Quest for 5500 RPM's....
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Quest for 5500 RPM's....

  1. #1
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    Default Quest for 5500 RPM's....

    I am in need of some helpful advice! Owner of a 21ft day cruiser and currently on my second rebuild. I am on a quest for higher rpm's, approximately 1000 more. Boat seems to reach around 4500 max rpm's, but what now?

    Engine set up:
    BBF 460
    Sleeved, Bored .30 over
    Stock crank and rods
    Edelbrock carb 750 cfm
    Edelbrock Performer RPM Aluminum Heads 75cc
    Edelbrock Performer Aluminum intake manifold
    Trick Flow Roller Rockers
    Comp Roller Cam, Roller Lifters, Pushrods

    Jet:
    Berkley 12JC, Aluminum A impellar
    Hydraulic Place Diverter
    Stock loader

    I know the added length and weight being a day cruiser limits my power. Should i concentrate on my jet? Add a snoot,shoe, different impeller??? I really would like to surpass 5000rpms. Any suggestions would be appreciated.

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    Senior Member Futs's Avatar
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    Whats the compression and cam specs?

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    Senior Member lbhsbz's Avatar
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    4500 RPMS with an "A" impeller is about 330hp.

    5500 RPMS with an "A" impeller is about 600 hp


    Not sure what you're running for a cam, but most solid rollers will not make their peak torque at 4500 RPMS. Sounds like your package makes it's peak HP closer to 6000....most likely higher. What are the cam specs? I'd run all the specs on a desktop dyno just to get an idea of what the powerband looks like and where.

    The obvious solution is to cut the impeller down to a "B" and see what happens. You'll be making more power at the higher RPM...only problem is that big boats generally like bigger impellers (A or AA) for getting out of the hole. You may need to run a "B" with an inducer....or find a way to bring the powerband on your engine back down to a RPM range that you can use with your pump.
    Last edited by lbhsbz; 07-13-2010 at 12:07 AM.

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    Senior Member Futs's Avatar
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    Quote Originally Posted by 460junkie View Post

    I know the added length and weight being a day cruiser limits my power. Should i concentrate on my jet? Add a snoot,shoe, different impeller??? I really would like to surpass 5000rpms. Any suggestions would be appreciated.
    The weight or lenght dont come into play when your talking HP/torgue or rpms. If you make the power, it will spin that rpm. Usually a loose pump will spin more RPM than a nice new tight pump. Sounds like you need more power to get into the rpm range your looking for. But why are you looking to spin that kind of rpm? If the engine wont make the power up there your just going to kill the engine. Granted, it will sound bitchen, but you will actually go slower spinning more rpm then actually having the power to do so.

  7. #5
    JRPM/e-PerformanceMarine Squirtin Thunder's Avatar
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    If you ditch the 750 carb you have and go with a Holley 850 you could pick up 100 - 300rpms. You may think about going to a 3A impeller or even bigger and used the torque of the BBF instead of HP. How fast is the boat running now ?
    Last edited by Squirtin Thunder; 07-13-2010 at 12:28 AM.
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  8. #6
    Senior Member lbhsbz's Avatar
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    Quote Originally Posted by Squirtin Thunder View Post
    If you ditch the 750 carb you have and go with a Holley 850 you could pick up 100 - 300rpms. You may think about going to a 3A impeller or even bigger and used the torque of the BBF instead of HP. How fast is the boat running now ?
    He's got a 460 roller motor and you think an 850 carb will do a damn thing for him when he's turning it 4500 RPMS? A 2 barrel would probably run as good or better than his current carb because he's nowhere near the top of the powerband.

    3A Impeller?....let's pull it even further out of the powerband...better get a smaller 2 barrel.

    To the OP, your engine is making 330hp at 4500rpms. This is a fact.

    Your engine, with your upgrades, makes considerably more peak hp than 330....you just have to determine where it makes that horsepower, and set up your pump accordingly to let the motor spin and use that horsepower. The downside is that going to a smaller impeller which will let the motor spin will also result in decreased performance out of the hole. An inducer can help with this.

    In your case, it may be better to simply change your engine configuration to bring your peak HP and TQ down to a lower RPM range. This will still allow you to pull big impeller to get the boat on plane quickly.

    like everything, it's a balancing act.

    You must understand...jet daycruisers are not gonna run 80+ without serious HP.

    Like Futs said....your engine/pump don't even know they're in a boat. you could tie it to the dock and it would still turn 4500 rpms in it's current form.

    .
    Last edited by lbhsbz; 07-13-2010 at 01:15 AM.

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    Quote Originally Posted by Futs View Post
    Whats the compression and cam specs?
    Compression with the 75cc heads run 10:0:1 .. Cam specs are on Comp Cams website. Its the Ford 460 Roller Marine cam. RPM range on website says 5500-7500, any suggestions on another set up?

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    Senior Member propless's Avatar
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    Only cam I see there with that RPM range is a solid roller grind # 319CR-10.

    Description = Mechanical Roller-Baseline for unblown gas or alcohol. Two 4 BBL.s or injection.
    http://www.compcams.com/Cam_Specs/Ca...csid=1030&sb=1

    Looks like its just a little bit big for that motor.

