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flying tomato
01-10-2010, 06:55 PM
Alright guys. I know there are about 100 variables, but- - - - - -
What is the best prop for top speed on a Donzi Hornet III

Weight is approx 3300 lbs (Total)
TRS drive
500 hp bbc (496 cid)

Turbo 14.25 x 24 = 70 mph (gps) 5400 rpms
Mirage Plus 14.5 x 25 = 65 mph 4800 rpms
Bravo I 15.25 x 22 = 65 mph 5350 rpms

I know there's lots of experience on this site. Thanks in advance!!

Flying Tomato

MOP
01-10-2010, 07:36 PM
I will give you the same advice that any knowledgeable guy up will, get your butt to an event. There are always a few props available to try, there are even a few that will have several (Calling Big Griz) to try. You need to get at least close before dropping $$$$$$$$$$ that can get very expensive.

Phil

mrfixxall
01-10-2010, 07:36 PM
Alright guys. I know there are about 100 variables, but- - - - - -
What is the best prop for top speed on a Donzi Hornet III

Weight is approx 3300 lbs (Total)
TRS drive
500 hp bbc (496 cid)

Turbo 14.25 x 24 = 70 mph (gps) 5400 rpms
Mirage Plus 14.5 x 25 = 65 mph 4800 rpms
Bravo I 15.25 x 22 = 65 mph 5350 rpms

I know there's lots of experience on this site. Thanks in advance!!

Flying Tomato

If it were my boat i would send the turbo out to my prop guy and have it labbed :)

Planetwarmer
01-11-2010, 12:31 AM
I asked the same question a year ago, and most of the folks recommended the Turbo 1 for my 87 22C

oledawg
01-11-2010, 05:47 AM
I love to see this question pop up, which it does often! I have Mirage 27p on my '88 22c with 454 MAG and GPS is right at 65 at 4,300-4,400 rpm. I have put a labbed 23p on it during the winter spendfest and have yet to try it ( way too cold for this old man! ) so I have no idea what the GPS will be. The rpm's certainly should go up to around the 5,000 range and hopefully will gain some speed. Supposedly a 25p is just about perfect for this setup but everytime I find one at a decent price it disappears before I can get my hands on it. However I am a VERY patient guy! :pimp:

mattyboy
01-11-2010, 07:17 AM
what might be a good prop for a 22c might be not so good for a hornet III.
the hulls are different. wider flatter bottom alot of drag need to get it up and out of the water

FT,

the work is all on you of the 3 props which do you like best? what rpm range do you want?? what drive ratio

how is cruise , planning time, handling??

something seems off on the mirage from the turbo does it have a lot of cup??
for going up 1 inch in pitch and .25 in dia 600 rpm is alot to loose.
these all 3 blade ??

if you like the way the turbo handles and you don't mind spinning the motor over 5500 I might think about Fixx's suggestion. Phil's idea isn't bad either

mrfixxall
01-11-2010, 10:31 AM
what matty said is true,somthing just dont add up with the mirage prop. with my calculations you should be spinning that prop around 5100 rpm's

i gave you good advise in the past to get wheer your at rite now so here's some more.call my guy ( he seems to best in my eye's at labbing props for the boats i work on, i have always seen gains from 2-6 mph in his work) so box it up and send it to http://www.dahpropellers.com/.. call john and talk to him first so he can get a idea on what you want out of your boat..look at my vid,thats a volvo with a ultra prop with a bent prop shaft..:)

On the mirage try over trimming it,they like to be trimmed almost to a point of slipping the prop..ive seen gains on my buddys baja in excess of 5 mph slipping the prop..

BUIZILLA
01-11-2010, 10:51 AM
what matty said is true,somthing just dont add up with the mirage prop. with my calculations you should be spinning that prop around 5100 rpm's a big 10-4 on that advice..

BigGrizzly
01-11-2010, 12:38 PM
Yes I prefer the Turbo, but I sell them. Big BUT somethig is wrong here, the M+ should be turning about 5000-5200 RPMS. If you like the M+ swtick with it after you run 4800 with both props and find out the Turbo is better then stick with it. Oledawg, The 27 is too much prop and is not a good option the RPMs down. the 23 is to small, unless labbed bigger. Now a 24->25 would be my choice. Now that opens another can of worms--Which one!!! Some like the TXP some Like the Turbo1, in handling. With seat time the TXP is my favorite. It does take a little more driving experience. Also( AGAIN) I am not a fan of labbed props. Some work good and some don't. I don't care how they do it on OSO, or SOS, or what ever.

flying tomato
01-11-2010, 05:38 PM
Yes, I agree that the difference between the turbo and mirage was huge. I was very suprised!! The only thing that made any sense was when I put a tape measure on the Turbo. Even though it was stamped 14.25 diameter, my measurement was 14 even or even a little less. My measurement on mirage plus was 14.5 on the nose. So, I'm thinking that a 14 x 25 would be just about perfect.

