ventilated props

does anyone know about vetilated props? I heard they're used quite a bit in B.C. but don't know anyone with any experiance. I'm thinking about dropping down in pitch but am afraid of cavitation

What is a "ventilated" prop?

(Message edited by swass on October 24, 2005)

I had one on my I/O, merc high 5. It has holes in the hub, forward of the blades that have plugs in them you can remove to "supposedly" let the prop slip a bit. I guess these are for getting the motor more into the power band??
Damn Swass youve got my checking my grammar

I wasn't trying to be a smart***. I've never heard that term before.

from what I understand the vents let the exhaust out ahead of the blades at startup to provide better holeshot, then at speed there is enough pressure to keep the exhaust going out through the prop. I wouldnt buy a prop just because of this, but you can buy different plugs to fine tune the amount of ventilation.

It works on hole-shot. It does not work at keeping constant speed at low speeds. Try one and see if it works for your application. It only works on through-hub exhaust type IOs and outboards.

its just like the whale tail, everyone has one and they all dont work.

One of the ClubMed boats in Martinique had a worn out lower end where the prop met the gearcase resulting in a ventilated prop. That boat would blow the doors off the other boats with the same hull motor combo's.

Just like Karl said, it's for a quicker holeshot, I wouldn't recommend it for boats running slower speeds. It may cause cavitation resulting in eventual blade failure.

Guess what rodney, they do work and that is why there was one on my last boat and i pulled it off. There also has never been one on my current boat. They help raise the stern so you get on plane faster and can run on plane at lower speeds saving gas.
Swass, I just meant since I saw you post I'd better make sure I at least tried to use proper grammar.

GGGRRRR you made me do it again.
Hey you have any room for Florida brethren? We are planning a trip out your way around the end of January to board and watch some "X"

the holes are positioned radially around the propinfront of the blades? not through the blades, does this sound right

yes they are in front of the blades, the idea is to mix air into the water to allow the blade to reach a higher rpm faster, then once the boat is at running speed the water going past the prop is enough pressure to keep the exhuast from flowing through holes and out the prop hub.

as far as maintaining slower speeds, I dont see where this would be a prob, as long as you get the right pitch!

Bob, are you talking to me? There's always room for one more on the slopes. Where are you going?

Well actually its more then one and we are supposedly heading to Aspen/Snowmass for some boarding also to watch some "X". It would be around the end of Jan. I notice that your 150 miles away though...So do you know anyone with a condo in or around Aspen that isnt $500/night? Id rather stay in a dump and be able to go then not be able to go because of the rediculous prices people want to stay a night somewhere. No offense meant to anyone willing to spend that kind of money for a bed to sleep in.

Depending upon the slower speed, the size of the hole, etc. you can experience "burping" where the exhaust gasses escape cyclically from the vents and the prop speeds up for a few seconds and then "catches" again. Lots of variables, but it has been observed many times. You just don't want it to occur at boarding speeds.