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48" Viper

Old 12-14-2006, 07:58 PM
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Esydoesit
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Default 48" Viper

Hiyas All,

Iam new to boating and this forum , I have a 48" viper with a stock G-26 Zenoah water cooled engine
Set up with a Bonzi Clutch, BH. Hanson wrap forward header & Alum. tuned pipe with transom exit, along with a Bonzi water cooled exhuast flange & Bonzi Exhuast tips. Warehouse Hobbies red anodized Dual Rudder system & SPD3 surface drive, Top Secret Trim Tabs, GPS System, Digital Tach, Futaba Magnum 3PM FM 3 Channel radio system with 2400 mah Venom nmh batteries, with a Venom 1200 mah nmh Rx pack & Venom fail safe. I was wondering what the best prop would be for this boat for a little more speed , it runs at 40mph and has only 1 tank threw it , would like to get a little more out of her. The prop thats on it is a 270 Prather stainless.

Thanks )
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Old 12-14-2006, 08:06 PM
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gasfreak
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Default RE: 48" Viper

Try a 275 prop on it or maybe even a 75 mm prop with more pitch, that motor should turn it fine in a hull that length you might be surprised at the difference in speed
Old 12-14-2006, 08:11 PM
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Esydoesit
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Default RE: 48" Viper

Thanks alot Gasfreak , I have no idea about props, would that be a bigger one )
Old 12-14-2006, 08:22 PM
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gasfreak
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Default RE: 48" Viper

yes on a prop of this style the first number is the pitch and the next 2 numbers are the size in millimeters so you are running a 70 mm prop and the 275 will have the same pitch but be 75 mm's in diameter
Old 12-14-2006, 08:26 PM
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Esydoesit
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Default RE: 48" Viper

Cool thanks again , ill try a swap out when the weather gets nicer
Old 12-14-2006, 08:27 PM
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Esydoesit
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Default RE: 48" Viper

it might need a little chop on the water to get it up and running too I suppose
Old 12-14-2006, 08:53 PM
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gasfreak
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Default RE: 48" Viper

Maybe somebody else has another prop suggestion just talking about my experience with these props the 275 is a good all around prop for most gas engines from what I have found
Old 12-14-2006, 09:04 PM
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Esydoesit
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Default RE: 48" Viper

Does it make a difference on surface drive systems ?
Old 12-14-2006, 09:35 PM
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ColumbiaRBoater
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Default RE: 48" Viper

You might even want to try a Prather 280, the Prather props have more pitch as well as diameter as the numbers get larger. Make sure you thin, sharpen and ballance the props also. You say it might need some chop to get up and running, make sure your trim tabs are neutral and try raising your drive a little if it is running too wet. Also who makes the Viper?
Old 12-14-2006, 09:48 PM
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Esydoesit
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Default RE: 48" Viper

Cool sounds good thanks , the hull is build by Vern Kilmer at plumkrazyrc.com
Old 12-14-2006, 09:58 PM
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crazyotto
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Default RE: 48" Viper

looks like a nice boat you got there ...id say 275 also . and or the 67/17/3 blade prop from prop shop or voo doo , ebay has lots of props but buy new !!!
Old 12-14-2006, 10:08 PM
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ColumbiaRBoater
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Default RE: 48" Viper

If your boat is running too wet you should check and see if the bottom is straight. I have one of Vern's 51" Cobramax's and the hook is so bad that on calm water the bow almost plows. However, I have yet to flip it and in chop over 4" it does start to fly.
Old 12-14-2006, 10:14 PM
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Esydoesit
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Default RE: 48" Viper

Thanks all for the info.
Old 12-14-2006, 10:17 PM
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Esydoesit
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Default RE: 48" Viper

Hey ColumbiaRBoater , do you run your boat in the river? I see you live in the same state.
Old 12-14-2006, 10:42 PM
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ColumbiaRBoater
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Default RE: 48" Viper

Yes, I run my boats in the Columbia River from my property. I always check the failsafes and have my row-boat in case one flips or dies to far out.
Old 12-14-2006, 10:50 PM
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Slow Motion
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Default RE: 48" Viper

