Centrifugal pump for boat propulsion
Centrifugal pump for boat propulsion
(OP)
Designing an electric powered personal fishing catamaran.
We started with two trolling motors for propulsion and differential thrust steering but the trolling motors must draft at least 15". The craft drafts only 5" and we would prefer to have propulsion wherever the boat will go.
We have recently embedded the trolling motors vertically in the hulls and attached flat-backed impellers to the shafts. We then covered the impellers flush with the hulls, exposing 90 degrees of the 360 degree rotation to the water below and also cut a 2" hole in the cover to let water into the center.
The boat actually moves forward and reverse, but very slowly. We need someone with sump pump savvy to help us improve efficiency. We know that our straight vanes are not as efficient as spiral shaped vanes, but that would prohibit reverse.
Any guidance would be appreciated,
John Zimmerlee
Marietta GA
770-565-4420
We started with two trolling motors for propulsion and differential thrust steering but the trolling motors must draft at least 15". The craft drafts only 5" and we would prefer to have propulsion wherever the boat will go.
We have recently embedded the trolling motors vertically in the hulls and attached flat-backed impellers to the shafts. We then covered the impellers flush with the hulls, exposing 90 degrees of the 360 degree rotation to the water below and also cut a 2" hole in the cover to let water into the center.
The boat actually moves forward and reverse, but very slowly. We need someone with sump pump savvy to help us improve efficiency. We know that our straight vanes are not as efficient as spiral shaped vanes, but that would prohibit reverse.
Any guidance would be appreciated,
John Zimmerlee
Marietta GA
770-565-4420





RE: Centrifugal pump for boat propulsion
I have seen small outboards equipped with centrifugal pumps instead of gearboxes and propellers. They're not a marvel of efficiency, but your rig is probably much worse; the volute is an important part of a centrifugal pump.
Mike Halloran
Pembroke Pines, FL, USA
RE: Centrifugal pump for boat propulsion
I'm not smart enough to argue any points, but I've seen something similar at www.vortapowersystems.com and believe that the theory, though not as efficient as propellers, should work for this craft. I just need some help with the volute design and some estimate of how much less efficient straight vanes are compared to spiraled.
StreamDancer
RE: Centrifugal pump for boat propulsion
Mike Halloran
Pembroke Pines, FL, USA
RE: Centrifugal pump for boat propulsion
You also might put a suction through the hull and discharge to the the rear using a disc for a the pump.
http://www.discflo.com/literature.htm
RE: Centrifugal pump for boat propulsion
It would likely need a very efficient suction screen, which may also block fairly readily.
RE: Centrifugal pump for boat propulsion
There is a trade off between output and current consumpion, however you may find a compromise in the medium sized pumps. with say a 2" discharge.
B.E.
RE: Centrifugal pump for boat propulsion
Since reverse is not possible and speed control is non-existant, I would have to use 12 pumps - one of each of 3 speeds in forward and reverse on both sides. the expense at $40 each along with the mounting nightmares and additional weight became overwhelming. Even so, the proplusion was not enough.
StreamDancer
RE: Centrifugal pump for boat propulsion
yours
RE: Centrifugal pump for boat propulsion
This project was commended in the 2005 Intl Concept Boat Competition for its introduction of foot control to a personal fishing craft. Each foot has control for forward/reverse and speeds for each trolling motor . . . creating differential steering. Adding the mechanical reverse thrust would complicate the foot switch control.
The craft needs to be controlled in reverse speed and direction as aptly as in forward.
StreamDancer
RE: Centrifugal pump for boat propulsion
yours
RE: Centrifugal pump for boat propulsion
How about going in a different direction. Leave the motors vertically mounted and place a Voith Schneider propellor on the end of each. You would not need the steering function for your use. you could use your differential steering via motor speed. The site I have linked here is for a model not a full sized one.
ht
B.E.
RE: Centrifugal pump for boat propulsion
Formed a tri-hull with kayak-like hull down the center, tunnels on each side, and sponsons just outside the tunnels. Utilized trolling motors with 10" props in raised tunnels at mid-point in craft. The props cavitated profusely, so I lowered the tunnels. Stil cavitated until I got them so low that the tunnels were no longer needed. The original objection was to get the propulsion up high enough that the boat would be under power wherever the boat could float.
The Voith Schneider props looked interesting, but I can't find any one producing them. Every site talks about design and prototype.
I just can't believe that moore attention hasn't been spent on a shallow water propulsion system. The only one that seems to work is Vorta Power Systems. That appears to be nothing more than a sump pump with lateral discharge.
If it works for them, it should work for us!
StreamDancer
RE: Centrifugal pump for boat propulsion
Manufacturer at www.voithturbo.de
A.
RE: Centrifugal pump for boat propulsion
Try spinning a tin-can lid with a hand powered drill and lowering it into a tray of water. You'll be amazed at the thrust, and the mess, it produces.
Mike Halloran
Pembroke Pines, FL, USA
RE: Centrifugal pump for boat propulsion
The Tesla disc pump may be the answer. I emailed them for help this morning. I'm not sure what you mean by a stripper blade and wonder about the fender. If this disc churns up the water and/or splashes alot, the fish will swim for their life and the purpose will be defeated.
I am hoping for a cost effective quiet efficient system.
If that were possible, someone else would have come up with it years ago!
Stream Dancer
RE: Centrifugal pump for boat propulsion
RE: Centrifugal pump for boat propulsion
Using a trolling motor (on each hull) turned vertically with 5" dia impeller (8 blades, each 1.5" wide), I was able to get the boat to move forward and reverse. Performance speed was only about half of what regular trolling motor props would do.
The good news is the boat only drafts about 5" and the propulsion system works wherever the boat will go.
I first had the impellers and the discharge area covered with a plate. A 2" round hole was cut just above the center of the impeller. Exit ramps (forward & aft) were exposed just beyond the discharge area. Performance was marginal.
I soon cut the cover off of the discharge area so that the entire forward/reverse ramp was exposed along with about 3/4" of the blades. That made an improvement, but the inlet hole was still getting clogged with weeds and such.
Then I open the area between the hole and the ramp on the cover. To my surprise, improvement again.
I'm now spreading the width of my exit ramps to get a little more cross-sectional area to push against.
I really need a pump guy to look at the design. An experienced pump person could probably tell me where I can improve without doing any calculations.
Stream Dancer
RE: Centrifugal pump for boat propulsion