"No, the cylinders are always
"No, the cylinders are always getting oil, even when not firing - since it's a 2 stroke, it's imperative that oil get to them for lube even if they are "not really in use".
This particular system is often referred to as Merc's 2+2 - not sure if it was a Merc or a Yamaha invention.
Anyhow, the oil pump still mixes oil with the gas and sends it to all the carbs. The carbs for the two cylinders not in use have modified low speed jets (which make it important to keep the carbs straight if you ever pull them).
The jets for those cylinders only let enough of a gas/oil charge through to keep the cylinders lubed. So they do waste a bit of gas, but it is quite minimal (and considerably less than if you were idling all 4 cylinders).
On the electrical side of things you have High/Low speed stator windings (all in one unit)and two switchboxes - both parts of the stator feed one switchbox (which fires the 2 cylinders that run all the time at both high/low rpms) and the second switchbox is only fed by the high speed windings (which always produce power but only get up high enough to fire a sparkplug around the 1500-1800 rpm range).
At that rpm the crankcase vaccum is now "sucking" enough that the carb has moved on to it's high speed jets and gas flow is "normal" at all carbs.
It's that point before everything kicks in that can be a little rough - the engine is almost gasping one second, then running full tilt the next.
As far as the Merc guide, it has probably moved. Cliff (Marine Engine) has been doing quite a revamp and trying to put together more information pages - all should be back soon "bigger and better" than before..."