Does anyone know who makes a 3 blade 14x25?????

Flying Tomato

72Hornet
01-11-2010, 05:50 PM
I just wanted to add my 2 cents to the question. Big Grizz was a great help to me on my Hornet with the Volvo. He even sent me two props to try and I was amazed by the difference in the two props that I kept them both! I know that the Volvo is a completely different application, but the message that I wanted to convey is that Grizz knows his stuff!

oledawg
01-12-2010, 02:27 AM
I am certainly no expert, but BigGriz is likely 100% correct that a 25p is going to be my best prop, just gotta find one. The 23p that I haven't even tried yet was a $50 purchase from a guy on this site. He even through in a couple of DONZI vinyl decals! Thought that I had a 25p Mirage + from Flyingtomato but it got away way too fast. Still looking for one in the $150 - $200 range. The 27p that I had runs the boat up to 65 gps with the motor WOT at under 4400 RPM. Like I said I haven't tried the 23p but agree that it may be too little prop for a 400 hp engine. :bonk:

BigGrizzly
01-14-2010, 11:01 AM
Tomato, be careful on how you measur the props because there are two diameters for turbo the small for smaller boats which I have never used. and the standard turbo which is as stated providing it has not been refurbished by a prop shop. In turbo you won't fins any wher that big of a difference between two props.

Greg K
01-14-2010, 12:01 PM
Which Model Turbo, since the Turbo 1 does not come in a 24 pitch.


Alright guys. I know there are about 100 variables, but- - - - - -
What is the best prop for top speed on a Donzi Hornet III

Weight is approx 3300 lbs (Total)
TRS drive
500 hp bbc (496 cid)

Turbo 14.25 x 24 = 70 mph (gps) 5400 rpms
Mirage Plus 14.5 x 25 = 65 mph 4800 rpms
Bravo I 15.25 x 22 = 65 mph 5350 rpms

I know there's lots of experience on this site. Thanks in advance!!

Flying Tomato

BigGrizzly
01-14-2010, 01:47 PM
The turbo does come in a 24, but not common very few were made.

NJFASTECH
01-14-2010, 03:58 PM
what might be a good prop for a 22c might be not so good for a hornet III.
the hulls are different. wider flatter bottom alot of drag need to get it up and out of the water

FT,

the work is all on you of the 3 props which do you like best? what rpm range do you want?? what drive ratio

how is cruise , planning time, handling??

something seems off on the mirage from the turbo does it have a lot of cup??
for going up 1 inch in pitch and .25 in dia 600 rpm is alot to loose.
these all 3 blade ??

if you like the way the turbo handles and you don't mind spinning the motor over 5500 I might think about Fixx's suggestion. Phil's idea isn't bad either

The Bravo I is a four blade.

Tomato how do the blades on the Turbo vs Mirage look Thinner,sharper are they close it sounds as though the turbo may have had some work.
Also what are you looking for extreme top end,cruise how do you boat full fuel,full boat all these things factor in dialing in a prop on a boat.You also have to test the props under equal conditions,fuel,weight,wind etc. BTW all of the numbers stand up to a classic prop calculation.

flying tomato
01-14-2010, 06:19 PM
njfastech,
Looking for top end speed. Trying to squeeze out all the mph. I am not sure which Turbo model I have. (no stamped model name or numbers on it--just the yellow "turbo" sticker)

The turbo blades are much thinner than the M+.

Note: I have taken the M+ to a prop shop and had them take off 1/4 inch off the diameter. Soon as the sun comes back out, I will be testing and posting the results.

Flying Tomato

NJFASTECH
01-15-2010, 07:05 PM
njfastech,
Looking for top end speed. Trying to squeeze out all the mph. I am not sure which Turbo model I have. (no stamped model name or numbers on it--just the yellow "turbo" sticker)

The turbo blades are much thinner than the M+.

Note: I have taken the M+ to a prop shop and had them take off 1/4 inch off the diameter. Soon as the sun comes back out, I will be testing and posting the results.

Flying Tomato

Again you need to dial a prop to your needs do you generally boat with 4 or 2 people on the boat? you may need a couple props to fit your individual needs

GeneD
01-22-2010, 07:02 AM
I used to be the salesman (me and Julie) for Throttle-Up Propellers. They used to be my racing sponsor.
One thing that has not been mentioned here, and is very important, is the RPM at which the camshaft reaches it's maximum HP.
Once you determine this RPM, you take the results of your testing and match propeller to desired RPM.
Soo...what is your camshafts max hp and at what RPM is that achieved?
I have a custom made Throttle-Up labbed Bravo prop on my boat that is fabulous. Cut down, labbed, and re-pitched. Took 3 months to get it right. I'm a huge fan of the Bravo, makes the boat ride super smooth and stable. And this prop does just that and allows the boat to achieve max hp at WOT.