  11. #9
    JRPM/e-PerformanceMarine Squirtin Thunder's Avatar
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    Quote Originally Posted by lbhsbz View Post
    He's got a 460 roller motor and you think an 850 carb will do a damn thing for him when he's turning it 4500 RPMS? A 2 barrel would probably run as good or better than his current carb because he's nowhere near the top of the powerband.

    3A Impeller?....let's pull it even further out of the powerband...better get a smaller 2 barrel.

    To the OP, your engine is making 330hp at 4500rpms. This is a fact.

    Your engine, with your upgrades, makes considerably more peak hp than 330....you just have to determine where it makes that horsepower, and set up your pump accordingly to let the motor spin and use that horsepower. The downside is that going to a smaller impeller which will let the motor spin will also result in decreased performance out of the hole. An inducer can help with this.

    In your case, it may be better to simply change your engine configuration to bring your peak HP and TQ down to a lower RPM range. This will still allow you to pull big impeller to get the boat on plane quickly.

    like everything, it's a balancing act.

    You must understand...jet daycruisers are not gonna run 80+ without serious HP.

    Like Futs said....your engine/pump don't even know they're in a boat. you could tie it to the dock and it would still turn 4500 rpms in it's current form.

    .
    It is a BBF if it can't pull a A with the HP to 4600pms he needs to use the torque. My very mild .030 466 is pulling a 9.5" with .018 thrust to 4400rpms with a 750 Carter, I put a 800 dp on it and gained 100 rpms. So I am betting a 850 will get me 4600rpms. If I can do that with a 9.5" impeller he should be able to do it with a A. Jet boats love carberation and it has been proven many times. Just because it is a roller motor does not mean it will make 800hp at 5800rpm. He has a big boat it need a big impeller. I bet by going to a A3 and a 850 he will turn the same or more RPM and go faster and have much better everything. But what do I know this is only what I do for a living.

    Just looked at the cam specs what were you thinking, that is not a race boat, skip what I said and put a C impeller in it turn 5800 rpm and run maybe 40mph.

    Like Futs said....your engine/pump don't even know they're in a boat. you could tie it to the dock and it would still turn 4500 rpms in it's current form.
    With a tight pump it will not work ! Good luck ! I know mine would rip the dock loose !
    Last edited by Squirtin Thunder; 07-13-2010 at 04:07 AM.
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  12. #10
    cj812 ralph brunt's Avatar
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    Quote Originally Posted by propless View Post
    Only cam I see there with that RPM range is a solid roller grind # 319CR-10.

    Description = Mechanical Roller-Baseline for unblown gas or alcohol. Two 4 BBL.s or injection.
    http://www.compcams.com/Cam_Specs/Ca...csid=1030&sb=1

    Looks like its just a little bit big for that motor.
    call straub and get a cam made, you are never getting there with this cam

  13. #11
    Senior Member 787chuck's Avatar
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    get a hold of paul lakes only on here he can help you sounds like your motor set up is off when i ran a ford my set up was a lot more mild then what your running and we pulled a lot more rpms then 4500 and we used the TQ of the ford and keep the impeller big to move our tank of a boat and the thing moved out and ran for a long time

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    Senior Member lbhsbz's Avatar
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    With a tight pump it will not work ! Good luck ! I know mine would rip the dock loose !
    LOL...did you try that already once?

  15. #13
    JRPM/e-PerformanceMarine Squirtin Thunder's Avatar
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    Quote Originally Posted by lbhsbz View Post
    LOL...did you try that already once?
    Actually I was helping a friend set a dock a few weeks ago here on the river very intresting work for a jet boat.

    Quote Originally Posted by 787chuck View Post
    get a hold of paul lakes only on here he can help you sounds like your motor set up is off when i ran a ford my set up was a lot more mild then what your running and we pulled a lot more rpms then 4500 and we used the TQ of the ford and keep the impeller big to move our tank of a boat and the thing moved out and ran for a long time
    I agree 100% a bone stock BBF 460 make 420ftlbs of torque. The cam I got from Ralph Brunt would be perfect for your aplication, tons of low rpm power and great midrange. Ralph can you post up those #s. It would spin my MPD A to 5400rpm with .018 thrust clearance, .040 radial clearance and .018 trailing (impeller to stuffer).
    Last edited by Squirtin Thunder; 07-13-2010 at 09:06 AM.
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    Resident Ford Nut Sleeper CP's Avatar
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    Quote Originally Posted by 460junkie View Post
    Compression with the 75cc heads run 10:0:1 .. Cam specs are on Comp Cams website. Its the Ford 460 Roller Marine cam. RPM range on website says 5500-7500, any suggestions on another set up?

    Comp lists quite a few mech roller cams in their reg catalog I sure the hell hope you don't have the can someone else listed from the on-line catalog. I know they have a cam that states " ski-jet with A Impeller". Actually I doubt you could get that cam ( blown alky) to work with P/V unless you had huge valve reliefs.

    First post the cam you have so they are not guessing at it. It will make all the difference.

    Better info ......better answers.

    S CP
    Last edited by Sleeper CP; 07-13-2010 at 09:49 AM.

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