Really good compression for TD’s and TN’s is about 75 psi, but they will idle OK down to about 70 psi. Your rings are probably just stuck. They run on 16/1 gas oil mix so the rings rarely wear out. Instead the primer seals wear out long before the rings wear out and that is what puts them out of use. Lots of good info at pochefamily.org/outboard. But note that the ad there for my new primer seals and installation instructions is about 15 years old. I had to raise the price to $10.00 about 5 years ago as it’s getting harder to find the proper leather to make more.
