Scorpion Prop Question

[Trueser]

2000 28ZX Scorpion.
377 Hp
1.5 Ratio Bravo XR
25 Pitch Mirage Plus labbed
5200 RPM

The best I have seen was 80 on Livorsi GPS speedo.

At that speed and RPM it should be less than 2% slip. does this sound correct?

[VetteLT193]

Mirage plus is a cupped prop. Everything I have read says to add 1 inch to the prop calculation for props with a cup.

That puts you at 6%, which is still excellent. :wink:

[BigGrizzly]

That slit is way too small. You need to multiply by 2 +20% which puts you between 5 and 7%. Remember you have 2 props not one and the drive drag is theoretical a 20% factor loss.

[mjw930]

That slit is way too small. You need to multiply by 2 +20% which puts you between 5 and 7%. Remember you have 2 props not one and the drive drag is theoretical a 20% factor loss.

Randy, that doesn't make sense. If the drive introduces a 20% loss then the maximum theoretical speed assuming 0% slip would be reduced thus making the numbers he posted even more unlikely.

Example, 5200 RPM, 1.5:1, 25P = 82.07 theoretical 0% slip speed. His calculated slip is 2.52%. If you reduce that by 20% because his theoretical 0% slip number is reduced due to the extra drive you end up with a calculated slip of 2.016%.

Am I missing something?

Regardless, if his numbers are correct, and I have no reason to suspect they aren't, he's getting all there is to get from his combination regardless what math we apply. Whoever labbed those props did a pretty darn good job.

[BigGrizzly]

No, I must have stated it backwards the second drive has a 20% sacrificial loss. for instance a single with the same HP will be faster in theory. Now for the final thing he very well could be at his max speed, at least with that combination with out more thinning of the props. A different style may produce more speed but it would not be worth the price. Me I would like better handling then one more MPH. But still 2% slip is not a realistic number with that prop.

[mjw930]

No, I must have stated it backwards the second drive has a 20% sacrificial loss. for instance a single with the same HP will be faster in theory. Now for the final thing he very well could be at his max speed, at least with that combination with out more thinning of the props. A different style may produce more speed but it would not be worth the price. Me I would like better handling then one more MPH. But still 2% slip is not a realistic number with that prop.

Got it, thanks.

One things for sure, either the prop was repitched, the tach is off or the GPS is off because I agree, 2% slip with that prop and that boat is highly unrealistic. I would be thrilled with 10% slip.....

[Trueser]

Props were just scanned and the are 24.780 and 24.197 . New Livorsi GPS speedo that was accurate. And Teds old boat same props runs 84 GPS.

I agree on the stability with a 4 blade and plan on trying more for everyday use.


So if Teds old boat runs 84 what would his slip be? same configuration except Stainless Marine and no Mufflers.

[mjw930]

Props were just scanned and the are 24.780 and 24.197 . New Livorsi GPS speedo that was accurate. And Teds old boat same props runs 84 GPS.

I agree on the stability with a 4 blade and plan on trying more for everyday use.


So if Teds old boat runs 84 what would his slip be? same configuration except Stainless Marine and no Mufflers.

NOT turning 5200 RPM he ain't!

The absolute maximum speed you can get from a 25P prop is 82.07 MPH turning @ 3466.67 RPM (5200 RPM through a 1.5:1 drive).

Something believable would be 5600 RPM and an effective pitch of 26P. That's 9% slip and a number anyone would be happy with considering your higher X.

[VetteLT193]

Theoretical speed (0% slip) with a 1.5 ratio, 25 inch cupped prop, @ 5200 is 85.

[Trueser]

Rev limmiter set at 5250 and you can hit it.

[mjw930]

Theoretical speed (0% slip) with a 1.5 ratio, 25 inch cupped prop, @ 5200 is 85.

Regardless, that has to be a magic set of props because no matter how you twist the numbers the efficiency is better than I've seen setting up race boats.

BTW, I still have a hard time believing a relatively box stock 28ZX with 377's running 84 mph but that's just me. Remember, if you are running in a river or anyplace with a current and wind you need to run in opposite directions and average the speed.

[VetteLT193]

Regardless, that has to be a magic set of props because no matter how you twist the numbers the efficiency is better than I've seen setting up race boats.
BTW, I still have a hard time believing a relatively box stock 28ZX with 377's running 84 mph but that's just me. Remember, if you are running in a river you need to run in opposite directions and average the speed.

I was just posting the baseline. I hear ya.

[Trueser]

Both boats will be at AOTH this year. I think if I added stainless marine and no mufflers I will be close to 83-84. Ted has always said that his boat was the fastest 28ZX ever built.

I would say that my tachs and GPS speedo are correct.

I will have a ride for you at AOTH!

[BigGrizzly]

Just remember there was nothing stock about Teds props. Ted never abused that boat, I ran with him at Eufaula and I know it goes over 80 but by how much I could not say. One small minor point he does know how to drive to maximum potential.

[VetteLT193]

Both boats will be at AOTH this year. I think if I added stainless marine and no mufflers I will be close to 83-84. Ted has always said that his boat was the fastest 28ZX ever built.

I would say that my tachs and GPS speedo are correct.

I will have a ride for you at AOTH!

and you could have a tach that's a bit off, say 2350, and you are dead on speed wise, slip, etc. for anyone that wants to pound on the numbers

who cares anyway if you are having fun. you'll pass me for sure.

[mjw930]

Just remember there was nothing stock about Teds props. Ted never abused that boat, I ran with him at Eufaula and I know it goes over 80 but by how much I could not say. One small minor point he does know how to drive to maximum potential.

That's what I've been saying, that number stamped on the side is meaningless.

I know what you mean about every boat and driver being different. I pissed off a lot of Velocity owners as I passed them running a smaller prop and a smaller motor.....

I guess my take on this is Trueser has a really sweet running ride and I wouldn't change a thing.

[FISHIN SUCKS]

.......and sweet ride it is:yes::yes:!!!! Throw some Enzyte at the motors and see if that makes a difference Mike. W/my twin 350's, I am thinkin' about it.

[BigGrizzly]

930, the T man is happy, he just likes to tinker and stir the pot(he spends too much time wit Road Trip):yes::yes::wink:

[Pismo]

Since your prop is labbed the true pitch could vary greatly.

[BigGrizzly]

He had them scanned. I am sure his numbers are and average of the blades on each respective prop. So the pitches are with in the STD. tolerance for props. I am surprised that the difference is 0.5 inches difference on labbed stuff. I do know that it is really difficult to reverse engineer a prop to be left hand.

[Trueser]

Tinker LOL

This is my plan. Take Teds old props that will be comming to AOTH with his old boat. and have them scanned, take one of my sets and have them matched to his.

And I will let Grizz And Fuzzy drive my boat at AOTH....

I also attached the prop scan for your pleasure.

[roadtrip se]

930, the T man is happy, he just likes to tinker and stir the pot(he spends too much time wit Road Trip):yes::yes::wink:

He started digging into that boat the day he got it...

Mike, don't forget that skeg too, while you are looking at things...

[BigGrizzly]

I also think that ted had low water pickups and I don't know if yours does. as for driving With our weight fuzzy is correct. Don't get me wrong I am definitely NOT turning down a ride in that boat. The scans show you that no two props are the same. It also shows you cannot copy exactly especially left to right. I will say I am surprised that these boats actually go that fast, but am sure they do.

[Trueser]

All good, I do have low water pickups. We will need to still do some see trials.

:nilly: