New prop help

Airboat propeller discussion.
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Lighten
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New prop help

Post by Lighten »

I have 16x8 Alumitech 3’ rake full deck over setup for bowfishing( lights, generator, front steer) 1/2 ploy bottom, its heavy. The boat and tandem axle aluminum trailer weight 4780lbs, 3/4 tank of gas. It has a 509 BBC edelbrock heads with sniper efi, roller rockers, ch-3 2.3to1 that about all i know about the motor, it barely will run dry with WOT 5150 and cruise is 3800 with driver only and 1/2 tank. Turning 4 blade sensenich 79” K series around 1 1/4 mark. I mostly want it to run dry easier and cruise better with a load, i know i need updated props, do i need more motor also? Is the pitch they are at less than what it should be. I know my prop is way outdated and i have no clue what h.p. the engine, is any help is appreciated.
16x8 Alumitech 509 BBC ch3 2.3-1

unforgiven11B
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Re: New prop help

Post by unforgiven11B »

That K series produces max thrust @ 2800. You are leaving a good 500-550 RPM on the table. However if your engine is not capable of higher rpm then set it as closely as you can to the cam specs max Rpm. I twist a 81” 3 blade K series @ 5500ish WOT w/ch3 2:1, cruise at 3200-3500 (23-28)mph give or take. 16x8 deep hull SS rigging and she’s heavy runs dry all day.

Lighten
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Re: New prop help

Post by Lighten »

What engine are you running and HP and what pitch are you set at. I don’t know if my engine is low on power or i need to get a 3 blade hub. All my cylinders are 180 on compression +/- 10
16x8 Alumitech 509 BBC ch3 2.3-1

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digginfool
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Re: New prop help

Post by digginfool »

While I certainly wouldn't discount the knowledge of most people on this site, you will never find more knowledge than the folks at Sensenich and Whirlwind. They've seen every combination imaginable and are an enormous free resource. Since you already have one, I would start with Darren at Sensenich.
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Lighten
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Re: New prop help

Post by Lighten »

I have talked to someone there, dont recall there name. They feel like i may be down on power. I have checked everything i know to check on the motor. It doesn’t burn oil or use coolant runs good, sounds good, timing is at 36* WOT, a/f ratios are good also. Iam at a loss kinda.
16x8 Alumitech 509 BBC ch3 2.3-1

barhopper
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Re: New prop help

Post by barhopper »

I would try a three blade. Sounds like to much prop for the motor to me. A higher ratio would also help. The other thing to check is the bottom of the boat. Make sure there are no hooks. That can make all the difference.

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OneBFC
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Re: New prop help

Post by OneBFC »

Lighten wrote:I have 16x8 Alumitech 3’ rake full deck over setup for bowfishing( lights, generator, front steer) 1/2 ploy bottom, its heavy. The boat and tandem axle aluminum trailer weight 4780lbs, 3/4 tank of gas. It has a 509 BBC edelbrock heads with sniper efi, roller rockers, ch-3 2.3to1 that about all i know about the motor, it barely will run dry with WOT 5150 and cruise is 3800 with driver only and 1/2 tank. Turning 4 blade sensenich 79” K series around 1 1/4 mark. I mostly want it to run dry easier and cruise better with a load, i know i need updated props, do i need more motor also? Is the pitch they are at less than what it should be. I know my prop is way outdated and i have no clue what h.p. the engine, is any help is appreciated.
My vote is power issue combined with a whole bunch of weight. seriously, that's a big load.

But, power solves all problems except a high fuel bill. And I think your down some, somehow.

As a reference, though you didn't mention prop diameter or I missed it, my little motor can turn a 4blade 80 inch Falcon on the 2 setting 5400 on the trailer with a 2.38 ratio. I would think a 509BBC would obliterate a 4 blade K at that low of a pitch.

Hope you find a solution!
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-----------------------------------
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unforgiven11B
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Re: New prop help

Post by unforgiven11B »

I’m running a PCM/Levitator 6.0 published numbers state 375hp@5xxx and 366ft/lbs TQ, personally think they are over inflated for my model year. The new 6.0’s are 409hp and on dyno pull pretty close last I seen. I’m a 1/16” shy of the 2 mark on blade pitch. Dropping a blade might get you where you need to be. If sensenich thinks your down on power and everything checks out on your end you may have too much prop just haven’t seen a 509 not want to twist 4 k’s I’ve seen a few Spinning 4 r’s/ 4 ex’s

Lighten
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Re: New prop help

Post by Lighten »

Thanks for the help guys. This boat has been like this since i bought it used this year. Iam gonna pull the cam to see if there is any numbers on it, iam guessing its the factory hydraulic roller, has pretty high manifold vacuum at idle. Anyone know a good cam grind for a 502bbc? 5300 max rpms
16x8 Alumitech 509 BBC ch3 2.3-1

Gary S
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Re: New prop help

Post by Gary S »

Lighten wrote:I have talked to someone there, dont recall there name. They feel like i may be down on power. I have checked everything i know to check on the motor. It doesn’t burn oil or use coolant runs good, sounds good, timing is at 36* WOT, a/f ratios are good also. Iam at a loss kinda.
I know this seems silly , but you sure your getting full throttle? I have seen it before.

Lighten
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Re: New prop help

Post by Lighten »

Yes its getting full throttle and all the air/fuels ratios are good on the sniper efi.
16x8 Alumitech 509 BBC ch3 2.3-1

SeatCover
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Re: New prop help

Post by SeatCover »

E85 and a blower should solve the problem. Maybe a bigger fuel tank?
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Lighten
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Re: New prop help

Post by Lighten »

Prop diameter is 82” and cant really go any bigger. Would the superwide 3 blade possibly push better?
16x8 Alumitech 509 BBC ch3 2.3-1

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kwanjangnihm
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Re: New prop help

Post by kwanjangnihm »

Lighten wrote:Yes its getting full throttle and all the air/fuels ratios are good on the sniper efi.
is it possible to have good air/fuel readings and still not get enough fuel to max the system out?? (not pressure, but volume) :scratch:
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One Eyed Gator
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Re: New prop help

Post by One Eyed Gator »

My old boss had a mild 454 (cam and work to stock heads) on a 15x8 alumitec, he turned a 80'" 3 blade K with a CH3 2:1 prop was set at 2. He had to run it 38-4000 to keep it on plane. Had 1/2 poly heavy rigging and cage live wells. Always seemed to struggle.

Superwides are designed to turn slow using a 2.55 or 2.68 ratio

Cheapest route would be to buy a 3 blade hub and try putting more pitch in the 3 blade setup.

Also what kind of wire does it have on the cage some of the alumitec cages have expanded metal on the them reducing the air flow.

Lighten
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Re: New prop help

Post by Lighten »

It has 4x4 holes in the cage, no expanded metal.
16x8 Alumitech 509 BBC ch3 2.3-1

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