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Direct Drive/Gear box

J

J-bub

Well-known member
Someone (Felber) (Water Thunder) I understand I think using a gear box to reduce rpm to spin prop, but DD is it a different made prop I'm kinda confused with DD how do ya keep from turning such high RPM prop detonation explain the differece please I lookin around for a boat but need explanation in a nut shell [/b]
 
Here is a very simple way to look at it. Direct drive is 1:1 right well get in a four speed car and start in 4th from a dead stop . 4th Gear is 1:1 it will ping and likely stall before the car moves. Just like trucks that haul weight duallies and 1 ton's run more gear in the rear end. The more gear or torque multiplication the more work can be performed! TO a point until gear ratio inefficiencies and the required size of the prop become to big. Me and Mike have talked about the fact a 2:1 gearbox leaves a motor more prone to detonation then a 2.68 gearbox motor! With a DD motor you just put enough prop on it that the motor can only turn the prop just below the point where the tips become super sonic. The more ratio you run the more prop you can swing it's the same way with tires on a truck!
 
You don't turn a dd prop past 3000rpm and it is usually around 72in. In a car motor you don't see all your power at 3000rpm's. The gear box not only lets your motor breath to it's full potential but multiples the torque! Taking the pressure off of the thrust bearing to. It then lets you turn a big 80in prop with a lot of pitch. It is the difference in having a affordable loud boat that will get stuck and one that will push like crazy go where you want to and be quieter. dd Cad would make a good first boat. ride on a gear box boat and you will understand the diff.good luck on your build.
 
Thank you so if I go CAD or CHEVY then definatly a gear box would be the way to go. So if I had stock motor would gear box be easier on crank than DD.
 
Never mind the last reply ya'll answered my questions.. going to build deep side 13/6, 14.0 for first boat and more than likely car motor nuthing fancy but something to get from point a to point be ( experience first then hot roddin) ran a couple boats in high school loners a/c and 305 but low sided didn't care for it nerve racking dont like goin forward and looking back at transom but thank ya'll very much......
 
In my case all knowledge is good knowledge now if I can sell my fishin boat... Merry Christmas guys
 
You know your gearboxes Dan. Should we both tell him all car motor guy's end up with a gearbox in the end and they all wish they had done it sooner! I have yet to hear somebody say man I want to get rid of my gearbox and go back to a DD!
 
J-bub

Are you saying a 13' 6" long boat or a 13' X 6' boat for your first boat?

A 6' wide boat with a gearbox or even DD isn't going to be a lot of fun to run because of the torque roll induced by longer props. Your post just wasn't very clear.

Scotty :wink:
 
13'6 x7 or 7 1/2 I think the higher the sides and the wider the better for me I aint into goin 100 mph sorry W.T. but I want something to push me and momma around so she can hit a frog with a cabbage fan hahaha.. run dry a little aint gotta run B.S Hill all day but if I want to run just water I'll keep my skiff..
 
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