Compression issue

[strombolichef]

My 1996 merc 40 sn 0g369283 was running fine and then all of a sudden one day developed a knock in the top end. I thought of doing a compression check first on the top cylinder is 108 and the other ones are all 1:05. I am thinking I should keep running it as long as I can get it to run and then plan on doing a rebuild on the engine. I believe it to be freshwater all of its life there's no corrosion anywhere on it and generally it seems in good condition has been repainted by a previous owner and seemed to have been well cared for. The boat is older so I definitely don't plan on buying a new engine. Does anybody have any different opinions regarding my plan to keep using it until something fails inside and then rebuild it. Thank you for your advice

 

[Bondo]

Ayuh,.... With those low numbers, 'n a knock in the top-end, it's already over due for as rebuild,.......

 

[racerone]

Perhaps check flywheel nut torque and flexplate if the flywheel has that feature.-----Inspect pistons / rings through bypass covers.----Perhaps check gear oil.