My Bottom

[Ianfs]

but I don't think they have vented props similar to those fitted to the Bravo Ones and Alpha drives.

They do, the exhaust vents through the props. The "trumpet" style bellows, whilst not glued, slides over the sterndrive tube when the drive is lowered. Whilst there is an escape of gasses around the tube, a reasonable amount still vents through the props,

No, a vented propeller is not a through hub exhaust. It is Mercury's Performance Vented System with vents in the front of the propeller hub which provide ventilation to the leading edges of the propeller at low speeds, which in turn are supposed to stop the engine baulking from propeller grip at low revs, therefore providing a better hole shot.

And yes the tabs on the bellows are there to provide the clamps with a grounding.

Dennis, you must be a closet millionaire!

[mlines]

Ah, ok I didn't know that as none of our props on the alpha drive had that

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[Ianfs]

Ah, ok I didn't know that as none of our props on the alpha drive had that

Understood and I should have been more explicit.

[Dave]

As I understand it, the vents in the vented props, like a Laser 2 and others, allow the exhaust gas to come out of them, spoiling the water flow at the blade root and allowing the prop to spin up through cavitation ..once its spinning to a point where the water effectively closes the vent, you get the grip.....so as a hole shot prop from a standing start they arent that good to be fair, but take off like letting a clutch out on a car or bike.....very useful for race type outboards, particularly big 2 strokes where the power is in the higher rev band, and in some cases probably provide a cushion to the mechanicals when you give them a bootful.. A lot of the vented props have interchangeable plugs of different size centre holes so you can change the rate at which the vent holes are closed by the water as the prop spins up...Some race boats with the high pitch props wouldnt be able to even get on the plane otherwise...

[argonaut]

My High Five prop has interchangeable plugs ... but full blanking plugs are fitted.

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[stingrayfan]

with a rising tide the Discovery would not start. That focuses your mind.

Nightmare. I'm imagining that was like swearing bingo!