BigGrizzly
01-22-2010, 10:09 AM
Gene I beg to differ with you, As an engine builder it is not just the Hp but the Torque as you already know I am not a fan of labbed props because of the cost vs the gain, in some cases Labs are not as fast or handle as well as out of the box props. I have proved this at several Rally s. The the best prop is not always the fastest prop for the application. At certain speeds the boat is too hard to drive. I have been there and done that. I have helped in the design of several props and have to make several changes to get them right. It took you 3 month to fix a prop that should have been right out of the box. Now you don't have a Bravo but a throttle up highly modified prop that is a one of a kind. The Bravo is the most modified prop in the industry. Why do you think that is? Not trashing the Bravo because it works great in a lot of applications. The max HP of my particular engine is at about 6,500. the torque is decreasing, after 4,500, so at 5,700 it won't pull the biggest prop at a speed above high 80s. When a smaller prop is put on to achieve the 6500 Rpma the boat is slower at top speed and is almost uncontrollable.

GeneD
01-22-2010, 12:44 PM
BG, there is of course that, to consider...:bonk:
Just relating what I was taught. You'll have to take that up with Matt!
How about this though:
The Chevrolet engine is the world's most modified engine. There has to be a reason for it.
Grizz, I know you're the man when it comes to props. I don't think there is actually one method of prop selection, there are lot's of combos available to us all. Matt was always coming up with different tweeks to fit different situations with different props. He's a very talented guy in this area.:checkered:
I don't think one brand is better than the next, just different. Merc props are mass produced and as such are subject to loose specs. We've always found Bravos out of the box were off on pitch on at least one blade. And...it's so heavy! But the Bravo prop is an excellent design that lends itself to easy modification to fit the boat's hull design and engine HP.
ie: More bow lift, less bow lift, less slip at hole shot, more slip at hole shot, more RPM, less RPM...
And I could be wrong with this, but I'm pretty sure I remember Matt saying that torque is a value whose power is utilized during hole shot and acceleration. Max hp is what allows you to get max speed. I'll have to confirm this next time I see him.
The prop on my boat is custom made, I wouldn't want it any other way. I took a prop with a pitch that I wanted to use and made it work. The 3 months it took was spent testing the boat every couple of weeks, taking and comparing data, wait for prop tech to get time to do mods, actually doing the mods, re-test...blah, blah, blah.
Maybe there is a prop out there that would do exactly what I want it to do, right out of the box. How would I know? I haven't tried all the props available out there!
Prop testing would be the way to go.
But you never really get exactly what you want.
That is why blueprinting and custom tweeking is vital for overall performance. I compare it to a finely tuned engine. We would all like to have our engines run great out of the box, but only with a speed tune will it ever see it's full potential.
It's kinda like putting your prop on a dyno!:cool!:
Whew!:blub:

oledawg
01-23-2010, 08:52 AM
eBay has a new RH 48 74604A 4 25P Mirage up for auction. Being a novice on props question is "will this work on my Bravo One", ie just bolt on? I have a labbed 23p that I haven't tried yet and the Mirage 27p that came with the boat. Thoughts? :pimp:

Cuda
01-23-2010, 10:02 AM
I had a three blade 24" Turbo on the 22 C that Howard has now. I tried several props, and it handled best with the 24 Turbo. It was a 454/TRS combo.

BigGrizzly
01-24-2010, 11:00 AM
Gene there is nothing left to be said. These guys are not pure race freaks but want the best prop for their wallet. Btw the reason for the chevy modification is because there are millions of them and you can buy parts all over. Between the old 283 to the 400 block most of the theories hold true.

oledawg
01-24-2010, 11:23 AM
Definitely a "sweet spot" in the HP vs torque curves, and although I certainly can't come close to being an expert in anything, my experience with cars and moto's says that in general big torque at less than max rpm = quick hole shot and max HP at WOT = top end.

I think that the bottom line in this is that there are so many variables involved that other than a starting spot, finding the "right" prop is using a true expert to get you in the ballpark, then trying some things in your environment.

GeneD
01-26-2010, 08:11 AM
BG...True dat!

NJFASTECH
01-26-2010, 07:58 PM
I have to be honest here I am what grizz considerers a race freak. Some guys settle for oridnary good performance with stock hardware that said there are props that can get a few MPH without engine mods. On my 353 fastech with some labbed 29 4 blade hydros from throttle up I was seeing 83 gps over the 30 pitch BI's formula supplied getting 79 mph GPS I did however put a set of 27 five blades stock on the boat that ran 80 gps and never got the chance to lab them but loved the way the boat came on plane. Now the race set up was completely different on the 29 FI fountain we had several props for different conditions I can say that my 25 hydro 4 blade chine walked out of control at 76-78 pull it through 80 and trim it out to max and it was on a rail.

