4 blade vs 5 blade for heavy load

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Swamp Thang
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4 blade vs 5 blade for heavy load

Post by Swamp Thang » Mon May 22, 2017 9:56 pm

The 3 blade 79 inch R isn't going to be enough prop for my heavy 14x8 DB so I'm trying to decide if the 5 blade is worth the extra $$ or is it a waste?
I'm getting ready to order the mild cam 632 which should be about 650 hp at 5200 and 800 ft lbs at 4,000 it will have a 2.3 belt drive.
The whole rig is probably going to weigh somewhere around 2300 lbs before passengers and gear so this pig will need some serious thrust on dry stuff, top speed isn't important but the main concern is will the 632 have enough balls to turn 5 super wide blades with sufficient pitch to maintain a decent cruise speed and fuel economy or would it do better or about the same with 4 blades, I'm thinking it should do about 1 mph for every 100 rpm with this hp to weight... so top out at maybe 50 or so and cruise at 30 at hopefully no more than 3500 rpm's
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CarMotorBarge
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Re: 4 blade vs 5 blade for heavy load

Post by CarMotorBarge » Wed May 24, 2017 4:13 am

Do you want to turn R blades (wide) or S blades (super wide)? Also how many RPMs do you plan to turn at WOT? The S blades can only turn 2100 RPMs.
14x7.5 Al David hull with 14 inch transom
419 CI Horsepower Barn LS3 with 2.88 Ox Box swinging 4 blade 83.5" R
GTO Rigging and B&S Tilt Trailer

Swamp Thang
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Re: 4 blade vs 5 blade for heavy load

Post by Swamp Thang » Wed May 24, 2017 11:35 pm

I'm thinking the S blades for the low rpm push, with the 2.3 I can only turn the engine about 4800 and lose probably 40 hp if it builds all it's hp at 5200 but still have all the torque. I might need to go with a 2.5 so I'm not leaving meat on the bone. I'd really like to keep the max rpm's around 5200.

CarMotorBarge
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Re: 4 blade vs 5 blade for heavy load

Post by CarMotorBarge » Fri May 26, 2017 7:21 am

The 2.5 ratio will definitely help with the S blades. Get the 2.5 ratio and turn the motor 5100 to 5200. Also I would go with a 4 blade S instead of a 5 blade S. You aren't making enough HSP to turn a 5 blade. The S blades take a ton of HSP to turn.
14x7.5 Al David hull with 14 inch transom
419 CI Horsepower Barn LS3 with 2.88 Ox Box swinging 4 blade 83.5" R
GTO Rigging and B&S Tilt Trailer

Joe
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Re: 4 blade vs 5 blade for heavy load

Post by Joe » Fri May 26, 2017 7:39 am

I run the same boat with an all iron bbc. I have a 2.68,wish I'd have kept the 2.3 but. I have a 3 blade S and the boat does everything you could want. Mine is set up single front triple rear.
Even with 650hp I don't think you could turn a 5 blade S with enough pitch to warrant the expence. 3 or 4 blade should be all you need. Good luck
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Re: 4 blade vs 5 blade for heavy load

Post by SHOOTER250 » Fri May 26, 2017 6:31 pm

I have the same boat with A 700 horse big block and a 2.3 belt I went with the 84 inch three blade JX it turned out to be the perfect prop for my set up you should look into it also it's an awesome prop.
it snaps up very quick pushes like a dozer and is reasonably priced money well spent.
It can handle all the horsepower your 632 can give it

Swamp Thang
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Re: 4 blade vs 5 blade for heavy load

Post by Swamp Thang » Sat May 27, 2017 12:04 am

CarMotorBarge wrote:The 2.5 ratio will definitely help with the S blades. Get the 2.5 ratio and turn the motor 5100 to 5200. Also I would go with a 4 blade S instead of a 5 blade S. You aren't making enough HSP to turn a 5 blade. The S blades take a ton of HSP to turn.
You're probably right, the 2.5 would get the most out of this engine with the cam & head specs. I'd have to turn a lot more rpm's and have more gear to build enough power to turn 5 blades with that much area. I'd really like to keep it low lift/ rpm/ and maintenance.

Swamp Thang
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Re: 4 blade vs 5 blade for heavy load

Post by Swamp Thang » Sat May 27, 2017 12:11 am

Joe wrote:I run the same boat with an all iron bbc. I have a 2.68,wish I'd have kept the 2.3 but. I have a 3 blade S and the boat does everything you could want. Mine is set up single front triple rear.
Even with 650hp I don't think you could turn a 5 blade S with enough pitch to warrant the expence. 3 or 4 blade should be all you need. Good luck
What cubic inch and hp/tq are you running Joe and could you tell me what you like or dislike about the different ratios, the 5 blade probably is too much for my engine, the last thing I want to do is lug it.

Swamp Thang
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Re: 4 blade vs 5 blade for heavy load

Post by Swamp Thang » Sat May 27, 2017 12:21 am

SHOOTER250 wrote:I have the same boat with A 700 horse big block and a 2.3 belt I went with the 84 inch three blade JX it turned out to be the perfect prop for my set up you should look into it also it's an awesome prop.
it snaps up very quick pushes like a dozer and is reasonably priced money well spent.
It can handle all the horsepower your 632 can give it
I haven't given that one much thought but I will, I recently put a new 2 blade 72" JW on my Gpu and I was very impressed... very smooth power delivery. the swept blade design has a lot of snap and is quiet.

