I don't know what motor you are running but if it is a Yamaha Saltwater series, the 'precision oiler system" adjust the oil to gas ratio based solely on the throttle opening position.
At wide open ratio could be 40:1 but at idle it could be 100:1. Regardless your oil burn seems way too high. In most of these cases, the problem is that the oil pump linkage is not adjusted correctly or the linkage has broken or come loose in which case the spring moves the linkage to the highest oil feed rate. At that oil rate at trolling speeds I would expect smore exhaust smoke than normal. In addition, if that oil rate keeps up, after some time, your plugs may start to foul.
So if you have a Yami SX motor, take a look at the oil pump linkage.
It is also possible but not nearly as common for the oil to leak out. Look in the bottom of the lower cowling for oil and look at the main (on the motor) oil tank for oil on the outside or fittings/hoses.