HP Question

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digginfool
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HP Question

Post by digginfool »

I have a 15x8 Diamondback with a 465 HP Marine Power 496. Horsepower is never cheap and I don't particularly need any more now, but I may need it in the spring when it's a lot drier and running across lots of mud. Most of the time, I will be fully loaded with people and gear. Before I dump $7-8K for another ~100 HP, is it worth it? Will the additional power help that much or is it strictly bragging rights? I'm running a 3-blade 80" Power Shift, poly on the bottom. That brings up my next question; if it's worth the investment, what's the most effective means of putting that power to work? Increase pitch or diameter? I've read that an adjustable prop works most efficiently at its 0 position and loses efficiency as you increase pitch. I've also read that doesn't start to occur to any large degree until you get past the 2 position. How much horsepower are you talking with a (I assume) 2 degree change in pitch?
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Deano
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Re: HP Question

Post by Deano »

I see where you are going and understand the reasoning for it. You must have been a boyscout. :)

However, an accurate questimation of which way to go and how to get there would be contingent on info that we don't have yet.
We know you have a 465hp/496ci and an 80" 3 blade PowerShift prop.

What we don't know is what reduction, gear or belt ? What gear ratio is it ?
What RPM are you currently turning the motor?
Which PowerShift blades are you running ? Falcons (+-12") or Sirius (+-14" LH) or Maximus (+-14" RH)
What is the current pitch you have in the blades, to turn it at the above RPMs ?

Surely not meaning to be picky, but rather arrive at an accurate answer to your questions. Obviously there are a lot of considerations. There is a large degree of accurancy in your statements about the pitch marks in most cases. Some blades are differrent in that reguard. What may be littleraly true in one case, may only be close in another.

You have acquired a very nice rig for yourself, you are to be congratulated. :salute:
Now that you've run it around some, the only natural thing to do is "let the tweeking begin . . . " :thumbleft: :lol:
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digginfool
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Re: HP Question

Post by digginfool »

Thanks for the quick reply. I'm running a 2.38 Stinger. The chord on the blade is 14" and, looking from the back of the boat, RH rotation (I guess that makes them a Maximus). WOT I'm turning about 5150. Have no clue what pitch the blades are currently set at but looking at the center line of the hub to the leading edge of the blade, I would have to say pretty close to zero. Of course, especially with my eyes the way they are, I doubt I could discern a couple of degrees anyways. :wink:
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Re: HP Question

Post by digginfool »

Just remembered that there would be a white mark on the back of the blade. The mark definitely lines up with the middle of the hub.
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Re: HP Question

Post by junglecat »

great box , but for a 496 , horsepower of 465 is rather mild for todays standards. A bolder profile cam and good roller lifters could really bring that BB alive. Brother in law just finished a 496 for another member that rides with us. Its a conservative 600 + hp . Its on a 16 x 8 high side DB with 11 stringers/ walkarounds /poly . A very heavy boat and it runs like a tank on the hill with the same box you have.
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Re: HP Question

Post by digginfool »

junglecat wrote:great box , but for a 496 , horsepower of 465 is rather mild for todays standards. A bolder profile cam and good roller lifters could really bring that BB alive. Brother in law just finished a 496 for another member that rides with us. Its a conservative 600 + hp . Its on a 16 x 8 high side DB with 11 stringers/ walkarounds /poly . A very heavy boat and it runs like a tank on the hill with the same box you have.
I feel the same; I know there's more hiding in there. Raylar has their Stage II kit for ~$7,000.00 that has aluminum heads, cam, roller rockers/lifters, intake that makes 540 HP, or their Stage III for ~$8,700.00 that makes 607 HP, but also requires forged rods & pistons be installed. Then my installation costs go up dramatically. I can do heads, cam and intake by myself but not comfortable enough to take on the rotating assembly.
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Re: HP Question

Post by flying fish »

a 2.5 ratio box will help you on the ground.

I would think your combo is quite strong on the ground as is????
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Re: HP Question

Post by flying fish »

Talking Mud-
I have ran in silty mud that was so slick, I near lost all control of my boat. Slipping and sliding and near out of control.

