then some when holding the reed block up to a light). Sorry for all the rambling, but my ultimate question is how much would an open or defective reed affect compression readings? I believe my compression tester to be somewhat reliable, i.e., my 1972 chrysler 35hp consistently gives me 95 on each cylinder (range is supposed to be 95-105). Used it on all of my previous outboards, and gave readings within expectations. I use the same testing procedure for all motors. Can an outboard with 60 psi on both cylinders run that well? If so, I won't complain.
