24 Speed Update
 

We took her out for the first time this year yesterday. The lake was calm and pretty smooth. I still haven't changed props, so i'm still running on the labbed 25P Mirage plus. Once I get the 27P on, I think we'll see the real numbers. We hit a best of just a hair under 76. Speedo pic included. More updates to come!

Very nice. How much HP do you have?

501hp @ 5200 rpm

What are you turning that 25? I'm still running a 23 on my Pantera and think a 25 would be the ticket. (I'm turning the 23 upwards of 5700-5800. ;))

It's turning close to 5400 rpm right now. It is in perfect shape with no nicks or anything. It will be for sale once I test and like my 27P if you're interested. It is a very nice prop.

Zeimer, remember peak HP is in the 5800rpm range.
That's where you should be topping out at.
Unless that's up against the limiters.
You could always try a 25, or even have that labbed.
Chasing those last few mph can drive a looney.:drool:

Jayhawk, what kind of torque and where in the rpm range?
Those are some nice #s.

Peak torque is 535.7 @ 4629 rpm, and it's at or above 500 lb*ft from 3627 rpm to 5253 rpm. It pulls like a beast!

I'm really hoping to break 80 with the new prop. I haven't put it on yet cause it is a pain in the ass to do on the lift without help, and ,y wife isn't strong enough to help out. My engine builder is making some fine tune adjustments to the computer program, and when he brings that down we will swap the prop and get the new number.

I'd try a Bravo 1. A 24 Super should run 80+ any day of the week with 500HP. I can hit 78+ on most days with 425HP. I'm turning a 28P @5000 rpms.

I don't know if it's true or not, but some people say that you run faster in salt than in fresh. Are you running in salt or fresh Dave?

My boat has always responded better to a three blade prop. Any of the four blade props I've tried made the boat feel sluggish and handle poorly. I don't know if it is the X dimension or what makes that happen, but the 3 blade always works better. That being said, if I can put my hands on a Bravo 1 28, I'd certainly like to test it. I can't find anyone who has one though.

Another problem I am having with speed is that at WOT and trimmed out, the bow feels planted, like it isn't lifting out of the water. Whether that's the case or not, I can't say for sure. That's just how it feels. If I'm not getting enough bow lift, that would probably scrub a little speed as well.

I run in both salt and fresh, I don't really notice a speed diff.

As far as the bow lift, when riding in the boat it doesn't feel like the bow is lifting all that much. But, when I look at a running pic, you can see the bow is lifted enough to let the boat run on the pad. I find that I don't need to trim my boat much above neutral to get top speed.

My boat came with a 25P Mirage +, the handling was terrible. The prop broke loose in rough water and I chine walked a lot. I switched to a 26P Bravo 1 and the speed was the same but the handling was MUCH better.

Listen to Dave, he has the same boat as you.
The 3 blade may be a tick or 2 faster but the boat will handle better with a 4 blade.
Bolt on a stock 28p B1 and test vs. the 27p M+.
80mph should be no problem with 500CSHP.

I definitely plan to try one out when I can get my hands on one. I'm not ruling it out for sure!

Well, I ran the 27P Mirage+ this weekend, and I couldn't pull the rpms. Just to get close to 4900 rpm, I had to trim to the moon and then it got way squirrely. trimmed up about where the 25 Labbed was, the most rpm was about 4700, and about 74 mph.

That being said, I doubt if I could turn the 28 Bravo. Is my X too low maybe? the engine makes the power. i saw it on the dyno myself. This is dyno that is historically stingy as well. There has to be something wrong with the set up.

Any thoughts anybody? I think I may have the 27P labbed to see what I can come up with on it. I guess we'll see.

Hey Dave, do you know what your X-Dimension is? if I have yours to go by, I'll measure mine and see if we're the same there.

Thanks!

Not really sure. I can attempt to measure it later when I get home.

When Sean Dutra owned that boat she ran about 74mph with a 25p M+ and 72mph with a 26pB1.
That was with the stock Merc 385HP/454MagMPI turning 4900rpm or so.
He added the headers and did not gain much except she sounded meaner.
I ran with Sean 3-4 times and had many conversations about our 24 Superboats before he sold the boat 4-5 years ago.
The boat was always a tick or two slower than Dave's but with 501HP she sould run over 80mph regardless.
Compare the prop shaft depth with Dave and test a 26p B1.
You may also want to check for a hook in the last 4 ft of the bottom. My Superboat did have a hook but it did not seem to slow her down.
Good Luck and be Safe.

whats a hook?

A concave area in the bottom near the transome.

Thanks Dave. I hope it isn't an inconvenient thing for you to do. Correct me if I'm wrong, but the X is the distance from the keel to the centerline of the prop. If I'm wrong, let me know. I just want to be sure we are measuring at the same points.

Hey Pat, by the time I got the boat, the best I saw with the 25P M+ was 72.0 at about 4800 rpm. I spoke with Brett at BBlades, and he thinks we can add a little cup and maybe even a little pitch to the 25 and get some more mph that way. It has already been massaged a little by him last year, so he knows what it is at this point. I may see if I can get my hands on a 26 B1 and see what the result is.

