Cavitation plate
- Thread starter MikeV-Drive
- Start date
Carnivalride
New member
What gears and what kind of power do you have? An 11-3/4 is a BIG wheel, if you don't have the power or gear to burn that it sure might try and "man handle" your boat. lolcoolglastron said:
I used to have an 11-1/2 x 15 with 29s and it didn't have enough power to flash or man handle the boat. :smile19: This was back in 92 when I was first starting with it. 18s made a big difference but still not enough power to man handle it but it pulled skiers and got mileage. :smile28:
been busy working on my little problem and finally had a chance to view this thread . a cool thread
for sure and carnivalride has posted up some food for thought. a lot of factor's are involved in making it
take a set and they( ALL GOT TO WORK TOGETHER ). when i got my flat it did not have enough leverage for pushing the plate far enough down , + the motor was set too far back just killing the center of gravity .
( motor placement is also another criticl factor ) for the H P of the motor + the gearing + the prop .
also on the prop issue . no two prop's even of the same size and pitch and make will react the same
each one will want to as i say do there own thing just got to work and twik them .
look at your H P first then consider gear and prop size . :smile17:
for sure and carnivalride has posted up some food for thought. a lot of factor's are involved in making it
take a set and they( ALL GOT TO WORK TOGETHER ). when i got my flat it did not have enough leverage for pushing the plate far enough down , + the motor was set too far back just killing the center of gravity .
( motor placement is also another criticl factor ) for the H P of the motor + the gearing + the prop .
also on the prop issue . no two prop's even of the same size and pitch and make will react the same
each one will want to as i say do there own thing just got to work and twik them .
look at your H P first then consider gear and prop size . :smile17:
Carnivalride said:
I'm running a 496 with around 700ish HP. The gears are 22s and I'm spinning the prop right around 6700. My power should be around 7000. I don't know that for sure since it hasn't been on a dyno other than pulling a stainless AT "A" 5750 RPM. On the impellar chart thats right around 675-700 HP. The cam is Comp Cam XR292R. The advertised power band is up to 7200.
The prop isn't bogging the engine any, it just tends to want to make the boat "dance". :smile16: Thanks for the input!
73 Sanger Flat
Active member
Have you GPS this yet ??.
Here are some number , but without the prop slip , can not calculate the speed exactly. So let us know if this is close ..My prop slip about 16-18 %
6700 rpm / 22 gears ./15 pitch and 15% slip = 98.66
6700 rpm / 22 gears ./ 15 pitch and 18 % slip =95.18
6700 rmo/ 22 gears ./ 15 pitch and 20 % slip = 92.86
a 11 3/4 inch diameter prop is big for a flatbottom . You might want to try a smaller prop or go down a gear size to 18 and that would pick your RPM up to wear you want them .. I think dropping to 18 will net you around 3-400 rpm ..
I would try a smaller prop if you can borrow one ,
Lorenn I am sure will know more that me on this ,
Here are some number , but without the prop slip , can not calculate the speed exactly. So let us know if this is close ..My prop slip about 16-18 %
6700 rpm / 22 gears ./15 pitch and 15% slip = 98.66
6700 rpm / 22 gears ./ 15 pitch and 18 % slip =95.18
6700 rmo/ 22 gears ./ 15 pitch and 20 % slip = 92.86
a 11 3/4 inch diameter prop is big for a flatbottom . You might want to try a smaller prop or go down a gear size to 18 and that would pick your RPM up to wear you want them .. I think dropping to 18 will net you around 3-400 rpm ..
I would try a smaller prop if you can borrow one ,
Lorenn I am sure will know more that me on this ,
duanehydro
Active member
GPS.....that's funny, he's still learning which way is forward.....no need for the fancy electro-devices yet. :grin:
Carnivalride
New member
coolglastron said:
Is the boat "dancing" because of the way it goes across the water or is the prop lifting it? I agree with Billy I'd probably try and borrow a smaller diameter prop like a 11 to 11-1/2 and see what that does first. Now the smaller diameter prop will most likely bring the rpm up so you may not want to change gears just yet. Since you have a 496 with an XR292R cam I really don't think you need a lower gear unless you have an awesome set of heads. What I mean is the 4-1/4 stroke tends to have more torque so it's better at pulling a taller gear. Once again this is something you'll have to experiment first and see what your boat/combination likes.
Billy's speed/slip numbers are right on so let us know what your "flash" rpm is and if you can borrow a GPS what the top speed is. Then we can do so calculating from there.
Carnivalride
New member
This isn't directed at Billy since he's still learning how to use his "playback tach" is it?!?!? LOL :shocked: :shocked: :grin: :wink:Duanehydro said:
73 Sanger Flat
Active member
I know how to use a GPS , but that memory tach messes with me when i want to make a pass. I think I get to involved at looking and driving the boat and forget to hit my mometary switch to start the recording .. I need to borrow a msd checker to learn how to operate the tach . That how Jim showed me was with a MSD checker ..
Let us know if you can borrow a GPS and see what your slippage is ,,
Let us know if you can borrow a GPS and see what your slippage is ,,
Carnivalride
New member
I figured you'd deny this. LOL :laugh:Brazos River Rat said:
I think the dancing is coming from the prop. It goes away after the boat has some speed. And, it's really not that bad but, there isn't a real noticeable flash either. But, more seat time will tell the tale. I have one of these tachs.-----> http://atracingworld.com/NEW-TYPE-R-5-11000-RPM-4-IN-1-TACHOMETER--RECALL_pE7BB7FF7-6D7F-44B6-B1CB-6A4BCA0782AA.html