A Photo & Discussion Forum for Wharram Design Enthusiasts
Sorry for not thanking you for your abundant info. I did buy a Prop- Guard -- I suppose it does help a little, but not as much as I had hoped. Now that I am in SW Florida where the Manatees roam -- I feel better to have the prop protected. I will keep looking for a proper Kort -- the physics on the 'Prop-Guard' is not at all engineered. The 'nozzle' effect without a 'shape' (airfoil cross section) can not deliver any real benefits. The only effect I can see is the water being contained off the prop ends -- maybe?
If you still have the Handler -- I will buy it.
Mirko Sebastian said:
Hi Thomdid you find a nozzle?Found this in a German forum...Cheers MirkoKort Nozzles are almost universal in heavy pulling boats like tugs and towboats. Because they apply power so much better. Some even have these on rotatable extensions so thrust can be applied in any direction, kind of like with a outboard, except such units can be huge. Think 10'-20' propellers, maybe more. A google on kort nozzles will turn up more than you want to read about them in general.
I got the used Handler nozzle off ebay for $112.50. The person auctioning it did not know what it was. It has the number H915-111-3 stamped in the nozzle. It's in near new condition. A couple small paint chips missing inside. I'm only interested in getting as much of my money back out of it as I can.
It came with nozzle, a matched prop, and some hardware. There appears to be enough hardware to mount it twice and even two drills. It mounts with 4 bolts on the cavitation plate and one through the bottom of the skeg. The special prop mounts the normal way, it's a regular looking prop with the blade tips machined off so it rotates in the nozzle with a very small clearance. The prop has marks on the blade tips that probably line up with the ring mark inside the nozzle. This prop is about 9" dia, no markings except a felt tip 15, not sure on pitch.
The nozzle I have will fit a outboard with about 10.25" between cavitation plate and tip of the skeg. On my 9.9 that's about 2" shorter than the distance, though it matches the cavitation plate shape and the skeg pocket is right if it were just larger. Since the prop has the right spline for the 9.9 and mounts fine, I've assumed it's for a smaller Yamaha high thrust. Sure wish it would fit mine, not only more thrust, but some prop protection.
There's not a lot of info online as the company appears to have given up. They probably priced it too high. It was a new product in about 1999. A google on "handler outboard nozzle" will turn up about all there is. Here's a few quotes:
"A Yamaha 9/9 hp high thrust outboard equipped with a standard 9.25" X 11.75" prop generates 70 lbs. of forward thrust at 2000 rpm - 110 lbs with the Handler installed. Reverse thrust with the standard prop is 45 lbs.; with the Handler, 70 lbs."
"Port Kent Marine, Inc." Handler P.O. Box 311 Port Kent NY 12975-0311 U.S.A. (514) 637-2566 (514) 637-8449 Outboards 4-45 (most Outboard Makes) Serge Harrison $419-725
"This is a Kort nozzle propeller and is not marketed as a direct prop-guard. The product has some customer testimonials as well. Manufacturer statement: ""Bi-directional power-control-economy""; increased fuel economy (20%), markedly greater thrust (up to 100%), eliminates cavitation, increased engine life by reducing RPM levels 30-40% for same thrust."
I've not contacted that number, but the website that was also listed is dead. Note the prop size listed above is reversed as the standard prop on the T9.9 is a 11.75" dia x 9.25 pitch. A T8 is probably turning a 9" dia x 7 pitch.
Note there are a few other outboard nozzles, including one the defense department paid for that's very nice, fully enclosed for working around troups in the water. It's a full lower unit replacement. But I'm not sure any are specific to the high thrust Yamaha. Nozzles have a rep like propeller guards of slowing the boat, but these engineered ones may have the opposite effect.
I don't have a nozzle myself, above was a post from 2004 by firstname.lastname@example.org
Meanwhile I talked with a 'Prop Guard' rep and the boat technician of German life guards DLRG:
- even the latest 'Propguard' devices slow down planning life boats considerably (50km/h instead of 65km/h)
- floatsome can bend or break it and then the entire lower unit (prop, shaft, etc) gets warped
- nevertheless to protect swimmers a Prop Guard increasingly becomes a regulatory requirement for life guard boats
- The shape of an efficient nozzle ist not a big secret, basically a Naca series 00 profile rotated into a donut shape does the job. Crucial is a good fit to the prop. See http://www.propellerpages.com/?c=nozzles&f=How_Nozzles_Work . A good welder or a fiberglass builder should be able to make one from a drawing.
Would be nice to have feedback on 'Prop Guard' performance for slow moving, high trust boats such as Wharram cats.