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Reduction - Prop Question

Ron Miller

Ron Miller

Well-known member
Hi all and I know I am in the right place for this question . We just had a slight bearing problem with our Stinger reduction and Sharon has done an excellent job of helping us.. Here is the question...
We have a 15' x 8' AGI Alumitech hull 30" sides --- 540 stroker with 550+ hp. and a 82" Power Shift Maximus prop 3 blade...
Now we had a 2.38/1 stinger reduction but we are changing to the 2.68/1 ratio.
My pitch was right near center on the hub mark and using a framing square off the transom measuring to the trailing edge it was set at 1/8" for grate performance....
How Much More Pitch Should I add to start out ??????? :?:
 
most of the time this equation will work out. evey 2 degrees of pitch will nock off approx. 150 rpm's on top per blade.and every 1/32 of an inch on the shank at the refference mark is one degree of pitch.so i would just guess start of 1/16 inch past the center parting of the hub. i am not sure but when i ran a powershift patty said you could go up to 1/4 inch past the parting plane and be safe i guess it is still the same.
 
A 540 with a 2.68 should swing a 3 blade Maxim pretty dang good! I would start at an 1/8 past center! I never put too much effort in the first pitch because you know your gonna change it! I would go an 1/8 past it and see what you think!
 
I heard 5/16 and i don't know how your supposed to call it? I call it off of the front half edge of the prop hub. I have run them at a 1/4. Ron i hope shipping goes smooth and you get it going in time! I am all ears on how your going to like the upgrade. I would like to know if noticeable. Sound push snap and how much more pitch you can swing with the 268.4. Good luck keep us posted. Hey Bondsman cool feed back 8)
 
Thank you for the info . I got her tore down tonight all except for the prop hub bolts to the reduction Those hex heads are soaking in penetrating oil tonight .. Hope to have it going for this week end and I will let you know how it runs.. Thanks again.

PS-- Rick the state shoot went well top team ? 525 fish. Next MACA run is Sept. 22 just south of Geiger Rd. Saginaw bay.
 
Lady luck is with me -- after setting with penetrating oil on the hub bolts to the reduction unit for 24 hrs they all come out and are on the new reduction unit on the boat --- whew--- Now tonight I was doing some math and with the 2.38 at 5ooo. rpm = 2100 prop rpm the sweet point for the Maximus but with the 2.68 I will have to turn 5800 rpm to turn the prop at 2165 rpm. OR is their a different rule for the biger reductions units --- ( just set to run the way you want it to.?? ) Tomorrow night I just have to torque things down and balance the prop before putting it back on the airboat.
 
5500 rpm will get you 2052. I would set the pitch by what max rpm you want. That Maximus will still perform awesome.
 
You will be able to swing more pitch a a slower tip speed. advantage. sound and snap. You have a longer prop so IMO the Max. will do good a 1900 to 2000. If you could fit it go to a 84in. The extra gear will also take some pressure off of the motor. If you are willing to turn a little over 5000 with more pitch in it i think you will see a difference?! I have a feeling you will have those blades at max pitch.I see a four in the future 8)
 
After setting the pich 3 times I still say that everything has to be designed from front to back to make it work correctly. Just because we have 600 hp and a 3 blade power shift maximun wide blade it dose not mean that going to a 2.68/1 reduction will work.. Our 540 engine was built so it would produce maximum horse power at 4800 RPM so turning it any faster just shortens its life.
The setting of pich.
2.38/1 we had grate out of the hole 5 on board from a dead stop we were on plane in ? 30 feet. and at 3000 rpm we were doing 28 to 30 mph and at 4000 rpm we would run 36 to 40mph depending on the water and wind conditions. Max RPM 4800
Now with the 2.68/1
1 - 1/4" past center on the hub for maximum pitch our boat was sluggish out of the hole and at 3000 rpm it would do only 26mph and at 4000 rpm we run 36 mph.
Max RPM 4600
2 - pich set 1/8" past center it was good out of the hole but at 3000 rpm we would do 28mph and at 4000 rpm it would only do 32 mph Max RPM 5000
3 - 3/16" was right in the middle of the other two and bad fuel consumption

Now don't get me wrong if our engine developed HP up to 6000 rpm then I think we could make this 2.68 work very well but only turning 5000. max we just can not get enough RPM out of the prop to make it do its job correctly.

Correct me if I am wrong or if I missed something --- BUT If you are thinking of changing something make sure you check all of the numbers before you start tearing things apart.
 
Crowhater is running a 530ci motor and went to a 268:1. Instead of adding more pitch, he backed the pitch off a little and went to a 4th wide blade. I think he is happy with it.
 
Seems like it would work for you but it looks like you tried every setting :? Tip speed is key in your setup and with a 4800 to 5000 limit your not getting it? Your torque must like to pull against a 238. With the length of your prop i would have thought you would have loved it. The only other way to make it work is to go to the 4 bl.or go back in gear or turn the motor harder. Goes to show you every set up is different. Thanks for the feed back.
 
