outdrive aerators

[gatorwt69]

Hey everyone, I got a question. I have seen on performance boats that on the outdrive they have a spout pointing down to the prop. I guess this is an aerator. I have read a little about them and they say that it helps with plaining time and prop slip. I have just bought a 29' scarab with a 502 that takes a while to plane out and was wondering if that would help. Any info that I can get on these aerators would be great ie: how does it work

 

[Bondo]

Re: outdrive aerators

Ayuh,... You're going to have to come up with a Picture....

The Only thing I can think of that's even Close to your description is a Drive Shower, used for cooling the drive...

Usually,.. The Prop's body is drilled to cause ventilation on take out...

 

[Dhadley]

Re: outdrive aerators

On some performance boats that are hard to get on plane with a full load of fuel they run a hose from the AV plate up above the waterline. When the prop starts to spin it sucks air thru the hose. Once on plane the bottom of the hose is out of the water and has no effect on performance.

Venting a prop doesn't do any good with thru transom exhaust - there's no exhaust in the drive to vent the prop.

I'd bet Wellcraft could give you some ideas on the dimensions etc. If not maybe some of the Offshore race guys on S&F could give you a starting point. That's a pretty popular combo, I'm sure you're not the first guy who needs it.

 

[gatorwt69]

Re: outdrive aerators

I have attached the only photo I can find of what this is. The site, Teague Custom Marine says it will help me plane, and help with prop slip.

 

[Frank Acampora]

Re: outdrive aerators

Yep! That's an aerator or ventilator. In high load applications with high pitched props (sometimes surface running)--like before you get on plane-- you need to keep engine RPM up to where it makes the most horsepower. You don't have thru-hub exhaust to ventilate the prop in that photo SO: you inject air into the prop to cause it to ventilate or slip and RPM goes up. Once on plane, the a/v plate is usually above the water surface so no air is delivered and maxium prop efficiency is delivered.

You can't do this willy-nilly though. You need to research what other hull/engine applications like yours use and start with less air delivery, working up to the best rate for your hull.

 

[steelespike]

Re: outdrive aerators

The pic sure looks like what Dhadley described. I think it vents the prop so its easier to rev to get out of the hole.As Dhadley said it has no effect when on plane.A way to ventilate the prop where there is no exhaust to work with.

 

[TilliamWe]

Re: outdrive aerators

Your 29" boat is just heavy. Aerating a prop is not why your boat won't plane fast.

 

[NSBCraig]

Re: outdrive aerators

Do you have tabs?

Those look interesting, I've never seen them.

I saw something like that on some Arneson Surface drives, though.

I'm just thinking since you didn't mention using your tabs to plane if you had them, cause if not I'd buy them first.

 

[Dhadley]

Re: outdrive aerators

We first started using that system back in the days of racing the Offshore stuff. Yes, tabs were involved but using a surfacing prop and trying to get up with a full fuel load was an issue sometimes. Obviously you used the biggest pitch possible (speed) and it got to the point that if the boat could just get on plane it'd all work out.

Yes, you could use a 2 speed transmission but that took up a lot of room, changed the balance (motors were moved forward) and it was against the rules. We could work around everything but the rule deal.