Ok I understand the prop dimensions and what they do. But what are the pro's/con's, differences, whatever in a through hub exhaust vs. over hub exaust.

This would be on an older 225 evinrude.

Adam

Great question!

There are allot of answers here. The exhaust tube carries the exhaust gases past the working sides of the propeller. The over the hub props experience more blow out on hole shot than through hubs do. This is why the PVS system was invented for the through hub props. To help in the ventilation of the blades and the hole shot.

The exhaust tube also becomes an extension of the gear case. Therefore, it can become a planing surface with elevated engine heights and surface piercing propellers. It can also increase the drag of the lower unit.

Most ultra performance applications like allisons, etc. benefit from the over the hub props due to the lack of drag. They don't require the extra lift.

Most standard boating OB applications will benefit from through hub designs.

Thanks for the lesson bblades.