Konrad you are an your way to getting on the lake its just going to take some time. A real good website to get merc questions answered is iboats.com there is a mercury/mariner forum that can really help you out. The compression numbers you have may not be that bad as compression gauges vary. As long as the numbers are within 10% of each other which yours are close you should be able to get out on the water. What transition zero was talking about when doing a compression test was to have the butterflys in the carbs at the wide open throttle position when doing the compression test. Also when doing the test have all the spark plugs removed to allow the motor to turn over quickly and freely and a hot battery is a necessity. One last item on your first tank of gas get some Sea-Foam from your local Auto parts store (about $5.00 for 1 pint can)and run that with your first tank of premix. That stuff does a great job of cleaning up the carbs and helping clean the combustion chambers and the carbs clean.
Costa
Costa