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600hp Dissapointed top speed and take off!

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Old 07-21-2011, 10:22 AM
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Default 600hp Dissapointed top speed and take off!

What's up guys! I have a 1989 Carrera 24ft. With a 502 punched out to 509 est. 600 HP. I did not build the engine so i don't have exact specs of build. The problems I am having are frustrating me. Of course first thing that comes to mind is a prop problem... I have tried 4 different props. The one that works best for me is a Rev4 21p on a bravo 1. Rpms are at 5100 but top speed is only 60mph gps trimmed out. I do live in Utah at an elevation of 4500ft. I would really like to get 65 to 70 out of it. Motor runs like a top so It's not a problem with tuning.

The second problem I am having is prop blowout. When i go to plane out if i gas it at all above 2500 rpm until I plane the prop blows out rpm goes up and boat slows down. I tried a 21p mirage plus but it got worse so i am thinkin maybe a 5 blade would help me out. What's ur guys opinions on it? Thanks in advance!
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Old 07-21-2011, 10:25 AM
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Maybe your X dimension is too high?
And without really knowing the engine, there is no guarentee of HP.
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Old 07-21-2011, 10:28 AM
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Sorry to say...your prolly 100 hp off in your guess. Most people think they have more than they actually do.
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Old 07-21-2011, 10:28 AM
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what were you doing before?? prop/rpms/speed before engine rebuild.

my 454 mag 385hp can push a 21p M+ or 21 rev 4 to the rev limit..

Have you tried a 23 rev 4?
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Old 07-21-2011, 10:34 AM
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Originally Posted by Stormrider View Post
Maybe your X dimension is too high?
And without really knowing the engine, there is no guarentee of HP.
I am running a 14 1/2 x dimen. I bought the boat from Rogers performance marine. Here in Utah and the are known atleast locally for being the only reliable performance boat dealership around. They built the engine it has 90hrs on it. The specs I do kno are 502 punched to 509, eagle rotating assembly JE pistons. aluminum heads with ferrea valves titanium springs and retainers with dart rocker guard. Also it has all the bolt ons.... Imco water injected manifolds. Full msd Ignition The cam I have no idea of. It's running a holley 4 dble pump.

But u are right there is no way I can verify HP output. No engine dynos in Utah either.
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Old 07-21-2011, 10:37 AM
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Quote:
Originally Posted by nailit View Post
what were you doing before?? prop/rpms/speed before engine rebuild.

my 454 mag 385hp can push a 21p M+ or 21 rev 4 to the rev limit..

Have you tried a 23 rev 4?
Engine was built before I bought the boat. No the only rev 4 I have tried is the 21p. I am wondering if the outdrive was re geared??
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Old 07-21-2011, 10:39 AM
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Quote:
Originally Posted by tinman565 View Post
Sorry to say...your prolly 100 hp off in your guess. Most people think they have more than they actually do.
I am really hoping that's not the case. I got the 600 number from the Roger the owner of the company/ engine builder
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Old 07-21-2011, 10:55 AM
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Prop issue.
I had my 26' boat with 454 Merc. mag. Bravo 1, mirage 23" prop. clocked at 69.3
You should do low/mid 70's with a 502 and try 24-26 props.
502's have enough torque and a 24' boat is light enough.
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Old 07-21-2011, 11:02 AM
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Prop issue.
I had my 26' boat with 454 Merc. mag. Bravo 1, mirage 23" prop. clocked at 69.3
You should do low/mid 70's with a 502 and try 24-26 props.
502's have enough torque and a 24' boat is light enough.
I have a Quicksilver 3 blade 25p i used and on take off it blows out so bad it bounces the rev limiter. once i plane out i get same mph but only 4800 rpm. Here is a pic of the engine.



http://s1186.photobucket.com/albums/...1.jpg&newest=1

Last edited by 348Travis; 07-21-2011 at 11:05 AM.
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Old 07-21-2011, 11:18 AM
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I hate to say it but the fact that you're only turning a 21P prop to 5100 tells me you're down on power.

Personally I would try a 23P Rev4 and see what happens. But I'm guessing similar speeds at lower rpms.

Are you getting full timing advance? Jetted correctly for your altitude?
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