you do have a thru-hub exhaust if there are actually exhaust holes about the engine gearcase across the prop shaft. Non thru-hub is stable around the prop hub. Non Thru-hub Exhaust
From seasonal outboard motor https://isaiahejtc317574.blogsvila.com/29850104/the-2-minute-rule-for-yamaha-4-stroke-outboard-motors-for-sale