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 Anyone have a PowerThruster for their OB?		  New Topic  Topic Locked
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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts
Initially Posted - 08/21/2007 :  18:10:37  Show Profile  Visit delliottg's Homepage
I saw [url="http://shop.trailersailor.com/detail.htm?fno=300&group=294&cat=2601"]this [/url]on TrailerSailor today, wondering if it's worth the money? I wouldn't mind having 30% more fuel economy, but it sounds too good to be true. Anyone have one of these installed? If so, what are your thoughts?
David
C-250 Mainsheet Editor


Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --
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britinusa
Web Editor

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USA
5404 Posts
Response Posted - 08/21/2007 :  22:02:31  Show Profile  Visit britinusa's Homepage
David, we looked at that too. I have seen others that totally encircle the prop.

Note that the item they show is fitted to a very short shaft motor, where the prop is much closer to the surface, I'm guessing that would be where the most benefit is found.

We were looking at the full encloser model (can't find the link) because it claimed to reduce 'walking' significantly while also improving directional thrust.

I'll keep looking.

BTW, not cheap for a couple of SS plates!

Paul
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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts
Response Posted - 08/21/2007 :  23:00:19  Show Profile
A number of new powerboat designs are using "tunnel drives" that put the prop in a half-cylinder in the hull, apparently for the same reason. The risk, and possibly the reason outboard manufacturers don't make them, is that if it bumps something (like a piling I hit once with an outboard), it could be bent so the prop hits it. Similarly, propeller guards, to prevent line wraps and injuries, have been considered and rejected. That "thruster" probably doesn't go full-circle for the same reason.

The other approach is what Honda and Yamaha do--lower pitch and larger diameter props. The less the prop is like a paddle-wheel (as a higher-pitched prop tends to be), the better its directional thrust at very low boat speeds (like standing still).
Edited by - Dave Bristle on 08/21/2007 23:06:15
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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts
Response Posted - 08/22/2007 :  07:40:11  Show Profile
During the seaweed blooms, that device would make clearing your prop somewhat interesting.
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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts
Response Posted - 08/22/2007 :  08:56:25  Show Profile
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by dlucier</i>
<br />...that device would make clearing your prop somewhat interesting.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
I always found a burst in reverse did it... Another consideration, though, is that apparently you drill four holes in your anticavitation plate, so if you decide to get your money back under the unconditional guarantee, the holes are forever.
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ClamBeach
Master Marine Consultant

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3072 Posts
Response Posted - 08/22/2007 :  09:05:44  Show Profile
The concept has been around since 1934, usually called a 'Kort Nozzle' or 'Ducted Prop'.
They are usually a full circle around the prop and the ring has an airfoil shape to manage flow. If engineered properly they are good for generating extra low-speed thrust (up to 45% from the same power) and stern lift.

They are primarily used on large vessels pulling heavy loads. (trawlers, tugs etc)
How effective this little one would be... dunno. Might do some good.

More info here if you're interested.

http://www.marinepropulsion.net/kort/nozzle.htm
http://www.navweaps.com/index_tech/tech-023.htm
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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts
Response Posted - 08/22/2007 :  09:16:25  Show Profile
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Dave Bristle</i>
<br /><blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by dlucier</i>
<br />...that device would make clearing your prop somewhat interesting.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
I always found a burst in reverse did it...<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

If only it were that simple!
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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts
Response Posted - 08/22/2007 :  09:21:52  Show Profile
If this "PowerThruster" had any merit, one would think that at least one the major outboard players (Honda, Mercury, Yamaha, Tohatsu, Bombardier) would have stumbled upon it.
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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts
Response Posted - 08/22/2007 :  10:14:45  Show Profile
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by dlucier</i>
<br />If this "PowerThruster" had any merit, one would think that at least one the major outboard players (Honda, Mercury, Yamaha, Tohatsu, Bombardier) would have stumbled upon it.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
I suspect the whole concept breaks down on a planing boat, for which most ouboards are designed. At speed, the lower unit is carefully designed to minimize drag and withstand substantial forces as the boat bounces, slips sideways, etc... That piece of sheet metal might not meet those requirements in that situation, but it might do some good on a boat that never exceeds six knots, and where enhanced thrust for starting and stopping would be useful. I suspect that the higher the pitch on your prop (regardless of diameter), the more it will help.
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Sloop Smitten
Master Marine Consultant

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USA
1181 Posts
Response Posted - 08/22/2007 :  12:26:50  Show Profile
One area it might help is with side wash from the propeller. I know I have to turn my port mounted outboard slightly to port to prevent the wash coming off my propeller from placing excessive sideways force to the rudder. If it would provide some additional low end power, raise the MPG, and minimize the side wash it would seem a useful addition, but I'm betting you could make your own for under $20.
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Ed Montague
Captain

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USA
499 Posts
Response Posted - 08/23/2007 :  23:13:29  Show Profile
OK, I am a sucker for gizmos and gaggets. I first saw the Power Thruster at the Catalina Rendevouz on Catalina Island a few years ago. The gentleman who has the patent was present and selling them for $60. I didn't buy but was interested. The following year I attended the Rendevouz and looked forward to taking advantage of the discount. No luck, he wasn't there.

I ordered it and installed, (Yamaha High Thrust 9.9) yes, four small holes to drill. This thing is stoutly built. I think I could have built one but not as well. We have used it on some long trips including our recent trip to the Channel Islands last month. I am certain that I got more miles per gallon then in the past. I kept expecting to run out of fuel and the motor just kept on going. Another advantage was I could maintain 5 knots at lower RPM and lower noise level. I don't have any financial interest in this thing. I believe that by directing the force of the prop more directly back this gizmo actually works as advertized.

My 2 cents.
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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
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