benefit to controlled propeller ventilation?

[jonr]

If I understand correctly, creating some ventilation will allow a propeller to create less load and allow the engine to rev into its maximum output range. As the boat comes up to speed, the ventilation could be eliminated to prevent over reving. I'm interested in increasing acceleration without effecting top speed. Would diverting some exhaust through the prop shaft and releasing it in front of the propeller during acceleration work?

[Frosty]

Mercury issued a modification 30 years ago on how to drill holes in the font of the blade root into the exhaust hub to allow a heavy loaded Mercriusrer engines prop slip to get out of the hole.

[jonr]

That would be the basic idea except to put a modern control system on it to make it variable. Ideally the engine would operate at full rpm during the entire acceleration.

[Frosty]

Are you aware that a surface prop and submerged prop is as different as --a horse and a cow? Looks similar.

[marshmat]

Propellers modified in this way are available from stock for Merc engines. They vent a bit of exhaust gas between the blades; apparently it improves acceleration on some engines that would otherwise have trouble revving up at lower boat speeds. Examples:
http://mercuryracing.com/propellers/bravoioutboard.php
http://mercuryracing.com/propellers/maximus.php
It was a major marketing point a few years ago but now appears to be accepted as routine practice for certain applications.