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Why cant I bust 70mph?

Old 02-04-2002, 10:31 AM
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The worst prob with the older Scarabs (I had one) is the X dimention.
Wellcraft stuck those props/drives so deep down in the water that the drives create alot of drag. It's a big deal to raise so I suggest steps 1-3.
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Old 02-04-2002, 10:33 AM
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You have to think up until the mid to late 80's if you had an 80 mile an hour boat you were very very fast. Its not until recently that boats started running the speeds we are now. I wouldnt think a '78 hull has the technology to run that fast. 70mph aint too shabby amungst the general population, you just happen to be surrounded by freaks of physics with some wild ass rides.
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Old 02-04-2002, 11:25 AM
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You need a CAT!
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Old 02-04-2002, 11:31 AM
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NO **** Tantrum! Your right!

Let me tell you, besides when Im running you with rich ass nut baskets... I pretty much dominate everything...

Still... I just cant stand it that my boat runs 69MPH. There is just something WRONG with that... ya know what I mean.

Its like owning a bike that only does 198 mph... (which btw, I do... )

Why the hell do manufacturers build **** that is JUST short of the mark! Arggggggh (banging head on wall)

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Old 02-04-2002, 11:44 AM
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If it went 72 then your mark would be 75.

It is what it is. Be happy or be prepared to spend at least $1000 per mile per hour that you want to increase.
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Old 02-04-2002, 11:53 AM
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Hey nick, my dad had a 79 scarab 30 with 454's in it, I dont remember the speeds it did, but I thought it was fast back then, and never liked the slow cruiser scene after he sold it, I have pic's of it and I clearly can see how deep the drives are with his.With that said, I would have to side with DJD, with the x-dimention being about 12 inches below the bottom of the boat, where two inches would be a safe. But that's a big can o worms to change but food for thought. If the 70 barrier is your goal, picking up a set of newer risers and some rubber exhaust hoses, and tips and going thru hull, would probably be the best all around choice and most inexpensive, but have the advantage of a cool sounding boat too for the same price as props. I've done lots of prop testing and I dont think a cleaver would be a good choice due to lack of lifting the bow. A bravo one 4 blade would probably be the best bet, lots of bow lift with it and a big surface for getting up on plane, a hydromotive might work, but more stern lift than bow lift, and a small surfacre and not too great for getting a big heavy boat on plane, see if you can give some test runs with some oso members and try different prop combo's, take em out lobster hunting for thier troubles, Synthetics, would help too, but all depends what direction you want to go with this.

[ 02-04-2002: Message edited by: advantage_ROB ]
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Old 02-04-2002, 12:17 PM
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Your RPM's are too low. You should be at 5000. 300 RPM up top makes a big difference. Lab your props for $200 at Chad Hill and you will probably see a big difference. Don't you have TRS drives? I may be wrong but don't they eat some HP? Also check your carbs and make sure you are getting WOT. Remember this, once you break 70 you will want 75, then 80 then 85 etc, etc It is a vicious cycle.

Good luck
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Old 02-04-2002, 12:51 PM
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I'm no expert here, but I'd suggest a prop change. NOt sure if you're using 4 blade/3, whatever or what pitch, didn't see it. But, I'd shy away from labbed props if I were you. Only reason is you do a lot of diving, right? Those labbed props can get sharp and hate to see you slice your leg or something. You don't have the greatest luck, you know. LOL!

If you're running 24's or something, lets say, try a set of 23 or 22's. (have no idea what you run, but just an example) Might get your RPMs ups and you can test if that is a problem. YOu can maybe borrow some just to test before spending a lot of money. Try to get your RPMS to 4950-5050 somewhere.

You can check that out, and I bet some headers or other exhaust upgrade would help you. But that is pricey.

Like I say, no expert, maybe I'm wrong, tell me if I am anyone....I could stand to learn more too.


[ 02-04-2002: Message edited by: 32fever ]
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Old 02-04-2002, 02:01 PM
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Have you ever calulated your prop slip or check the bottom for a hook?
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Old 02-04-2002, 06:47 PM
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I ran your boat on my power vs. speed program with 8000 lbs and 380 prop HP. Are you using 25 Mirage props? With your weight and horsepower, that's the pitch I needed to get 67.9 @ 4700 RPM. I plugged in some upgrades to get some idea of what you could achieve. But before I tell you the results, we have to talk.

Why can't you just be happy with your current speed like the rest of us? Beware! This is what will happen to you if you are determined to break 70 mph.

First comes the better exhaust, which will give you about 69.4 @ 4800 RPM. Then working the prop to drop the pitch to 24, which will give you about 69.5 @ 5000 RPM. So close you can taste it. You have to have more! You will try every cheap trick in the book to push that boat over 70 mph. Finally, you realize that you must have more power!!

You will tear into the engines. You will get pissed off and put on a better set of heads to get 73 mph @ 5250 RPM. Broke through 70 big time, but are you happy? NO! By now you're hooked! A big hydraulic roller cam and you're up to 78 @ 5400. Then the blower, and you're up to 88 @ 6000 RPM.

It's no good. You can't stop yourself. You have to go faster! In a few years you will install a pair of 900SC and go 100 mph @ 6000 RPM but it won't be enough. You will have to put in a pair of Vortech supercharged Torque 1500 V-12s and go 128 mph @ 6000 RPM, after installing the 36" pitch five blades on your soon to be scrap VI drives.

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