Then in the same day a bit further up the river (above a lake), I ran into some mud that was greyish black in color. Looked kinda solid but was sun cracked with green sprigs of grass sticking up about 6".

This stuff was bad. 3 miles from nowhere and much silt between me and where I needed to go.

I had a strong boat. 500ish horse 434 with a 2 to 1 reduction and an 3 blade 80" powerplus. real strong combination. 14' boat w/72" bottom.Boat had 3/4" radius in the bottom at the midship brace. Real strong ground runner.

Back to the mud. Near threw me out of the boat when I hit this stuff. Pushed up in front of me like I had a bulldozer blade. Took me near 5 hours to get out of the stuff digging with my oar and listening to my wife tell me how stupid I was for being stuck.

100 horse have helped? IMO-hell no. Stuff was mean. Dig out move 3' dig out again. Glad I only had a short distance to get back to the water. I still think a helicopter could have gotten my boat out of that mess.
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Re: HP Question

Post by digginfool »

The muck we have here is like glue. It sticks to everything. My boat does have a cheater box with two spray heads but when all else fails, HP is king (so I've been told - but then again, so is cash and I hate wasting that :lol: ). I'm really not looking to go out of my way to see if I can get stuck but, come Spring, the area I'll be riding tends to have a lot of areas that are just plain nasty. Until you get there, you won't know what's waiting for you; skinny water or nasty muck.
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Re: HP Question

Post by coondog123 »

Where is my thinking wrong. Wouldn't a 2.68 gear box be the first place to start, then go with different blades then address the motor.
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Re: HP Question

Post by todd glover »

What type of 496 is it is it a 454 with a 4-1/4 crank if so lots of options if its a 8.1 496 the only heads you can get are dart make a set of heads and intake if its a 454 and not a roller you can make it a roller but a roller is harder on the valve train good luck do lots of research before you send a dollar good luck
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Re: HP Question

Post by Deano »

@Coondog - - -
Power is power. He has a very heavy (when fully loaded) boat. He currently only has 465 hp. More gear and different blades is not the answer for a lack of power, more power is. Simply can't escape the reality of the power/weight ratio.

The engine, gear ratio and the prop are all very well matched. With the engine turning 5150 and the 2.38 ratio the prop is turning right where it was designed to. This is a lot of prop by way. I would prefer to not alter such a well matched setup, either. Evidently the previous owner simply didn't see the need or have the desire to have more power. I'm sure there would be little or no need with a light or occasional moderate load.

@digginfool - - -

I am going guess the white mark on the blade shank matched the hub seem because it was put there as a reference mark after the fact. With the power you currently have, I would expect you can add a good amount of pitch before that became an issue. I don't think adding 100 hp would render that prop inefficient by any means. Probably could add more than that. If Andrew or Plumcrazy don't see this and weigh in, I would call them at WaterWalker and see what they say.

I agree with your assessment and what JungleCat eluded to, you can do a good bit of upgrading without having to get all the way down the rotating assembly. More power is exactly the way I would approach it. Those boys from White Performance have got stuff running all over the place up here and seem to be top notch. I would also contact them and get their assesment of what your options may be before I started parting with any money.
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digginfool
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Re: HP Question

Post by digginfool »

coondog123 wrote:Where is my thinking wrong. Wouldn't a 2.68 gear box be the first place to start, then go with different blades then address the motor.

Not questioning your knowledge but why would I want to slow my blades down? I can do that with throttle. And as far as blades, I'm already turning pretty large blades. I can only add inches (only two more inches available) or number of blades (I could go to 4 blades). Now if I do both (change gear box and increase number and length of blades), I've spent nearly the same amount of money but I've increased rotational loads with the bigger hub and higher number of blades. My ears are open. In some respects, I see your approach but on the other side, the parasitic loads of the bigger gear box and number of blades might only compound the issue. Now, to be clear, I'm not even sure I have an issue yet; haven't encountered any sticky mud yet with this boat. But from what I've been told, 2A and 3A can get really nasty when it gets dry. I want to slide, not dig, my way out. :wink:
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Re: HP Question

Post by coondog123 »

Deano thanks for the info. Diggin Fool my post was more of a question so I could learn. It is obvious I need to read more and learn more. My thinking was more along the lines of different gear box and then more pitch to the blades. More pitch, more air moved and then you get across the mud spots.
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Re: HP Question

Post by Prototype »

This might sound really stupid but have you thought about 2 props for your rig. One size does not fit all, and all does not fit one, but if you know what your getting into in advance you could bolt on the prop and pitch to run it?

