Yamaha 9.9 4T oil consumption

[TownsendsFJR1300]

Well, you know the old rings were worn.

New rings helped, honing would have helped more..

You have/had some ring "blow by" which would have been found with
the leak down test.

Compression was getting past the compression rings, pressurizing the crankcase, then blowing out into the intake manifold where it is eventually
burned..

IMO, sounds like your about done at this point.

[rodbolt17]

and t is the difference between a patchem up and a rebuild.

patch it and it works kinda.
bore it and return the piston to wall clearance and ring gaps back to factory and it works.

[pakostane]

I had some time and I made compression test:

First cylinder (cold, 2 days not work)



Second cylinder (cold)





First cylinder (hot, 10 minutes work at idle)


Second cylinder (hot)




In service manual I found compression 139 psi on new engine. I think it is good compression.