there is a thru-hub exhaust if there are actually exhaust holes to the engine gearcase around the prop shaft. Non thru-hub is sound throughout the prop hub. Non Thru-hub Exhaust carrying out the outboard maintenance https://tasneemneyp232424.ambien-blog.com/35929956/getting-my-refurbished-outboard-enginesfishing-boat-outboard-motor-to-work