Walt. H.
01-26-2010, 08:48 PM
Back in 07' I spent around $500. at Throt/Up to have a Merc Laser Labbed and the difuser ring cut off with hope of tweaking another 1-1/2 mph more out of my Alpha ss thats on my Carlson cvx-18, but instead I lost a good 3 mph and all driveability to stay on plane at slow/lower cruising speeds without having the prop blowout unless I kept the drive trimmed all the way down.
The prop sure looked pretty but I was glad I had another stock Laser 13-3/4"X25" to get my 3 mph back and my mid range cruise speed back w/o the prop blowing out shaking the crap outta my transom.
I know most times Labbing/blueprinting a prop works, but not everytime and for me I fell into the not everytime group..:cool:

GeneD
01-27-2010, 06:54 AM
WaltH,
In '07 I wasn't working there!
There is definitly something wrong with your combo.
What did Throttle-Up say about it?
NJFASTECH,
Wow! 4 MPH is great!

MOP
01-27-2010, 08:19 AM
I have to concur with Randy about reducing RPM to get into the torque range, when I first put the Bravo on my 22 383 SB all I had on hand was a 21 3b Merc wheel. It spun over 5K and netted 63MPH, I grabbed a 23 cleaver cheap it turned 5050 and netted 65 I knew I was on the right track. I bought a 4b Turbo Ultima strangely I only lost 50 RPM but netted 65.5, I am tempted to either add a tad of cup or a little more pitch to see what that might do. Like Randy says it is all about getting into your torque range, forget where peak HP is!

Phil

Walt. H.
01-27-2010, 10:58 AM
WaltH,
In '07 I wasn't working there!
There is definitly something wrong with your combo.
What did Throttle-Up say about it?


Hi Gene and thanks for the inquiry,
Julie said: "send it back to her and we'll add some more cup to it, you won't gain anymore speed but it should help with reducing some of the blowout."
Well that cost me some more UPS postage again but Julie did pay for the return trip, the added cup really didn't help anything, it just cut a minor amount of rpm's without helping or doing anything else.

I don't have any complaints cause going in having this work done I knew it was a gamble, sometimes you win and sometimes you lose when you attempt to make something good even better.

Thanks again,
Walt

Walt. H.
01-27-2010, 11:36 AM
I have to concur with Randy about reducing RPM to get into the torque range, when I first put the Bravo on my 22 383 SB all I had on hand was a 21 3b Merc wheel. It spun over 5K and netted 63MPH, I grabbed a 23 cleaver cheap it turned 5050 and netted 65 I knew I was on the right track. I bought a 4b Turbo Ultima strangely I only lost 50 RPM but netted 65.5, I am tempted to either add a tad of cup or a little more pitch to see what that might do. Like Randy says it is all about getting into your torque range, forget where peak HP is!

Phil

Phil,
If you need to reduce rpm's do it with additional pitch not cup, you'll gain mph at the same time with pitch not with added cup. Addition cup will just reduce rpm's and will assist in holding water bite better while swinging a tight turn and re-entering after jumping a wave..

For the average pleasure boater a regular prop repairshop will recommend added cup verses increasing the pitch to reduce rpm just because its the cheaper less expensive way to go, outside of just buying another propeller.

But in our hi-perf case we want to run the most pitch we can and still stay within the mid to upper rpm power range for maximum speed.

Manytimes with light hull boats i'll recommend dropping some diameter and adding it to the pitch which usually allows you to maintain the same exact rpm but results with increased speed because the smaller dia prop is easier to turn which would have resulted with increased rpm but by going up 1-inch in pitch cancels that out by increasing the same load on the engine and another inch of forward movement in theory before we factor in slippage.

As you once said: "prop testing is not an exact science but an experiment in progress"....
WH

GeneD
01-27-2010, 12:18 PM
From my archives:
How to Choose a Prop
The optimum propeller selection for your particular application is one that
will allow your boat's engine - with your normal load aboard - to develop full-
throttle RPM within the engine manufacturer's recommended maximum RPM range.
Every engine manufacturer states that range as part of the engine
specifications. Damage to the engine can occur if a propeller that allows the
engine to over-rev (attain a full-throttle RPM higher than the specification) is
installed. Damage can also occur if the installed propeller causes the engine
to lug - not reach the minimum specification. Overall best acceleration and
top-end speed will be achieved when your full-throttle RPM is near the
midpoint of the manufacturer's recommended maximum RPM range.
No where on any of my texts does it mention torque.
Go the the Mercury prop selector. It never mentions torque.
Go to ANY prop selector on the net, not one of them mentions torque.
What they do mention is the recommended operating range of the engine.
And ALWAYS...this number is where max HP is achieved.
You guys do what you think is best.
I'm done!:bonk: