Mercury 9.9hp 4stk 2008 low compression

[Jimbo341b]

I have a Mercury 9.9hp 4stk 2008 outboard with poor performance issues having a maximum of 5000rpms when it should be around 6000rpms. A dry compression test gives me 125psi on both cylinders whereas a wet compression test gives me around 160psi. I was originally considering doing a rebuild and replacing the piston rings to improve performance. However, I recently purchased a cheap small USB camera and took some photos inside the cylinder. The quality is not great but can anyone help me interpret these? There is a lot of carbon build up inside the cylinder, but also what looks like corrosion. Will a ring replacement help or would I need to re-hone or even re-bore the engine block?

https://imgur.com/a/NtLDNMu

 

[racerone]

I can not see an issue.----What boat ?---New to you motor ?-----Did it ever run at 6000 RPM for you ?----Maybe just need a different prop ?

 

[Jimbo341b]

Boat is small 9ft soft inflateble around 50kg. Motor is 2nd hand so I don’t know how many hours of use. Performance was better before and it’s steadily getting worse. Uses much more oil now than it did before.

 

[faztbullet]

Perform a leak down test...