Thru-Hub
Propellers can be classified 2 ways regarding exhaust gas flow: thru-hub exhaust and non thru-hub exhaust. Thru-hub exhaust propellers are commonly found on “outboard” and “sterndrive” marine systems and are never found on “inboard” applications. This propeller type is part of the boat’s exhaust system as the exhaust actually exits the engine through the propeller (hence the name). This adds some complication as improper exhaust flow can cause a propeller to perform poorly if a prop is incorrectly installed or damaged. A thru-hub exhaust prop is easily identified by the large open exhaust ports located in the prop around the prop shaft. As a result, the diameter of the propeller hub area tends to be considerably larger than it is on non thru-hub exhaust propellers.
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