The timer base has a groove in it like the crankcase sealing rings. You lube the groove in timer base, install plastic ring on timer, snap into recess in head,install clamps and make sure its free to rotate
The idle air screw has nothing to do with oil mix. Oil/fuel ratio is controlled by oil pump or if disabled how much oil you add to fuel tank. This is oil pump and rod(pic) and rod should be connected to carb.
There was a pressure fitting that mounts in threaded hole to supply air pressure to boat side oil tank. Plug it off as it can cause cylinder to run lean and a fire under cowling.
You should hear the VRO/OMS click about every 30-45 seconds at idle..clicking noise is 100% normal as this is air motor poppet releasing the return spring. If its clicking rapidly there is a air leak
Use the CCMS( Chris Carson) reeds or TDR (Tony Doukas)...Boyeson wont last but a couple of years if that. The CCMS reeds are plug and play with no need to rejet