I have been running two props for circumstances and need but I know wtf my day will be like in advance. You could make your boat a dozer or a semi speedy demon with just a prop change and nothing else!

It's just a thought that takes a little effort in fine tuning to each prop for your load?
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Re: HP Question

Post by Deano »

coondog,

Look at it like from the standpoint of 'where is the power band of the engine'.
Ie. Where does the engine make it's power (the most torque)?

For example: Take a wide blade prop that wants to turn at say 2100 rpms.
Engine #1 - 350 small block turns 5600 rpm, uses a 2.68 ratio = 2,090 prop rpms
Engine #2 - 500 Caddy BB turns 3700 rpm, uses a 1.77 ratio = 2,090 prop rpms

The Caddy makes torque low, the SBC makes torque high,
the ratio spins the prop where it is the most efficient and the engine makes its best power.
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Re: HP Question

Post by flying fish »

I do not know if you can get a hub to equal 80" in 4 blades using your current Maximus blade. You have an amazing propeller for low end push. Again, the 2.5 ratio will help you with ground running. A long hub will yield you an 82" 3 blade. 1" closer to the cage. 2" total length longer going to a long hub.


I would wonder if computer controlled, what is governing this engine. Prop or computer??

The topic engine is a 496. is this piece a Levitator?? :)
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Re: HP Question

Post by digginfool »

After a long weekend in the Keys, more questions. My target is the 600 - 650 HP range. It seems the easiest way to get there is with a supercharger. I was initially opposed to that route since the service load is so high with a supercharger. The engineer in me says otherwise but had a gentleman argue that a normally aspirated 650 HP engine sees no less load than a supercharged 650 HP engine; 650 HP is 650 HP. He went on to argue that a supercharged engine will be easier to manage once properly set up and would most likely be more efficient (that is, better fuel economy) at lower throttle settings. What experience has people had using low boost (say, 4 or 5 lbs) supercharging on airboats?
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Re: HP Question

Post by digginfool »

flying fish wrote:I do not know if you can get a hub to equal 80" in 4 blades using your current Maximus blade. You have an amazing propeller for low end push. Again, the 2.5 ratio will help you with ground running. A long hub will yield you an 82" 3 blade. 1" closer to the cage. 2" total length longer going to a long hub.


I would wonder if computer controlled, what is governing this engine. Prop or computer??

The topic engine is a 496. is this piece a Levitator?? :)
The engine is a Marine Power. They provided me with the spec of 465 HP based upon engine serial number.
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Re: HP Questiona

Post by T-REX »

How does putting in 'roller' lifters and 'roller' rockers
Make it HARDER on the valve train ?!!!
That's the first I've ever heard that one....
I could see making it a 'solid' lifter would be questionable..... But what's wrong with a
Hydrolic roller set up????????
I would think making the most of what you already have would be
Primary- before adding a supercharger....put some good efficient heads/cam/etcetcetc ....
Then if that's not enough...pressurize it!
Remember pressurized air adds heat.... So then a cooler is needed....
And all this adds weight!!
Good aluminum heads with supporting cam/ valve train .... Well now your LOSING weight!!!
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Re: HP Question

Post by flying fish »

digginfool wrote:
flying fish wrote:I do not know if you can get a hub to equal 80" in 4 blades using your current Maximus blade. You have an amazing propeller for low end push. Again, the 2.5 ratio will help you with ground running. A long hub will yield you an 82" 3 blade. 1" closer to the cage. 2" total length longer going to a long hub.


I would wonder if computer controlled, what is governing this engine. Prop or computer??

