Frank keeps trying to lead you in the right direction, but you keep wandering off. It really sounds like you have a piston skirt issue. This motor has a pretty “roomy” crank case and thus a pretty low crank case compression ratio. It can’t afford to give away much and your low compression on the other side of the piston crowns is a warning sign. Piston skirts can be worn without being scored. It took a little digging to find the chart in my Johnson manual but the HD and TD have the tightest recommended clearances the JW being the only one fairly close. .0010-.0025 clearance on the skirts. Also crank mains are supposed to be .001-.002. It wouldn’t take much in both combined to cause a problem. Then add in TCW-3 oil with an effective weight of 20W. Could be your problem.
Here’s something to try. An oldtimer (which I guess I now am) years ago told me he ran all his bushing motors on a 50/50 blend of 40 wt non-det and TCW-3 mixed with his fuel at the factory ratio. The 40 helped seal and cushion the bushings and TC kept fouling and deposits to a minimum. You might have to hit a farm supply to find the 40 wt. There is also a 50 wt aircraft oil that would work well too but the 40 wt is much easier to find and cheaper.
