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Originally Posted by hec2buck
(Post 3955287)
Hello Blue Thunder,
I take it you had your motor dyno tested and it made 625 hp at 6000 rpm w/5 psi boost? I ask this because most 500 hp motors that are super charged, make 600-700 hp at 5 psi and 52-5400 rpm. No labbing will increase prop rpm 1000. You will have to drop down in pitch to get the 6000 you require. However, I would agree that a pulley change is in order, as long as your cam profile does not require 6000 rpm. If this is a stock 502 cid, 500HP then the cam will not tolerate 6000 rpm. You will want to stay at 5400 rpm and change pulleys. As was mentioned earlier, you not making as much power now as you were with your prior set up. Please call to review this in more detail. Thanks, Thom |
On my 509 with a 741 cam and mild ported heads I only got 2-3 psi with a 5 psi b&m 250 setup no matter what rpm I pulled to. 5800 netted the same psi or less. I switched to a mega blower and super choler and I have 6.5 anytime I go WOT above 4200 rpms.
With 625 hp you should be able to spin a 26-28 pitch to 6000 rpms. I was able to spin a 30p bravo 1 to 5600 pretty easily. Maybe the different hulls come into play but I would think a fountain would be similar to my velocity. |
Originally Posted by 12meter joe
(Post 3954641)
Not sure if its the same but on my car changing to a smaller super charger pulley would produce more boost and hp but changing the crank pulley would produce more tq and hp with less heat. Not sure if this applies to boats being a whole different world?
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Well my Dyno sheet says 2 lbs at 3800 rpm. If I'm reading this rite. I'm gonna check for belt slip at kinks or leaks in my hose. Also sorry cp5899 for not getting back to you on the prop. I borrowed one a 30p and it didn't work anyway
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Not a problem. I'm in no hurry to sell it as its a spare for me in case I need it. I would think with that kind of power you should be running a 30p though.
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Yeah thought a 30 p was going to be the rite prop but I guess not. It put me down at 4800 rpm. That's too much lug on the motor for me
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What RPM does your 26p Bravo net? You should baseline off that prop and go from there.
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Originally Posted by 98Fever27
(Post 3954096)
I was running a 26p 4 blade bravo prop on my stock hp 500 carb. I put a B&M 250 blower on it and I am now pushing 625 hp. I am running a 30 p 4 blade bravo now. My only problem is I need another 1000 rpm so I can get my boost up to 5 psi then I think the 30 p will be the rite prop for speed. I am wondering if I can get it labbed by bblades and get the rpms back. I was running 5200 stock. Now I am at 4900 and should be pushing 6000. Any thoughts?
Unless you changed the ignition, then the stock rev limiter will kick in at 5350rpms. A 250 bolted onto a stock HP500 should make 625hp easily when set up correctly. Was the blower refreshed ever??? It sounds like it is not making boost correctly, assuming you have the correct pulley combo to make 5# of boost on a 502 engine. |
Pm me your phone number as I am only 15 miles from you and I may be able to help you with your questions and might have props I could let you try to see where you need to be, sounds like you need to get motor sorted out before worrying about propping from what you are saying, but either way get with me and I will try to help, a customer who has a 27 fountain that he just bought (Dean) was telling about you last week when I fixed his outdrive, Smitty
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I met 98 fever 27 today after talking to him on phone earlier this week. He found 2 smaller pulleys to try to make more boost and I borrowed him a labbed 28 CE and merc/bblades labbed 30 to run along with his hopefully higher boost! I LOVE seeing a guy go faster and after this test he should know what prop his boat really needs and can have BBlades or CE lab his own 30 or build him the right prop, Smitty
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