oil is mixed with the gas.-----Some oil / gas mixture goes right through the motor.----I say it is normal.----Was there any water INSIDE the gearcase that drained out with the gear oil ?
If adjustment at shift lever is correct , take lower unit apart.----Inspect bronze bushing above pinion.---Inspect bottom bearing surface on driveshaft.---Insoect forward gear and clutch dog.
??----Plastic parts are cheaper to produce.-----It is all about being able to market a product for the showroom.----Not designed with future repairs in mind !!