As I understand it, a hook is a gradual turning down of the fiberglass at the stern on the bottom surface of the hull. As far as I know, this is usually caused by sitting on a trailer with bunks that are short of the transom and it overhangs. The weight of the back end of the boat will slowly deform the bottom of the hull where it isn't supported. I will check for this, but the trailers it has been on and the lift I have all overhang the back of the boat so it should not have had an opportunity to sag. It is possible though.

Thanks again for the help!!!

JC alway thought my old 24 would be able to pull a 26labbed... not a chance.
Find that prop that will let u right up to your max(5200) rpm w/o hitting the limiter... that's the trick.
Try a 26b1. I wouldn't spend the $ labbing anything till you try all stock props.

Btw, i ran w/ sean my 1st summer w/ the boat(with the stock 454) and I wouldn't say he left me in the dust. I was running around 64-65.

Here's a few pics, I'll email you the high res files.

Pic 1 This measurement was 6.25", from the bottom of the transom assembly to the bottom of the "V" on the pad.

Pic 2 This should at least give you and idea if your x is close to mine. I took this pics with the propshaft parallel with the bottom.

Thanks Dave! I'll look for the bigger images in email today. I wasn't able to measure anything this weekend as we had some company down for the weekend. Now that I have this though, I can get some measurements and compare.

Looking at the straight on pics from the rear, I'm not sure if we look much different from memory. I'll let you know what I find out!

Thanks again!! I owe you a few beers for sure!

Well, I measured mine at the same place as you Dave, and mine is 6 1/2". That means that I am 1/4" shallower than you. I doubt if that would make much of a difference. I suppose I could try a small spacer to get the drive a little deeper. Might be worth a shot. Heck, it's cheaper than a shorty!

measure from the pad to the center of prop shaft, most vees with a deep drive will be 6 to 8''. my baja was about 7'' ,now with a 2'' shortie I am at 5 and pick up better handling and 4 mph. so even if your at 6 to 61/2 go a 2'' shortie and 4 blade 3s won't work my buddy has about 575hp in his 24sb with a trs way to deep it chine walks after 72 and has hit a high of 76 at 5600rpm with my old 25 mirage. hope this helps and pat hows the new boat. artie

I realize it's a TRS and all. But something does not sound right there. I can hit 76 any day of the week with 425HP.

The prop is at the right height if it's the same as Dave's.
Try a 26p B1 or a 25p Rev 4. You want your max rpm at 5200-5300.
These boats are vary weight sensitive so to get max speed you will need to set her up to run with no tabs, 1 person (just the driver), 1/4 tank or less of gas.

The 76 was with 2 people and at least a half tank of fuel. I may be getting my hands on a 26P Hydromotive Quad IV-X to try. That is supposed to be their bow lifter prop. I can't seem to get my hands on a Bravo 1 of ANY size! I've been looking to try the 26P Bravo 1, but can't find one short of spending $300+ for something that may or may not work. I already did that with the 27P Mirage+. I need to put that up for sale now.

BBlades says he can add some cup to my 25P and get a couple more mph, so I may try that as well. I guess this is the downside to having a hot rod. The upside is that the engine runs fantastic. It starts and runs like a new merc motor and sounds bad ass. We did a little tweaking to the program and that helped with cleaning up the idle and some starting issues. Some of the timing numbers were way off what they should have been. My engine guy went through the program box by box and cleaned up all of the discrepancies. The original programmer didn't take care of the small stuff in the program.

Hey J,
My boat ran 1mph slower for every extra person/150lbs.
BBlades has B1 and Rev 4 test props.
The QIV-X is similar to a B1 but on my old boat the B1 was faster.
I plan to rebuild my 454 vary similar to yours. I have an HP500 cam and HP500 heads in my stockpile. I bet your program would work. Are you using a MFEI-3 computer? Did you check the program in the boat with O2 sensors? Can your builder load my little black box?

No O2 sensors in the boat. When I get my tails re-done or get new ones, I will have them set up with the sensor fittings so we can check it. My tail pipes need to be re-done because the exhaust ports on my heads are 3/8" higher than stock. We've got them on, but it does leak just ever so slightly.

Brad can do MEFI 3 computers. That is what mine is. The work he has done on mine is just the tweaking. Tyler did all of the A/F ratio work when the engine was on the dyno. We had to send it back and forth several times as Brad didn't have the software for MEFI computers at the time. He finally bought it after my engine was done. I used Tyler's cam, and his program specifically for the cam was WAY off. The first start up was so rich that no one could go in the dyno room without choking on rich gas fumes!

I don't know how much Brad would do for a computer for an engine he didn't have on his dyno. He is VERY careful about things like that and likes everything to be just right. He has had engines pop on the dyno that had a program that was set up "just right" for the application by someone else (whipple), so I don't know if wants to do long distance tuning or not. It would certainly be worth a call though. I'll probably see him this weekend as well and can ask what he thinks. You can PM him as well. He is Nobody on the board.

