Impeller Size question.
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Impeller Size question.

  1. #1
    Senior Member nosfomoco's Avatar
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    Default Impeller Size question.

    Ok I bought a bigger boat than I am used to, a 1978 Eliminator Sport Cruiser 20.5 ft. I love the boat so far. It drives better than any of my previous jets ( 21 commander & 18 Kachina), also seems to get on plane quick for its size and lack of power. It is stock as far as i can tell and the Old 460 is warn out which shows with its top speed of 52mph at 4200 rpms. The plan is to install a motor that I previously ran in my 18 foot kachina( .080 460 Ford 11.1 comp, Comp 300AR solid roller cam) in the Eliminator. That motor turned an Aggressor B cut impeller to 5900 [email protected] 93 mph, It was topped with a Weiand Tunnel ram W/2 750 DP holleys. I am no longer going to run the tunnel ram, I want to keep everything under the cover so i think it will be topped with either a Trick flow intake or the FMS with a 1050 Dominator. I bought Lightening headers also to keep under the cover, but I am not sure where to start with the impeller. Not sure how heavy these boats are. I was thinking that the Same B cut aggressor might be ok? Want to keep the rpm up, but dont wat to loose to much holeshot. I am also adding a rideplate and shoe, not suer which droop works good on these because it seems to ride pretty dry with just the factory Jet o vator. Any guys with this hull please send any advise my way, Thanks.
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    1978 Eliminator Sport Cruiser 20.5ft BBF 460!

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  3. #2
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    Default impeller

    Figure out what is in the boat now and try it with the new engine. Since you are changing some other things you might want to wait and see how the current impeller works. I would think that you probably need an "A" or "AB" impeller to give you the better hole shot in that boat, you will loose some RPM's but the hole shot will be much better with the "A" versus a "B" cut impeller. IMO

    Chris

  4. #3
    Senior Member jetboatperformance's Avatar
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    Default

    Quote Originally Posted by nosfomoco View Post
    Ok I bought a bigger boat than I am used to, a 1978 Eliminator Sport Cruiser 20.5 ft. I love the boat so far. It drives better than any of my previous jets ( 21 commander & 18 Kachina), also seems to get on plane quick for its size and lack of power. It is stock as far as i can tell and the Old 460 is warn out which shows with its top speed of 52mph at 4200 rpms. The plan is to install a motor that I previously ran in my 18 foot kachina( .080 460 Ford 11.1 comp, Comp 300AR solid roller cam) in the Eliminator. That motor turned an Aggressor B cut impeller to 5900 [email protected] 93 mph, It was topped with a Weiand Tunnel ram W/2 750 DP holleys. I am no longer going to run the tunnel ram, I want to keep everything under the cover so i think it will be topped with either a Trick flow intake or the FMS with a 1050 Dominator. I bought Lightening headers also to keep under the cover, but I am not sure where to start with the impeller. Not sure how heavy these boats are. I was thinking that the Same B cut aggressor might be ok? Want to keep the rpm up, but dont wat to loose to much holeshot. I am also adding a rideplate and shoe, not suer which droop works good on these because it seems to ride pretty dry with just the factory Jet o vator. Any guys with this hull please send any advise my way, Thanks.
    The Aggressor "B" will likley be a good starting point to try as they tend to act more like an A Berk , the ride plate and shoe will be good additions to provide some adjustability, wouldn't consider a droop personally didn't immediatley find specs on your Comp 300 but if it was in your Kachina I suspect it was O'transom headers and you may want to check specs ([email protected]) for compatibility with your Lightnings thru hulls . I've owned two of these Boats , a Vdrive and a Jet and they are on the heavy side . The 5900 rpm figure suggests your motor was making around 600 hp, should do nicley in the cruiser Tom

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    Cole SS cole ss's Avatar
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    Default

    Do you have a loader on you boat? When I put one on my Cole I gained 5 mph, 49 to 54+. My boat has a delta pad and likes a loader that has a lot of bite, hangs down 5/8. My boat is also 20.5. 454 stock, max speed 58 @ 4400. Works great with an A impeller. Ready to install rebuilt 454 with 450hp. Built motor to match impeller. Figure out where your motor makes best hp amd match to impeller.

  7. #5
    Senior Member nosfomoco's Avatar
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    Default

    Thanks for the info. I do plan on running a Open center pro loader grate. here are the cam specs( I didnt think there was much chance of reversion with jacketed headers?):

    Specifications Intake Exhaust
    RPM Range: 3200-7200 Valve Lash: .020 .020
    Valve Timing: 0.015 Duration: 300 300
    Lobe Separation :110 Duration @ .050" Lift: 262 262
    Intake Centerline:106 Valve Lift: 0.663 0.663
    Lobe Lift: 0.383 0.383
    Valve Timing @ 0.015 Lift:
    Exhaust
    Closes 36
    ATDC
    Opens 84
    BBDC
    106
    Intake
    44 Opens
    BTDC
    76 Closes
    ABDC


    Mechanical Roller-Ultimate pro street cam 4000+ stall/4 speed,11:1 comp, radical idle.
    1978 Eliminator Sport Cruiser 20.5ft BBF 460!

  8. #6
    Senior Member jetboatperformance's Avatar
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    Default

    Quote Originally Posted by nosfomoco View Post
    Thanks for the info. I do plan on running a Open center pro loader grate. here are the cam specs( I didnt think there was much chance of reversion with jacketed headers?):

    Specifications Intake Exhaust
    RPM Range: 3200-7200 Valve Lash: .020 .020
    Valve Timing: 0.015 Duration: 300 300
    Lobe Separation :110 Duration @ .050" Lift: 262 262
    Intake Centerline:106 Valve Lift: 0.663 0.663
    Lobe Lift: 0.383 0.383
    Valve Timing @ 0.015 Lift:
    Exhaust
    Closes 36
    ATDC
    Opens 84
    BBDC
    106
    Intake
    44 Opens
    BTDC
    76 Closes
    ABDC


    Mechanical Roller-Ultimate pro street cam 4000+ stall/4 speed,11:1 comp, radical idle.
    Jan (Lightning) has alot of cam/header/build data and information and is always willing to help , typically the magic number for potential reversion issues with thru hulls is 235 to 240 ([email protected]*) call if we can help as well Tom

  9. #7
    Senior Member Brendellajet's Avatar
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    Default

    Big factor with reversion is exhaust tip location. Tips under water, partially under or not at all?
    "He is a lover, not a fighter. But he's also a fighter, so dont get any ideas."

  10. #8
    Senior Member nosfomoco's Avatar
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    So I am assuming I will still make almost the same power as I had with the tunnel ram going with a single dom 1050, so what will 600hp do in that Hull. the bottom is real straight. I had high hopes of the 75mph range. Got a feeling I need to bring on the Spray.
    1978 Eliminator Sport Cruiser 20.5ft BBF 460!

  11. #9
    Senior Member jetboatperformance's Avatar
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    Default

    Quote Originally Posted by nosfomoco View Post
    So I am assuming I will still make almost the same power as I had with the tunnel ram going with a single dom 1050, so what will 600hp do in that Hull. the bottom is real straight. I had high hopes of the 75mph range. Got a feeling I need to bring on the Spray.
    Thats probably a realistic goal and number with an honest 600 hp

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