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made the switch new gear box ratio!

spooledup50

spooledup50

Well-known member
just went to 2.68 box behind my caddy from 1.74 and I'm running a super wide sensinich prop i used to turn the prop 2200 rpms at 19 degrees pitch now im turning the same prop 2200 rpms at 32 degrees pitch and now i have to get one more blade fuel economy and cruise speeds are both way up and the sound is ridiculous i can make phone calls on my boat in motion make the switch its worth the money
 
John,
That Gorilla of a motor with a 2.68 box? Dangit boy! Do you want me to tell Donna to get you another blade to match HE-HE. :wink:

Bob
 
swampjet I am real happy with the 2.37 box. caddys are a little different animal than other car motors. They need some serious mods to sustain high RPMS. just curious about the 2.68
 
It takes getting over the belief that higher ratio mean higher rpms. Regardless of box ratio set pitch to keep max rpms around 4400-4600 and the push will still be there. I built my caddy to turn around 5500 but have it set to 4500 with no complaints. I will be upgrading to a 2.68 in the near future and will still operate in the 4500 range with more and wider blades. I recommend a shaft rocker arm setup regardless of rpms, even if running direct drive.
 
JD I agree with you, and I understand higher ratio more pitch. I must of done the math wrong. what would your engine RPM be if you were spinning a prop @ 2200 RPM with a 2.68 box
 
Utlra wide blades is what I plan on running which are designed for less rpm. Even the blades that achieve maximum thrust at 2200 can be run at less rpms and still be impressive, given there are enough blades. I get better results cruising and don't notice a difference running dry when set to run 2000 rpms (prop speed) on Sensenich K blades except for snap. Just takes a second or two longer to get moving when turning slower. It all boils down to trial and error and I, like so many others on here, don't want to waste $$$ and time on a setup that yields less than satisfactory performance. It comes down to what you expect and even then you are left doubting until you try it on your boat. I don't think there are any simple answers and setups on a boat and it all takes tweaking to get exactly what you want. No matter which way you go...you'll always wonder how the other setup would have been! :)
 
JD, again I agree with you 100%. I believe that spooled stated that he was turning his prop @ 2200 RPM with a 2.68 box. I think that is almost 5900 RPM. I may be wrong. Just trying to save someone some grief and aggravation and $. I am on my fourth 500 caddy motor. they wont take that kind of RPMS for long. I had Buddy Branch build my last motor. I finely found the right place. He knows caddys like thunder knows sbc motors.
 
I missed that part in the post. 5900 on a Caddy is not going to last long unless some big bucks were spent on forged crank, rods, modified intake, and heads. That's at the point where head and intake flow is at or past max airflow (I think the 2115 Edlebrock falls off at 5500) and higher rpm is useless without some major $$$. I think the question needs to be what has been done to the engine. A 2.68 can be run without rpms that high. I'm just guessing here and without knowing all the facts is like shooting in the dark.
 
I just wnet to a 2.68 and a super wide q and all I have is a almost stock 350 and the boat runs hands down ALOT better and fuel milage went up and preformance doubled my boat is now like a new boat all over runs dry great and runs the river at 40 to 50 mph and thats below 4400 rpm . I tried the super q 2 blade and I spun too many rpm going down the river with the pitch set on 2 turning 44 to 4600 to run 30 mph
I added the third blade and set it on 2 and the boat runs a whole lot better turning it now at 3000 to 3300 to run 40 + mph. go figure
 
c chardt":21j3wvpd said:
I just wnet to a 2.68 and a super wide q and all I have is a almost stock 350 and the boat runs hands down ALOT better and fuel milage went down and preformance doubled my boat is now like a new boat all over runs dry great and runs the river at 40 to 50 mph and thats below 4400 rpm .
Click to expand...

No doubt....it's almost like he has a new boat from when I saw it last. Qiuet and strong!!!

Adam
 
You rite John the math dont workout! I am like Jd 4500 at 1890 rpms ! Dont want more push ! It will run 5500 but like 4500 ! Already broke two motor mounts and smash my back bushing into my rigging ! I would say I am at my expections ! :D
 
The max rpms the manufacturers put on the props is not where they generate the most thrust or efficient thrust. The sens. super wides have the same hub shaft as the narrow blades. The maximum rpms is a safety thing and not indicative of the thrust made and certainly not where they recommend you run the blade on a constant level. The super wides were designed to operate in the 1600 to 1900 rpms range. The maximum safe rpm is about 2200 give or take a little. same with the whirlwind MB 2.3.

folks need to change the way of thinking on those big props and the rpms. They were designed to be efficient at much lower than the max rpm rating. They work best with the pitch somewhere in the midrange for a setting. Yes you can put more pitch in and slow them down but you are slapping the air instead of screwing thru it.

I added a fourth superwide just to get the pitch setting back to the midrange. When I finish a monster motor boat later I very well may be running a five blade super wide. I run 3.12 boxes on my big stuff but it is not something most folks can get their brain around because they all seem to think i need to turn a engine 6800 rpms so i can hit the max for the prop. But again I will say the max rom is not the same as the max performance, it is a safety thing only.

Turn em to the right and turn em slow and get lots of blow, ask blackpowder scout he rode behind me last weekend and felt enough about it to comment on it when we stopped.
 
yes its turning way to much rpm i am going to keep my rpms down in the 4500 thats why i need more blades i have those super wides damb near sideways i need more blades to slow the motor down as i have maxed out my pitch but those short 6000 rpm burst shore have some push
 
Spooledup, How long is your prop? Just curious I have a DD 472 and like to keep my day dreaming as specific as possible. I hope to go to a similar setup soon. That gearbox Swampjet has is nice and thin(Blue Thunder I think it's called)Can't wait to see how they hold up.
 
I helped a guy build a BIG Caddy with a big arm in it and he run's a 2.68 Rotator with a four blade super wide and turns his motor 4,600RPM max. I think his boat would blow my boat over if I parked behind him that thing makes crazy thrust at 1,500RPM let alone wide open. If we ever start pulling sleds with weights like the trucks he has the boat to do it!
 
DAVE ON THE MONEY HERE ! ALWAYS IS! HE BROKE MORE STUFF THAN WE COULD AFFORD ! SOMETHING KEEPS HIM GOING !ALWAYS TRYING ! I WAS A LITTLE WORRIED ABOUT MY BOAT !THOUGHT IT WAS A LITTLE OFF THE DEAL ! BUT, ANYWAY I SCALE IT YESTERDAY ABOUT FAINTED! (TOUR BOAT ALL I GOT TO SAY) !BUT BET YOUR BUTT ! I GOT SNAP AND MID RANGE OUT THE BUTT ~!IT WILL RUN THE HILL WITH A LOAD ! GOT TO BEEF UP SOME OF THE RIGGING BEFORE WE STAND ON IT HARD ! ALREADY BROKE TWO MOTOR MOUNTS ! SMASH THE GEAR BOX MOUNTS INTO THE SOCKETS TRYING ANOTHER SET NOW ! I RUN THE TAMPA BAY AREA SO THE SIZE IS ALMOST NECESSARY ,BUT DAM ! ALL I GOT TO SAY IS WELCOME TO FATBOYS TOURS ! :D WHEN THE RACES ARE ON FOR RUN WHAT YOUR BRUNG ! I BE THERE ! HEAVY WEIGHT DIVISION ! ME TOO AND THE BOAT ! :D HAPPY NEW YEAR YALL! GOT TO GO PLAY ! :D PS I WOULD NEVER USED ANYTHING BUT A GEAR DRIVE AND I STILL HAVE ROLL ! :shock:
 
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