The last time I did a cam swap and computer changes to one of these engines the outcome was not all that great. I had use AZSpeed to reprogram and reprogram and reprogram, but in their defense, I did not use a cam they had done before.
The next go around, I will definitely have an O2 sensor to check the air fuel ratio while running the engine under load in the boat. The ignition timing would be something I hope has been worked out for the HP500 cam.

he never had it dynoed so it could be 525 to 575, I sold him my old heads intake and the cam was the 731 crane I believe. like I said his is deep plus fat trs plus tranny = 76 all day long he has owned it for 16 or 17 years and its had a stock 330 to a gale banks twin turbo 454 in it, now a 502 with dart, nick 850 ,cmi exh heads rec with work 731 crane= teage stage two cam. your boat has a hire drive height no tranny, step? that adds up. he can mash the throttles at a standing start which we can't do other wise it a new coupler or drive:p. and he needs ex steering the chinewalk gets bad real quick if he hits a wake or wave. I told him to convert it but he won't.

We tried the Hydromotive today. It is a new Quad IV-X 26 P. We first ran on the 25P Mirage + with the BBlades lab work. With 2 200+ lb guys and between 1/4 to 1/2 tank of fuel we hit just over 74 at about 5300 - 5400 rpm. With the Hydromotive, we got about 75 at about 5100 rpm. The Hydro was a little faster than the M+. The best thing about it was that the boat finally felt like it came up out of the water and got on the step. The hydro prop mad the boat feel more like I think it should. I'm REAL eager to try a 26 B1 or a labbed version of the Hydromotive.

Also, I may be switching over to a carb to get the rest of my power. I really think this stock intake (my engine guy does as well) is kiling the power. He wants to try an 830 with a brodix type intake and see what we can do with that.

Here's a little video from yesterday's run. Lots of wind noise and bouncing. It's our first one, so hopefully we'll get better.

http://www.youtube.com/watch?v=G9D5bkgwr-8

Randy, sounds like you like the bow lift. Put a carb on dat thing and go fast. Brian

Yeah, it definitely felt more "right" with the Hydromotive. The bow lift was there. Now we may have gotten more speed than we did with some better water. We made our first runs with the 25 Mirage + with just a light chop. By the time we changed the prop to the Hydromotive, the water had gotten a bit rougher and we couldn't maintain the speed over the bigger waves. I'd bet if we ran it first, we would have seen another mph or so. I'm guessing with just me and low fuel, I'd see 78 with the Hydromotive. How soon do you need it back Brian? I'd like to test it a couple more times in different conditions and see how it goes. A labbed version of that may be dead on.

Thanks for the loaner!

Hi Randy,
Did your engine dyno 501HP with dry headers or with wet exhaust like in a boat?
Did you dyno with long tube headers or short like your CMIs?
If the exhaust used when you dyno'd is not the same or vary similar to what you're running in the boat, your engine is not making the same power in the boat.
It is sounding to me like you have more like 450HP in the boat. If you had 500HP in the boat you could spin a 28p B1 to 5100-5200rpm and run over 80mph.
As for the Merc MPI Intake; it is adequate for a 500HP 460cube engine. There are many guys that are using them on 525HP 502cube engine with success. There are also proven mods that shorten the runners for better flow if you like.
I would agree that switching to a carb and high rise intake is a lot easier to tune and get that last bit of power out of the engine though.
If you do pull the EFI stuff off, shoot me a price for the goodies. I plan to build a 450+HP 454 this winter.
Have fun and be Safe...:cool:

Hey Pat, the engine was dynoed with long tube dyno headers. Other than that, all accessories including raw water pump were in place. I think we can assume we're losing some power due to the difference in headers as I'm sure it likes the long tubes much better for scavenging.

That being said, I may pull it again this winter to do something more powerful. We will most likely keep it for another couple of years at least, so I'm going to try to have some fun with it.

The reason we're leery of the intake is that the power curve goes flat at 5200 rpm. You could hear it on the dyno. My engine guy built a 502 with a similar cam/intake/head setup, and it went flat in the same manner at 4800 rpm which makes sense being that it is more cubes. After running in the boat, they switched over to a single plane and an 830 and were able to nail the rpm and get a fair amount more power. He hasn't dynoed it since the change, but he feels it made a drastic improvement.

Yup, the engine with dry long tube headers is definately going to make more power than the short wet exhaust in the boat. Don't know if it's 50HP, but your top speed numbers are the same as I had in my old boat and vary similar to what Dave gets with a 425HP 496 in his 98 24'.

The water mixing in will the exhaust hold it back as much as anything. I've done some testing with a bud with an engine running with a cross over and no thermostate. The more water we dumped outside the exhaust the faster the boat went, that was also with Stainless Marine manifolds not headers.
It sure does sound like the MPI intake could be a bottle neck.
I've read that the Merc intake is good to 5200 on a 502 stock and even a 540 with porting/shortened runners.
I bet if you went for a bigger cam in your engine along with a carb and high rise instead of the MPI you could easily gain 50HP.

Randy, Go ahead do more testing. Just remember, your taxing your drive and probably getting the drive pretty warm. Just keep an eye on it. I ussually spin those at59 to 6300rpm. Say hi to your wife for us. Brian