you've got a thru-hub exhaust if there are actually exhaust holes over the engine gearcase round the prop shaft. Non thru-hub is reliable within the prop hub. Non Thru-hub Exhaust Propeller components: This components https://brendadxkp675034.ja-blog.com/29772310/how-much-you-need-to-expect-you-ll-pay-for-a-good-yamaha-outboard-motor-for-sale