The topic engine is a 496. is this piece a Levitator?? :)
The engine is a Marine Power. They provided me with the spec of 465 HP based upon engine serial number.
Is your engine a fuel injected piece?? If so, what is governing your engine? Propeller or computer??

Do you have enough prop for your current engine or are you governing your engine with a computer?

I guess I can not figure out why the Levitators (fuel injected) engines that I am around will swing more prop than yours, and are just animals on the ground with near your exact setup???

Is your engine fuel injected and computer controlled???
Can the people that supplied you the horsepower # info also tell you if your engine is fuel injected and computer controlled?? :)
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Re: HP Question

Post by digginfool »

There are several posts on here regarding good design parameters for airboats and almost universally, the rule of thumb is 3 - 4 lbs of boat & gear per HP (I did see one suggestion of 4 - 6 lbs per HP). If you consider my boat, it seats seven and has the 496 BBC (8.1 Vortec) with gearbox and prop. There are five in my family with a total weight of around 650 lbs. If I fill the seats, I could easily be up to 850-900 lbs. Add 50 pounds for cooler, ice and drinks, easy 500 lbs in running gear and not even counting the boat I'm at 1,400 lbs. I have a 40 gallon fuel tank and, when full, adds another 240 lbs (not counting the tank). I figure hull and rigging has to be in the neighborhood of 1,000 lbs so I'm looking at fully loaded weight around 2,600 lbs. Conservatively, I should be running 625 HP. I only have 465 HP. That is sufficient for my purposes right now, although the boat is a bit sluggish getting on plane. The water is deep everywhere and I don't have to worry about running on the ground. Come Spring when the water gets real skinny to non-existent, I don't want to be in the middle of the Everglades shoveling mud to get my boat moving again. It's simple as that. Before they outlawed it, I used to run my four-wheelers out there and I have first hand experience on just how nasty the muck is. The people I've met out there have also told me to be very careful come Spring (or anytime the water gets real low) because of how tough it can get. One gentleman I know said he hit some mud out there once and it stopped his boat cold; threw him right out of the boat. For what it's worth, the engine is EFI.
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Re: HP Question

Post by digginfool »

BTW, even though Marine Power says the motor is 465 HP, the people at Raylar said that the motor came from GM rated at 420 HP and somebody at Marine Power most likely figured the headers added 45 HP and marketed the engine as having 465. They doubt it has much more than the OEM rating of 420.
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Re: HP Question

Post by digginfool »

blackwaterairboats wrote:Your motor should truly be a 425hp and 500 torque. I have had two of the same motors the only difference is mine were a pleasure craft marine motor. My new motor is 607hp and 664 torque my boat is 18x8 and holds 9 people plus me and holds 50 gals of gas. My boat will run 80mph and will go just about anywhere.
I know. Your boat is my inspiration. :thumbleft: You've seen my crew, you know my boat and we both run the same area. I want the same kind of flexibility as you have with your boat but trying to figure out the best way to go. I've been talking to a company that specializes in using the Whipple but it's starting to sound like he's hesitant to recommend it for an airboat. So, it's looking more and more like I will be going with the Raylar Stage III to get my power.
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Re: HP Question

Post by flying fish »

Seems you have your mind made up. Cool.


For what it's worth........... Possible prop is not governing your engine.



Possibly if you put 2 warp drive blades on your boat @ 80" you might still be governing her @ 5150?? :)

There are (2) 18' boats where I run with the 8.1 Levitator. Both swing more prop than you have and will run dry with 6 or 7 grown men and a 150 quart full cooler and 50 gallons of fuel. They are both animals on the ground. The 425 horse and 500 torque rating on the engine is way conservative when talking prop swung. One of these boat is a 18' Airranger. A way strong ground runner.


You have a real small boat with lots of power. Your money.

I guess by now (maybe) you have figured out that I think you have a remarkable power plant.
I realize there are haters out there, but again, you have a really amazing engine/propeller package coupled to the 2.3 ratio.

I really question whether or not your engine is being governed with prop. If you were to take the propeller off your boat will she rev past 5150 RPM???? :)

If you are going to go with a 600ish horse BBC that is carbureted, you are moving a long ways backwards in the game. Again. JMO-
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