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Discussion Starter · #1 ·
Hope you don't mind my asking but had some questions about the boat I bought off of you.

You stated in previous threads the boat ran 67 mph on the GPS with a 21 pitch Mirage Plus prop with your 502 motor. You also stated it had the rough epoxy bottom paint that is on there now (when you achieved those speeds). I don't know what rpms you were running, but those #'s sound like very low prop slip.

I am running very high % prop slip and was wondering what I am doing wrong.

I am running a stroked 496 with 177 blower, dyno'ed at 531 hp at 4 psi boost. Will up boost (to around 600 hp) after good break in. Top speed I can get with bravo 1 24" prop is 52 mph at around 5000 rpms full WOT. Something like 28% prop slip.

I haven't tried a mirage plus prop, but did try a 14 1/4 X 23 Ballistic prop which just blew out, not enough dia. I think.

I see the Mirage plus 21 pitch is 14 3/4 prop, but I don't think the 21 pitch will be steep enough but maybe the extra .5 " would keep it from blowing out. Any thoughts?

I know you said the bottom paint was on there, so I don't know what else could be causing such drag on the boat. I was thinking maybe the trim tabs are angled down too low (even when retracted all the way), maybe that could have a bearing on it???

Any thoughts Norm?
 

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Discussion Starter · #2 · (Edited)
Oh, I've checked some for sale adds and saw a video on you tube.... most of the Andretti's out there say they'll run in the 60's with a 454. So what the hell is going on... is it the 4 blade prop? Before the old 454 blew, I tried to run the ballistic and couldn't even get enough rpms to get on plane.... now with the 496 it just blows out right before getting on plane.
 

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Sounds to me like you need more dia. & pitch.
I run with a SS Apollo 14-3/4 x 21 behind an Alpha with only 270 hp. but I'm only pushing 3000lbs.
But I would think a Bravo with 600 hp should easily be able to handle a larger dia. prop.

What did Julie at throttle-up recommend for you.??
 

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Discussion Starter · #4 · (Edited)
She recommended the Bravo 1 24" pitch to start, and I bought the one I'm using from her.

However, I'm getting a lot of slip and I was thinking since I have a low drive, maybe a 3 bladed prop? The 4 blade 24 pretty much throws the boat out of the water (especially with the extra torgue of the stroker motor) but it doesn't rev to the range I built the motor (5500 rpms is where I want to max).

I'm at work (yeah I know on the 4th but that's a cops life) but will post a pic of the tabs... I'm wondering if they hang too low... which would cause drag

BTW, the Bravo 1 prop is a 15 1/4" prop, a full 1" dia larger than the ballistic I was blowing out, so definitely a larger dia prop is needed, but I was wondering if the 3 blade would be better but can't keep paying $500 plus for props to play with so wanted some opinions before I buy another. Will also try used on ebay or here.


Fyhr Factor said:
Sounds to me like you need more dia. & pitch.
I run with a SS Apollo 14-3/4 x 21 behind an Alpha with only 270 hp. but I'm only pushing 3000lbs.
But I would think a Bravo with 600 hp should easily be able to handle a larger dia. prop.

What did Julie at throttle-up recommend for you.??
 

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OK, lets see some pictures of the tabs in a level position, then of your drive lowered and keel together in one shot, and a close up of the bottom coating you were taking about..
I figure the more eyes on it the better..to see what your dealing with.
 

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Discussion Starter · #6 ·
Okay, I'm get some pics today after work. Too dark now and I'm getting ready to go. Hope it stops raining in PA soon too.... :rolleyes:
 

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Discussion Starter · #8 · (Edited)
I don't think Andretti's 502 was stock, but he never mentioned specific HP details. He also never told me the rpms he ran. But I think 67 with this boat with a 21 pitch prop would be incredible...

A deep v boat will have slip, but shouldn't be above 10-15% I'm double that right now.

I'll get some pics of the bottom paint, it might account for some slip, but not 10-15% I wouldn't think.

Some day I'll weigh the boat on some truck scales... you know, boat and trailer, then just trailer to figure out how much the boat weighs. The boat new was supposed to be arund 5000 lbs, now probably higher with age (soaking water etc)


Not Right said:
67 with a stock 502 sounds way off, especially with bottom paint :confused:
 

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Discussion Starter · #9 ·
I'l like to find a good used (or try one free) Mirage plus 23 prop. I'd like to get my WOT rpms near to 5500 rpms, this motor is complete roller and should easily handle the rpms. Besides, the faster I spin her, the more hp the blower should make....but the torque peaked around 3900 rpms if I remember correctly.


Tack said:
With that much HP, you should easily turn a 23 or 25 Mirage plus, maybe a labbed 25. Or consider a 26 labbed or stock 24. 29scarabthunder puts out about the same HP on a 29' scarab and he turns a 26 worked prop. Good luck and keep playing with it. Way off from where it should be. See if anybody has any spare props to borrow to try, then go from there.

Tack
 

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Discussion Starter · #11 ·
Cool thanks. I think that will be over propping it, but I'll still try it.

