60 plus mph with 21p vengance?

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60 plus mph with 21p vengance?

Postby chambers1517 » Sun Jul 06, 2014 7:29 am

I have a 2008 interceptor evidently I am hitting the rev limiter at 5000 rpm. I have hit exactly 55.38 mph at 5000 rpm. I get an alarm and lose power until I slow way down. I have done it 10 times this week and as soon as I hit 5k it is done. What rpm are you guys turning when close to 60. Maybe my rev alarm is set too low. Maybe I have prop slip. I can hit the rev limiter with some throttle left. I'm stumped. I can run 4950 rpm all day but 5000 immediately gives the alarm.
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Re: 60 plus mph with 21p vengance?

Postby iammarcuse » Sun Jul 06, 2014 9:51 am

Sounds about right. But you didn't say what motor you have. Rev limiter on a 5.0L is 4950, a 350 Mag is 5080. A 5.0L would have a hard time spinning a 21 Vengeance to 5000 rpm... and will never make 60 mph. Most of the 350s came with 1.50 gears and so they won't hit the limiter either. Check your drive and see what gear ratio you have. It is stamped on the side. I doubt the prop is spun as you likely have a flo-torq hub on the vengeance.
By contrast my 6.2L has 1.65 gears and I can spin a 21 Vengeance to 5200 and still be shy of the 5350 limiter.
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Re: 60 plus mph with 21p vengance?

Postby chambers1517 » Sun Jul 06, 2014 10:45 am

I'll check the drive gear ratio later. I have the 350 mag. I would probably be ok with a boat full. I am also considering a rev 4 because we do a lot of tubing and the vengance seems to blow out easy. I just can't figure out how people get 60 mph with a. 21p prop without overreving.
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Re: 60 plus mph with 21p vengance?

Postby iammarcuse » Sun Jul 06, 2014 11:42 am

Chances are you have a 1.50 Bravo One which 'usually' works with the 21 Vengeance. If you go with a 21 Rev4 you will not hit the limiter but you will not gain any speed. A 22 Enertia would be the best of both worlds if you have the 1.50 case. If you have a 1.65 Bravo or 1.62 Alpha you should consider a larger diameter prop like a 22 Tempest Plus.
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Re: 60 plus mph with 21p vengance?

Postby chambers1517 » Sun Jul 06, 2014 12:10 pm

Thanks. Ill check the gear ratio. It is a bravo drive.
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Re: 60 plus mph with 21p vengance?

Postby buyfire » Tue Jul 08, 2014 10:58 am

chambers1517 wrote: I just can't figure out how people get 60 mph with a. 21p prop without overreving.


I can't say I've seen anyone hit a true 60 MPH with a 21P prop, that would most likely give you a negative slip percentage, which isn't possible. Maybe a wishometer reading, but never on a GPS with a 1.50 drive. A Bravo and a 1.50 should get you to 54-55 MPH at 5000 RPM with a low slip percentage.
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Re: 60 plus mph with 21p vengance?

Postby chambers1517 » Tue Jul 08, 2014 2:12 pm

I got exactly 55.38 on gps before the alarm sounded a cut power. Should I worry why I get an alarm at 5000 rpm and is it possible I am over reving. I heard there should be no alarm for over rev just a loss of power. I can't understand why the alarm start at 5000 rpm everytime.
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Re: 60 plus mph with 21p vengance?

Postby iammarcuse » Tue Jul 08, 2014 6:40 pm

I didn't think there was an alarm either but it seems to make sense since it happens as you go over 5k. Your actually rpm and what the tach says are not necessarily the same thing. I know my last motor was about 200 rpm off a shop tach. Nevertheless, normally the rev limiter simply causes the engine to slow down by reducing spark timing.

55-57 is about what you would expect with a 350. Don't forget you will be faster in cool weather or at sea level. Not many seeing 60 with a 5.7L. Mine runs 60 but I have a 6.2L which is 20 more ponies. With a Vengeance I see 58. See if you can find a 22p prop to try and see what happens.
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Re: 60 plus mph with 21p vengance?

Postby AndrewT » Tue Jul 08, 2014 6:51 pm

My 212 with 270HP VP and a 21P 3 bladed prop(VP prop) topped out at 55mph at sea level, cool conditions, 1/2 tank of gas and only 2 people.
Confirmed with a GPS
http://www.youtube.com/watch?v=q2fZR3TXp9c
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Volvo 5.0 GXi 270hp
21P 14.5 3B SS prop and 19P 4B SS for wakeboarding and tubing.
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Re: 60 plus mph with 21p vengance?

Postby chambers1517 » Wed Jul 09, 2014 10:12 am

I spoke to a prop shop who seemed to know their stuff and he is willing to work my prop or let me try a different one. He has some Mirage he would consider trades on. Anyone tried one of these? He also said factory props were very inconsistent with pitch. He said he sees lots with pitch off by 1 or even 2. A local shop has quoted $95 to read the codes but I hate to spend it only for a hi rev alarm. It bugs me too not knowing for sure. What do you think to start with, Prop exchange, prop work or have the codes read? The boat shop said they are a week behind and I need to get in line.
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Re: 60 plus mph with 21p vengance?

Postby buyfire » Wed Jul 09, 2014 10:50 am

I'd start with verifying that your tach is reading correctly. Last I knew, the recommended max RPM on a 350MAG was 4800-5200.So the rev limiter shouldn't kick in 'till after 5200 RPM. Is your engine the carbed 350, or the EFI 350MAG? Is there a possibility that at 5000 RPM there isn't enough oil in the pan to pick up, causing the alarm?
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Re: 60 plus mph with 21p vengance?

Postby iammarcuse » Wed Jul 09, 2014 11:27 am

Somewhere in the late 2000s they raised the rev limiter from 5080 to 5350 when they raised the rpm range to 4800-5200. Not sure what a 2008 has. If the later, then 5000 is where you want to run. Try another prop see if the problem goes away.

Don't bother getting a Vengence prop worked, it is an entry level SS. Depending on the gear ratio I would try a 22 Enertia, 22 Tempest Plus or 21 Mirage Plus. I run a 23 Mirage and it does very well for me but I have a 1.65 drive. Best speed and cruise and decent holeshot. Get about 4900 rpm and over 60 mph. Here are what the other props do. viewtopic.php?f=14&t=6440
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Re: 60 plus mph with 21p vengance?

Postby chambers1517 » Wed Jul 09, 2014 1:42 pm

Thanks, I think I will take my prop and trade it for a 21 mirage, If that isn't enough prop I can trade it for something bigger.
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Re: 60 plus mph with 21p vengance?

Postby sdk » Sun Jul 13, 2014 8:41 pm

58 mph by GPS is my best with the Vengence 21
2005 Caravelle Interceptor 232 BR SS
350 MAGMPI, Bravo 1
2014 Stingray 2LT Coupe
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Re: 60 plus mph with 21p vengance?

Postby msorenso » Mon Sep 22, 2014 8:30 pm

Do they still make the vengence? I didnt see it on the website b ut maybe I missed something
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