Joe
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Re: 4 blade vs 5 blade for heavy load

Post by Joe » Sat May 27, 2017 4:36 pm

I've never put it on the dyno so I can't give definitive answers on torque and hp but it's right around 550hp. It has felber mild ported heads and his 496 cam in it.
The 2.3 gear was a great all around gear. Put plenty of pitch in the prop and went where i wanted no issues. It was a narrow gear and i broke a rooth or 2 in it. I bit into the 2.68 fever that was going around for awhile. It's not a good big block ratio if you make any kinda power. I added a lil pitch,and my cruise rpms went up about 500rpm and fuel consumption went up. Dont notice any differance in push as the boat did all i wanted before. I believe the 2.68 is a small block ratio cause they don't make the torque a big block does. In my opinion you'll be happier with a 2.3 gear. If you want to run a 5 blade with pitch in it you'll likely need a 3.something gear.
Compromise is for those that cant get it done!!

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Re: 4 blade vs 5 blade for heavy load

Post by Moritz » Sun May 28, 2017 11:19 am

I am running a 2:68 gear box 4 supper wide Blades 80" prop 5200 600 hp @ 5200 496 chevy big block. Pitch set on 1 7/8 on a 8 by 16 Gto 2400 # boat Runs great will run ground with 4 to 5 people guns dog and decoys no problem. Heavy load deep water and into 20 mph wind 4300, Cruise light wind 4100. Normal load 3500 to 3600 typical curse 26 to 28 on gps

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Re: 4 blade vs 5 blade for heavy load

Post by Moritz » Sun May 28, 2017 11:20 am

Heavy load is 3600 to 3800# total

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406 JAMIE
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Re: 4 blade vs 5 blade for heavy load

Post by 406 JAMIE » Sun May 28, 2017 3:44 pm

here u go i have about same boat 13'6 X 7'6 was runing a sbc gm crate motor 350/330hp with rotator gearbox 2.12 swinging a 3bld 79in whisper tip ex blds it did OK but once i threw my all steel bbc 414ci small cubed big blick oval port heads with a a 750dual feed holley mech secondary s.we got 500hp/trq on 87 oct regular gas 7-11 special lol lol and i used same prop and gearbox just added some more pitch in prop.and joe is wright about 2.68 gearbox for sbc.i would run the 2.37 rotator gearbox if i had to do it all over again.my boat was a 1998 deepsided hull diamond back.
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Swamp Thang
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Re: 4 blade vs 5 blade for heavy load

Post by Swamp Thang » Sun May 28, 2017 9:54 pm

Joe wrote:I've never put it on the dyno so I can't give definitive answers on torque and hp but it's right around 550hp. It has felber mild ported heads and his 496 cam in it.
The 2.3 gear was a great all around gear. Put plenty of pitch in the prop and went where i wanted no issues. It was a narrow gear and i broke a rooth or 2 in it. I bit into the 2.68 fever that was going around for awhile. It's not a good big block ratio if you make any kinda power. I added a lil pitch,and my cruise rpms went up about 500rpm and fuel consumption went up. Dont notice any differance in push as the boat did all i wanted before. I believe the 2.68 is a small block ratio cause they don't make the torque a big block does. In my opinion you'll be happier with a 2.3 gear. If you want to run a 5 blade with pitch in it you'll likely need a 3.something gear.
Thanks Joe, I've ruled out the five blade. Probably go with four S blades and stick with the 2.3 for now.

Swamp Thang
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Re: 4 blade vs 5 blade for heavy load

Post by Swamp Thang » Sun May 28, 2017 10:03 pm

Moritz wrote:I am running a 2:68 gear box 4 supper wide Blades 80" prop 5200 600 hp @ 5200 496 chevy big block. Pitch set on 1 7/8 on a 8 by 16 Gto 2400 # boat Runs great will run ground with 4 to 5 people guns dog and decoys no problem. Heavy load deep water and into 20 mph wind 4300, Cruise light wind 4100. Normal load 3500 to 3600 typical curse 26 to 28 on gps
Thanks for the info Moritz,I'm hoping the 632 will have enough torque to spin the 84" I will rarely carry as much weight as you, only two seats most of the time.

Swamp Thang
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Re: 4 blade vs 5 blade for heavy load

Post by Swamp Thang » Sun May 28, 2017 10:13 pm

406 JAMIE wrote:here u go i have about same boat 13'6 X 7'6 was runing a sbc gm crate motor 350/330hp with rotator gearbox 2.12 swinging a 3bld 79in whisper tip ex blds it did OK but once i threw my all steel bbc 414ci small cubed big blick oval port heads with a a 750dual feed holley mech secondary s.we got 500hp/trq on 87 oct regular gas 7-11 special lol lol and i used same prop and gearbox just added some more pitch in prop.and joe is wright about 2.68 gearbox for sbc.i would run the 2.37 rotator gearbox if i had to do it all over again.my boat was a 1998 deepsided hull diamond back.
Thanks Jamie, the Diamondback came with a 2.3 Century belt drive so I'll try that first but be looking for a 2.5 gear set to try also, the S blades don't like to spin fast. The main goal with this build is low rpm hp & tq to keep it as maintenance free as possible, I like riding much better than working on them.

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