Surface drives.

[Britboater]

A total opposite to our boats, these props would give you a few cuts! Very impressive how efficient they are with being more than half out of the water, no doubt right up @Speedling street .

 

[ar240owner]

That's a cool vid !!!!

 

[OrangeTJ]

That boat is MOVING!

 

[buckbuck]

Yikes. Looks like turbines spinning.

 

[scot71]

I was always under the impression that this is how the props on the unlimited hydroplane boats worked. It's very cool that you can get that kind of speed with basically half a prop.

 

[scot71]

Hey @Speedling, here's your speed solution. lol!

 

[Speedling]

Yup! Looked at these several times and it is very interesting. The danger aspect makes it very unsuitable for my kids.
Not going to modify my yamaha for sure!
If i get a go fast boat i would be torn between jet and anderson drives like those. Thing is i would love something like a 28' catamaran that had a closed bow and jet. The characteristics of the hull makes a surface drive work much better though.

Bottom line is i need a 100mph roostertail, am i right?

 

[Speedling]

It also makes me think and research a bit.
Why don't we have counter rotating impellers?
What happens if we don't use the vanes/stators to straighten the flow?
The most inefficient part of a jet is the friction of the water flowing through the pumps, so who cares if it swirls out the back?

 

[Seadeals]

Throwing a dart; but if you didn't streamline the flow after the impeller (counterforce to the impeller rotation), would it possibly allow an efficiency-disturbing vortex to develop impacting the inflow to the impeller?

 

[txav8r]

It also makes me think and research a bit.
Why don't we have counter rotating impellers?
What happens if we don't use the vanes/stators to straighten the flow?
The most inefficient part of a jet is the friction of the water flowing through the pumps, so who cares if it swirls out the back?

Because the engine turns only one direction. The simplest drive is what we have, no transmission or redirect gearing to lose HP. So your stuck with one of two solutions to get counter rotating impellers...either build the mirror image motor and have two different motors, so that one spins clockwise and the other counterclockwise, or gear it to reverse the direction the impeller turns mechanically.

 

[Speedling]

Throwing a dart; but if you didn't streamline the flow after the impeller (counterforce to the impeller rotation), would it possibly allow an efficiency-disturbing vortex to develop impacting the inflow to the impeller?

Like a toilet!
I think this question needs testing to prove true or false and probably has speed and volume limits as well. It could possibly assist the velocity to the inyake as well but could create aeration at the impellers. But if you think about it, if that were the case then the impellers would create the vortex before itself anyways in our current setup and create cavitation. We don't so i would assume that we wouldn't in that situation either.

 

[Speedling]

Because the engine turns only one direction. The simplest drive is what we have, no transmission or redirect gearing to lose HP. So your stuck with one of two solutions to get counter rotating impellers...either build the mirror image motor and have two different motors, so that one spins clockwise and the other counterclockwise, or gear it to reverse the direction the impeller turns mechanically.

So realistically a gear setup would be the only way to go to test the theory and then you would lose the same or more friction losses as you would gain with no vanes.
However, a side benefit to this would be that pump loading would be the same on both sides eliminating the need for different pitched impellers.
One more thing of note is that the mr1 is already gear reduced so changing that gearing so one spins the opposite wouldn't be that difficult from a manufacturing point of view. Does impros offer reverse impellers?

 

[txav8r]

So realistically a gear setup would be the only way to go to test the theory and then you would lose the same or more friction losses as you would gain with no vanes.
However, a side benefit to this would be that pump loading would be the same on both sides eliminating the need for different pitched impellers.
One more thing of note is that the mr1 is already gear reduced so changing that gearing so one spins the opposite wouldn't be that difficult from a manufacturing point of view. Does impros offer reverse impellers?

gear reduction and reversal are two very big differences, and the later will cost HP and torque where the first one doesn't cost much and actually increases torque. I don't think there are many non direct drive jet boats, so my bet is that reverse pitch impellers would be costly as a one off production.