21ft Sleekcraft diplomat DT tunnel hull help
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21ft Sleekcraft diplomat DT tunnel hull help

  1. #1
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    Default 21ft Sleekcraft diplomat DT tunnel hull help

    Hi just bought a 21ft Sleekcraft Diplomat DT tunnel hull open bow. Its a v bottom with two tunnels. It's a 1989. Has a 502 bbc with a Berkeley JG w/ hyd place diverter. Won't have a chance to run her for a few weeks and she is going to stay in Parker AZ.just curious if anyone is familiar with these boats and can steer me in the right direction as far as a good pump set up befor I tow her out there. Contemplating a droop snoot and ride plate setup and/or moving the pump back. As far as what I am after as a end result mid 60's to 70 mph with a smoth ride . The bbc 502 seems to be a stocker gen 5 with a 850 dp Holley , msd ignition and Imco power flow exhaust . I'm guessing cam and port job could get me into the mid to high 500hp range, ANY helpful advice from anyone with this boat or something similar is much appreciated. Not trying to be Ricky racer just trying to figure out what it will take to get the heavier tunnel to pack some air and move.

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    Senior Member namba860's Avatar
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    Nice boat i had one with a 260 mercruiser package low 60 mph out of the box.

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    Senior Member hihosilver's Avatar
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    I have 20' sst and it did 70 (gps) with 320 hp bbc

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    Senior Member jetboatperformance's Avatar
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    Welcome to the boards , lets see some pics Tom

  7. #5
    Haulnass
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    You beat me up to Heritage by 1 day !!! I hope you enjoy the boat open bow jet and tunnel is rare setup. keep us posted on results
    of the testing and if you need to sell it before i find another ? . enjoy Bill.

  8. #6
    Senior Member hihosilver's Avatar
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    I saw a pic of a open bow but didnt know if they all were, I wish mine was

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    Yeah haulnass I drove 600 miles round trip as soon as I could, been looking for something decent and always got beat out . Called out sick and made the drive. My girlfriend seems on board ( half the battle ) and so super happy with the purchase so far. Needs some love but all in all a good boat. Maybe Elsinore lake this weekend for some base line testing. Get a good idea where I am now and go from there. Hihosilver what pump setup are you running on the 20ft sst ?

  10. #8
    Haulnass
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    Quote Originally Posted by Jetskijim View Post
    Yeah haulnass I drove 600 miles round trip as soon as I could, been looking for something decent and always got beat out . Called out sick and made the drive. My girlfriend seems on board ( half the battle ) and so super happy with the purchase so far. Needs some love but all in all a good boat. Maybe Elsinore lake this weekend for some base line testing. Get a good idea where I am now and go from there. Hihosilver what pump setup are you running on the 20ft sst ?
    I did the same thing today since i worked when you were buying on Monday.. since my wife didn't want the pioneer going to Havasu !
    Picked up 21 commander open bow for our vacation today.There's a open bow Baker in Tucson... 1988 Baker Open Bow Tunnel Jet Boat
    A little bit of a hike for me .

  11. #9
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    Lot of pink but man that's got a lot of the right parts. I see he is running a droop snoot on that . I missed a beautiful red baker tunnel open bow here in Tustin ca . Great looking boats ( Orange county) old guy had it, show room clean ... Sold in 2 hours . Good luck on looking. If you get somthing similar maybe I can give some advice on what's working for me .... Trying a strait snoot and droop snoot on sat. See if it helps.

  12. #10
    Senior Member hihosilver's Avatar
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    similar to the baker, motor is 489 all roller but haven't put the alum heads on as 200 hp only got me 1 mph faster, need to work on bottom and pump
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  13. #11
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    best advice i have for you is sell that tank and go find the lightest 18ft cp you can
    haha about time you got a ride cant wait to see you at the river

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    Hmmm... did some testing today for a base line At the worlds best lake, the where the sparkling emerald green water is only second to the sweet odor of yesterdays sushi, Lake Elsinore , SO.. Looking like a pump rebuild (bearing noise & cavitation) ... looking to pick up some more speed, turning the alumimum A impeller at 5300 RPM, seems like cavitation occurs and the boat takes a lot of RPM to get on plane.... looking for 10-15 MPH more. :/ .

  15. #13
    Senior Member hihosilver's Avatar
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    I went from 320 hp to 550 appox. and 4700 to 5100 rpm with alum A impeller and went from 70 to 71 mph on gps, I am thinking ss A-B cut to get to my cams 5700 power point but it needs ride plate , shoe and intake redone

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    Yeah actually got the pump apart, turns out the impeller was shot. Had it measured it's between an AB and a B. Talked it over with my buddy and the pump guy, think we are going to start with an aluminum A and work from there. Gotta tighten that pump up

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