I use hard wood,1/4 inch square, 2 inches long, one end tapered to 1/8inch wide, and tapered from the center of the piece of wood, to the end of the wood with a final thickness of 1/8 inch, so it will fit on top of piston, then slide it onto exhaust lip, then turn engine over to raise the liner up. The way I check the seal, compression, is the remove the engine from. in this case, the boat. I hold it in one hand and spin the fly wheel as fast as I can ,from, BDC, thru top dead center with the plug in tight. As I turn the engine over very fast thru TDC., If there isn't a good tite fit, thru TDC, I grab the appropriate liner squeezer, and bring the liner fit, back to the piston, until I feel a good tite fit, for a good seal,@ TDC. If the liner to case fit is so tight, U have trouble removing the liner, from the case, before U remove the liner, I would. pull the motor out, put a tite glow plug in, grab the fly wheel, and spin the engine over TDC, and U can feel if there is good tite seal, or very little seal, @ TDC .If U take the head of, and take a close look at the piston, all around the edge, id U see some groves around the edge, I believe, the liner is so tite into the case, it just wears the piston top edge away, and with out a good seal, U loose a lot of horse power. When people send me an engine to look at, most the time it is either bad bearings, or no seal. @ TDC. I pull the liner and sand the OD of the liner, until the liner slides in the case very easy. Then I take the liner, and sand the OD down until, the liner slides into the case, with out any resistance. Then I squeeze the liner, and bring the seal back in, to nice tite fit, so the owner can brake the engine in again. Hope this helps. JM2CW
dick jonesy