Ron Miller":24wzo8ky said:
After setting the pich 3 times I still say that everything has to be designed from front to back to make it work correctly. Just because we have 600 hp and a 3 blade power shift maximun wide blade it dose not mean that going to a 2.68/1 reduction will work.. Our 540 engine was built so it would produce maximum horse power at 4800 RPM so turning it any faster just shortens its life.
The setting of pich.
2.38/1 we had grate out of the hole 5 on board from a dead stop we were on plane in ? 30 feet. and at 3000 rpm we were doing 28 to 30 mph and at 4000 rpm we would run 36 to 40mph depending on the water and wind conditions. Max RPM 4800
Now with the 2.68/1
1 - 1/4" past center on the hub for maximum pitch our boat was sluggish out of the hole and at 3000 rpm it would do only 26mph and at 4000 rpm we run 36 mph.
Max RPM 4600
2 - pich set 1/8" past center it was good out of the hole but at 3000 rpm we would do 28mph and at 4000 rpm it would only do 32 mph Max RPM 5000
3 - 3/16" was right in the middle of the other two and bad fuel consumption

Now don't get me wrong if our engine developed HP up to 6000 rpm then I think we could make this 2.68 work very well but only turning 5000. max we just can not get enough RPM out of the prop to make it do its job correctly.

Correct me if I am wrong or if I missed something --- BUT If you are thinking of changing something make sure you check all of the numbers before you start tearing things apart.
Click to expand...


Ron,
I have never run the 2.38 so I can not say how it would work on my rig. I like the 2.68 much better with the 4B then I did with the 3B for sure. My motor is good to 5000-5100rpm and that is it period. My peak torque is 3800rpm at 650lb and at 5000 I am at 590lbs. I have had several people tell me to try the 2.38 with the 3B and I thought about the 2.5 that stinger makes also.

If I could I would try all of these combos but it cost money do do this stuff. This year I have changes my reduction gears, bought a 4B super wide, had the motor freshened up, reworked the boat, and I am reworking my trailer. My duck hunting budget is starting to look like the goverment war budget. I will run what I have this season and by the end on january I will know everything there is about this set up.
 
crowhatter boy do I feel the same way .. I wish we had an endless bank account so I to could try different set ups and I do think a wide 4 blade would do us well in performance and sound --- But not now at $150.00 for a fill up to go play...
Thanks to everyone for your help and ideas especially Sharon at Stinger .
PS. I would love to reduce the pich so I could spin it up to 5800 so the prop would do 2100 but we have one cylinder with a bad gouge in its side from the last whoops and our mechanic says NO DON'T DO THAT.. Because it can not be bored any more. and we don't want sleeves.
 
WELL RON ! SAME THING ON MINE SORT OF . WHEN I INSTALLED MY SUPER WIDES AT 2 PITCH RPMS WERE AT 4200 OR SO !SHE FLEW , BUT CHANGED TO 268 SHE DID ABOUT THE SAME AS YOURS AT 5000 RPMS ! ABOUT SAME PROP SPEED AS BEFORE ! STILL SOMETHING WAS LACKING . ANYWAY PITCH IT AT 3 MOTOR RPMS AT 4300 ! AND BANG HERE CAME OLD BOAT AGAIN ! POEPLE SAY I AM STRAINING IT AT THAT RPM BUT SEEMS TO LIKE MORE THAT WAY! CANT REALLY EXPLAIN IT ,BUT IT SNAPS AT THAT PITCH BETTER THAN THE OTHER WAY .SORT OF WEIRD! MY TORQUE PEAK IS AT 4200 SORT OF EXPLAINS IT !TRY A LITTLE MORE PITCH MITE BE SURPRISED! GOOD LUCK
 
So it sounds as if all that preaching Thunder has been doing for the last year about a 2.68 always being better and out performing a 2 to 1 and a 2.38 to 1 was just BULLSHIT!
 
The higher ratio's are making our boats quieter. Turning big fat props slow with a lot of pitch is key.If your motor doesn't like rpm's then sound is the big advantage. If it does then you can have the best of both worlds.If all out push is the goal then tip speed is key. The higher gear takes some pressure off of the motor too. If you match the prop and box at the drawing board stage it is a lot better than mid stream. It looks like 4 sw and a low gear push hard and is real quiet.
 
Tony...Thunder's setup only works on a lightweight setup (Aluminum LS motor with light hull and riggings). The 2.68 ratio does not work on larger or heavier boats. 2.37 or 2.38 to 1 ratio seems to be the best all around ratio for most setups. Also, it depends on the engine and it's power range.
 
better- lick- her !!( great name ) My rig ( barge ) is no where near 100% rite yet, but i can tell you its HEAVY....
and i have a 2.68 stinger behind a cadillac powerplant, on a 16 ft hull. and it comes out of the hole quite nicely, so dont be so sure it only works on ls's. i have alot more tweeking to do before its all over but im at this point only rev'n out to 4700 rpm's so if you've got the wood behind the box there is no need to chase higher than normal rpms. all its doing is allowing your engine to do more work with less actual strain.
 
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