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15' panther help choosing reduction and prop

12ftgso480

Active member
Hey guys, really new to the game and just got this boat home. We a 15' x 7'6" sled. It currently has what looks like a stock 350 dd 72" prop setup. Gonna put new poly on and really want to run dry once I'm all put back together. ( don't need to climb hills but do not wanna be stuck in the sand ) I need some guidance with choosing belt reduction and prop. My first opinion is I believe I have room but not sure how far forward I would have to scoot everything with a belt vrs gear drive. Do we think it will affect much on the center weight ratio, does that matter much on planing out ? Does anyone have a similar setup that might be able to guide me in right direction ? My dad has a 6 cyl continental engine that I'm sure we could rip up if it would make more since then buying reduction for the 350? I do not know the exact model of the continental but can get it. I'm starting in the dark here and just want to succeed without swapping different ratio and prop multiple times. Any help/info is much appreciated. We currently only have 90hrs on 350 and would be more familiar working on it than the continental but the continental could be more cost effective if I only have to bolt a prop on it without a reduction box.
 

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Hayes96

Member
Hey guys, really new to the game and just got this boat home. We a 15' x 7'6" sled. It currently has what looks like a stock 350 dd 72" prop setup. Gonna put new poly on and really want to run dry once I'm all put back together. ( don't need to climb hills but do not wanna be stuck in the sand ) I need some guidance with choosing belt reduction and prop. My first opinion is I believe I have room but not sure how far forward I would have to scoot everything with a belt vrs gear drive. Do we think it will affect much on the center weight ratio, does that matter much on planing out ? Does anyone have a similar setup that might be able to guide me in right direction ? My dad has a 6 cyl continental engine that I'm sure we could rip up if it would make more since then buying reduction for the 350? I do not know the exact model of the continental but can get it. I'm starting in the dark here and just want to succeed without swapping different ratio and prop multiple times. Any help/info is much appreciated. We currently only have 90hrs on 350 and would be more familiar working on it than the continental but the continental could be more cost effective if I only have to bolt a prop on it without a reduction box.
I was wondering who bought this boat in north Texas. Where ya from? I was close to buying it the day it was posted but the carbon rigging and no title detoured me. Probably the cleanest older panther on the planet! Now to answer your question, with poly and a new 72” ww whisper tip narrow the 350 it has will push it good enough to hunt with and will slide it across wet grass for a little ways as long as you stay wide open. But it will definitely not take off dry. It would be more for shallow water/mud use. Now, to add a reduction you’d need to modify the 350 with a different cam and valve springs at the very least to accommodate the added rpm since you’re going from 3000rpm DD to ~4600-5000 with a reduction. Preferably a new set of 180cc or so aluminum heads as well. I also do not think you have room in the cage to slide the engine forward enough inside it to make room for the reduction unit and also don’t forget the prop will sit higher as well (no longer at crankshaft centerline).
 

12ftgso480

Active member
I was wondering who bought this boat in north Texas. Where ya from? I was close to buying it the day it was posted but the carbon rigging and no title detoured me. Probably the cleanest older panther on the planet! Now to answer your question, with poly and a new 72” ww whisper tip narrow the 350 it has will push it good enough to hunt with and will slide it across wet grass for a little ways as long as you stay wide open. But it will definitely not take off dry. It would be more for shallow water/mud use. Now, to add a reduction you’d need to modify the 350 with a different cam and valve springs at the very least to accommodate the added rpm since you’re going from 3000rpm DD to ~4600-5000 with a reduction. Preferably a new set of 180cc or so aluminum heads as well. I also do not think you have room in the cage to slide the engine forward enough inside it to make room for the reduction unit and also don’t forget the prop will sit higher as well (no longer at crankshaft centerline).
Hey there bud ! I'm in Oklahoma right on the ks line. Yea I'd say she's pretty clean and low how. My first thought on pics before I made the drive was some probly robbed some goodies off it and put this old prop on it. I got to digging around and came across this gear reduction on here 2:1. I just sent guy money yesterday so hoping to have it the end of this week. I have not called whirlwind to see what they would reccomend as far as a prop goes. I'm hoping we can reduction mounted with a new prop without much trouble. My dad and i were just discussing the plan last night. Was thinking we would try this box with new prop and see what it will do before we pull all rigging to put poly on. I'm sure it's gonna take some modifying to make it all work. I was nervous about the title aswell but I have a lady who can title 42 just takes awhile. Hopefully there no major issues there! Thanks for the response, may end up looking for an ls motor if this 350 requires too much work or money. Thanks for response. I need all the recommendation I can get.
 

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kwanjangnihm

Moderator
Gearbox is more or less half the weight of belt drive as well
FYI on gearbox weights!