I'm not familiar with that hull, but most play boats ( non racing ) of that size will be at their handling limit at the mid to high 40's, so you don't have far to go. First off, at one tank, the eng. isn't fully losened up yet, and the high speed needle may be able to be leaned down slightly for more RPM. Move your tuned pipe as far forward on the header as you can, without having the O rings leak. Those alum. wrap to forward and back headers are too long to tune the pipe properly. It could be that your center of gravity is too far forward, particularly with that large hard tank ( fuel ) ahead of the motor. Do you find the boat losens up and runs faster as the fuel gets low? If you set the boat on a flat surface, with a round rod ( broomstick, anything ) under the keel, the RTR boat ( half tank of fuel ) should balance at 26 - 28 % ( for your boat ) of the overall boat length, measured from the transom forward ( around 13" ). You will pick up some speed and not hurt the handling, by removing one rudder blade. A couple of close pics of your transom would be very helpful to see the set up on the running gear. Also, it's very hard to recommend a good prop without knowing the weight of the boat. While the Prathers do an OK job, there are far better blades to try. Try the above ideas and shoot us some transom pics, then we can explore some nice blades.
Old 12-15-2006, 10:34 AM
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Davcruz
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Default RE: 48" Viper

I tried a B/S/T Texas cut SS 280 on my 51" Cobra with a stock Zen and the same tuned pipe, but 90° 3" header and it did not work well at all. Never could get it to hit the pipe with that big prop. I also tried a 6717/3 B/S (I did this prop myself and rounded the ears so that may be why it did not work well) and it had a hard time hooking and was lacking on the top end, Also ran a slightly modded x472 and it did not like that one either. I am running a 73mm Enforcer prop now and she runs maybe 45mph in 3-4" chop and gets on the pipe real nice, hooks well out of the hole too. I have no idea what pitch this prop is, or if it is even still available. I am going to try a 275 on it this next season and see how it does.
Old 12-16-2006, 12:10 PM
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Default RE: 48" Viper

Hi Patrick,
First let me say that the boat comes with both the 270 & 275 prather props. use the 275 on it.
Next, you will find alot of people out here that can help with questions, but be aware everyone has there own opinion.
I personaly built your boat and know it is set up perfect in all ways.
For a boat this size, like someone said, anywhere in the 40 mph range is doing very good.
If you went to a 280 prather prop, you will end up with to much prop torque and the boat will want to pull hard to the right & the RPM's will drop dramticually.
There are alot of props out there a guy an use, but for the most part you will only notice a very small differance, untill you find just that special one that is perfect.
But in the mean time you will have spent $$$$$$$$ to find it.
Each boat has its own personality (per say), you could have two boats built the exact same and one will always be different in speed and handling.
Believe me I have heard just about every thing you can think up about our boats, and to be honest. 98% of it is peer speculation and guess work on peoples part.

Yes, alot of you have our hulls out there, and yes, they are not racing hulls they are sport hulls.
We do not try to compete with the larger boat builders as it is a waste of time, we are a small company and don't have the resourses to keep up with everything in the racing end of it.
The main problem is people love our designs and colors and then want to take them out to the races, and they get beat becuase they don't have them set up properly or any other number of reasons. (wrong motor, prop, setup, ect)
Then all we hear is complaints, why they got out run in there class of racing.

We here at Plum Krazy RC Boats
WISH EVERYONE!
YES!
That even includes YOU!
A VERY MERRY CHRISTMAS & A HAPPY NEW YEAR
Old 12-16-2006, 12:46 PM
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magyarbacsi
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Default RE: 48" Viper

I have one of Verns 48" hulls with a 1st stage mod from Marine Spec. 22cc. with water cooled pipe. I hit 48 mph, gps, and it would not take much to loose it beyond that. Prather 275 prop is the best I found. I also have another of Vern's hull, 57 Cat, with zen 260 and steel pipe, dry, and the 280 prop is too much. That prop used to be on my Homelite, low rpm but high torque motor that could turn it easily.

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