Once you start into an engine, reality sets the play. If it just needs hone and rings, fine. But if the valves are so so and the cylinders are worn, then the job is what the job is. Squirting some oil in is a good way to get an idea of what to expect before you open it up, but the reality is in the seeing.
One other thought. Just bought a '92 F150 for my high school age son. 300 ci inline 6. 137,000 miles. Compression was 115, 125, 135 , 125, 125, 120. I ran one tankful of gas through it with an engine oil and fuel treatment decarbonizer - called Bluechem. Oil change after one tankful of gas came out like syrup with carbon. Compression changed to 139, 145, 150, 150, 150, 142. ONE TANK OF GAS! Mind you, the engine was dirty even though it had always been run on high detergent DELO oil. The concept behind the Bluechem is that it pulls the carbon deposits down small enough to completely emulsify in the oil. Fuel treatment cleans top side valves and pistons/rings and oil treatment cleans out the rest of the motor and ring grooves, loosening up the rings so they aren't sticky and allow them to move again for better compression. Works best with Moly type rings since they wear less than iron rings, in my opinion.
One thing to note, we tried it on my 3.0 liter with similar compression numbers as your 2.5L and it did pretty much nothing at all to change compression numbers. I figure this is since most boats never get hot, and they get the oil changed so often that they never really get dirty. Cleaning out the carbon does nothing about actual engine mechanical wear. Because our older Merc engines have iron rings in them, and they are run at high power settings pretty much 100% of the time, they wear a lot more than the average pickup motor. When I ran the cleaner through the boat the oil came out looking like the day I put it in. Clean and clear. Only reason to try the decarbonizer is if you have carbon buildup - IMHO.