Stinger: 66.2lbs (weighed by Waterthunder)
Ox box: 68lbs
Rotator: 70lbs
Precision (airboat gear drives): 66lbs (manufacturer reported)
Torque Drive Gearbox: 70lbs

CH3 Belt Box:132lbs (Weight breakdown)
Upper Unit----60lbs
Lower Unit with bearing----23 lbs
Main Housing-------42lbs
All bolts and belt----7lbs
Total---------132lbs
 

One Eyed Gator

Well-known member
Like Kwan mentioned gotta slide motor stand slide forward which means rebuilding the rear of the engine stand and lowering it as well, longer radiator hoses

You mentioned an LS - Stock 5.3 without all the Car/Truck Accessories is maybe 325hp, stock 350 is around 225-260hp. LS platform 6.0 iron motor with aluminum heads is about 50 lbs lighter as well.
With a Cam swap you can get 25-75hp
gen 3 5.3 can be had for 300-1200.00 depending on what you want.
gen 4 4.3 may be a little more but comes with the TBSS style intake after 05 I believe
6.0 is a little more expensive but a noticeable bit stronger.

After running an LS motor I don't think I would change back to a caddy or SBC

www.car-parts.com is a US wide search engine all you need to know is the year and make of the vehicle for the motor you want.

All depends of your budget.
 

12ftgso480

Active member
Like Kwan mentioned gotta slide motor stand slide forward which means rebuilding the rear of the engine stand and lowering it as well, longer radiator hoses

You mentioned an LS - Stock 5.3 without all the Car/Truck Accessories is maybe 325hp, stock 350 is around 225-260hp. LS platform 6.0 iron motor with aluminum heads is about 50 lbs lighter as well.
With a Cam swap you can get 25-75hp
gen 3 5.3 can be had for 300-1200.00 depending on what you want.
gen 4 4.3 may be a little more but comes with the TBSS style intake after 05 I believe
6.0 is a little more expensive but a noticeable bit stronger.

After running an LS motor I don't think I would change back to a caddy or SBC

www.car-parts.com is a US wide search engine all you need to know is the year and make of the vehicle for the motor you want.

All depends of your budget.
Thank you very much for all the useful information after learning more about this 470 motor I believe we will be going LS with my gear Box earning more about them everyday think I've just been running from the future of electronics shout out to everybody on all the responses. You guys are alright!! Is everybody running the holy terminator set up on their LS hear they're worth the extra money? Also where are you guys getting headers for those motors?
 

One Eyed Gator

Well-known member
Norman Clay Innovative Accessories
Headers and Straight thru race style muffler ( sound great but not quiet)

I've run a Holley HP setup in the gulf area for 3 years without any issues.
 

90chevy396

Well-known member
Terminator x is not designed to get wet so must be mounted in dry box I went with the terminator x because a buddy has a lot of experience tuning with this system. Using the wizard and no manual tuning set to 12:1 WOT and 13.6:1 cruise and 14.7:1 idle the self learn has killed 2 O2 sensors in about 50 gallons. Still have to get with tuner to iron out the particulars. I am using Bosch 17232 sensor as it is $80 with 1 year warranty from oriellysand same sensor that comes with the kit but with a 6” shorter cable
 

12ftgso480

Active member
Little update guys, decided to go Ls!! Picked up a 2:1 balistic. Have yet to decide on a prop, will probly all be a winter project for we are unfortunately right in middle of a remodel. Anyone got decent blades to swing behind this thing they'd ship? Been watching the classifieds, think we'll be going with sensenich prop if we don't find a decent used. Got trunion upgrade with motor, Think we'll leave everything els as is for now and if it won't run where we want we can add cam and more tune later ?
 

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Coastslider

Well-known member
I think most guys are running 2.55-2.68 reductions on the LS motors. They can turn a larger wider blade than the 350’s. Keep us all posted on your build and good luck
 

White Hawk

Well-known member
There is a ton of info in the archives of this site. a 2.68 will allow you to swing a wider and larger prop. The gearbox is a torque multiplier. The JX or JR series are good examples of a prop style that can be effectivly paired with a 2.68. You will add pitch to your prop to get your W.O.T. or wide open throttle into the 5200 to 5600 rpm range a 2.68 gear box will put your prop speed around 2000 give or take depending on the actual RPM you choose. Talk to your prop manufacturer about your HP and pair it accordingly!
 

Aeon

Well-known member
that LS will not like the 2/1 reduction. when i blew up my 454 with a 2/1 i just swapped a stroked LS3 in and left the 2/1 belt. it spun a 78" 3 blade falcon prop and not very hard. With out taking all the pitch out the taller gear just would not spin the prop. This was a built 427ci ls3 not a stock motor.

flash forward to now same motor with a 2.55 ox box and a 3 blade 82"JX set past the 2 mark and she spins like crazy and works like its supposed to.
 
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