Maybe I can just grab it from you one day at Blue Marsh. I'm dying for a ride in your 80 mph boat anyhow :D

I'm pulling my heads tomorrow to have them looked at, something is making a slapping noise and I want to be safe, not sorry...


cookin said:
Adam,I have a 27p mirage for you to try.Call the restaurant and pick it up.215=679 7700
 

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Hey Adam.

Yes that boat did run 67 with the 502, but I'm sur that it was in right conditions like 2 foot chop, by myself and low fuel but it would do it. It would do a consistant 65 with ease anyway. I don't understand your mid 50's. The motor was built, but I couldnt tell you anymore about it ,cause it was the way I bought it. That motor would turn up 5800 and scream. I did bang the rev limiter a couple times and it hit 6000 out of the water. That small 21 prop did its job. The coating has alway been on the bottom. I hated it but it was there from previous owner. I tried a few different props...been a while but as I remember a 23 dropped the rpms down considerably and as well the speed. I don't even know if that 21 prop I had was labbed or not, but it worked the best out of all I tried. I really don't think the tabs are an issue.
Hope you work it out, it was really a fun boat.

Here is a vid of it running on calm river with the 502. This pass was mid 60's with the 21 prop on it.

Andretti river run
 

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I was running a mirage plus 3 blade stainless on a 2452 arriva with a 502 carb engine with 24 inch pitch. engine was around 450 hp, prop slip 18% with tabs at 1/4 down drive trimmed pretty high and LOW on fuel I got 72 gps. took 5150 rpm to get there. try the mirage plus prop, it is a stern lifting prop and will probably help. 24 pitch will get you in the range you want to be. just my .02 worth but i did a lot of prop swapping and found it to work the best on my hull.

snivley
 

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Discussion Starter · #14 ·
I wonder if I should try running the tabs down with more trim on the outdrive? I don't have to trim much with the Bravo 1 24" prop before I start to porpoise.

Thanks for the replies... I'll try the Mirage Plus line of props...
 

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Discussion Starter · #15 ·
Norm, thanks for responding... I can't view the vid because of my supporter status (I'll have to buy something) but I remember it from before. Cool vid and I would like to add it to my you tube account if you wouldn't mind.

I'll try the stern lifting props, maybe the Andretti's *** is too fat LOL
 

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1adamb said:
Some day I'll weigh the boat on some truck scales... you know, boat and trailer, then just trailer to figure out how much the boat weighs. The boat new was supposed to be arund 5000 lbs, now probably higher with age (soaking water etc)
Can you show a current photo of your boat in the water from this year, at a similar angle and distance Andrettii is showing in the video post above, I just want to see if she sits at the same waterline.
You have must have some kind of drag somewhere, I'm just trying to figure out from what.

Here's just as an example of a non- speed boat,

I once had a similar length, 9 ft beam, but was an old wood deep vee boat that weighed 5,000 lbs bone dry, add 1,500 lbs. loaded, it drafted 3 1/2' of water docked. it had a 302 sbf I had built (about 300 hp), w/na 650 holley, Big Merc IO, turning an 18-1/2 dia.x 28" 3 blade alum prop, it did 32 knots (35-36 mph) at about 3000 rpm at sea. per my Loran, (GPS wasn't around yet)
Of course I could of changed the prop for more speed, but it wasn't a speed boat and not my goal on that boat.

My point is, it shows you what a little 302 small block can do turning a very large prop, so with your BB SC 600 hp engine, 65+ mph should be easily reached with your hull. it's just trying to figure what's holding you back.. :confused1
 

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Discussion Starter · #17 ·
Actually I don't have a single photo of the boat in the water.... will work on that.

If I remember the video correctly (still can't view the above) the Andretti has quite a rooster tail going on, due to the prop being high up. I don't get that effect with the prop I run.... I like the idea of the mirage plus lifting the stern out of the water more... maybe that'll solve my problem.
 

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1adamb said:
Actually I don't have a single photo of the boat in the water.... will work on that.

If I remember the video correctly (still can't view the above) the Andretti has quite a rooster tail going on, due to the prop being high up. I don't get that effect with the prop I run.... I like the idea of the mirage plus lifting the stern out of the water more... maybe that'll solve my problem.
Yes, it does have a decent rooster tail, and looks like he's trimmed way up..
 

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i dont know if i can help or not but my andretti will run 62 on gps with the mirageplus 23 lab finish i got from tach if im not mistaken the prop came from julie i hav a bone stock half tired 454 i would think you need a 25 3 blade or a 27 labfinished a four blade will not give you mph with that hull all it may do is give you a better cruising speed
 

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Discussion Starter · #20 ·
Hey red, thanks for the responce. That makes me feel better... I'll definitely look into it and reply back. I have to get my motor back together though (having the heads gone thru again!!!!!)


red andretti said:
i dont know if i can help or not but my andretti will run 62 on gps with the mirageplus 23 lab finish i got from tach if im not mistaken the prop came from julie i hav a bone stock half tired 454 i would think you need a 25 3 blade or a 27 labfinished a four blade will not give you mph with that hull all it may do is give you a better cruising speed
 
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