Engine Location in Hull...?
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Engine Location in Hull...?

  1. #1
    Super Moderator HammerDown's Avatar
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    Question Engine Location in Hull...?

    Not related to my other thread...(engine tilt)
    Years ago when I set my Pump back some 6" I gained some nice real estate in the boat with the rear bench also going further back.
    HOWEVER I feel with the weight of the BBC now further back, unless I'm really into the throttle the rear of the hull is heavy/digging in too much, such as with cruising speeds.
    Soooo I'm thinking of adding a Jet-A-Way this off season that would move the engine forward some 6"...sound about right?
    A little less room in the boat again but I feel the whole riding attitude of the Hull at cruising speeds and top end will be happier again...no?

    Below is a pic where the inside of my transom and engine is located...some 21" between the rear of the engine and transom. I think it's too far back for my 21' Daytona.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Senior Member bp298's Avatar
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    is that a 3 point bellhousing? 6" should be plenty, but the 3point system won't work with the jetaway...

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    Senior Member H20MOFO's Avatar
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    I'm all ears on this one. Hammer did you lose or gain performance with the setback? Or did you change too many things to really know? Mine is set back also,and I wonder if the boat would pack air better running flatter??
    Another Hot Boat refugee

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    I read somewhere ( ? ) that race boat builders are putting the engines more in the center of the boats (vs. more towards the stern) than they use to, I have no idea why.

    I counted 8 colors on that bitchin paint/gel coat job. I'll go back to lurking now.

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    jetboataholic HawaiianJet's Avatar
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    Quote Originally Posted by bp298 View Post
    is that a 3 point bellhousing? 6" should be plenty, but the 3point system won't work with the jetaway...
    I think he said in his other thread that he is ditching the 3-point mount and installing a 4-point mount.
    HJ

    ***FOR SALE*** 1978 19' Full Stringer Hawaiian Molokai Jet Boat w/ Berkeley 12JC-AB and Chevy 440 Tall Deck ***FOR SALE***

    Quote Originally Posted by mako shark mark View Post
    Oh yeah, Forgot to mention that the hull is a special mixture of speedcote, herculiner and rain-x, all blended together- good for another 8 mph top end.

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    Senior Member GT Jets's Avatar
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    I would have no problem saying the engine should go forward, especially in a tunnel. When the pump was set back I believe you took a huge step forward and a small step back, the pump will stay loaded better, but the hull wants to "stand up" causing you to loose some of the tunnel effect. I also think that by moving the engine forward the ride quality will improve due to the fact that there will be more air pressure under the engine area which should offset bow hop...Four point mounts are a must IMO.

    Sweet ride!

    GT
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by H20MOFO View Post
    I'm all ears on this one. Hammer did you lose or gain performance with the setback? Or did you change too many things to really know? Mine is set back also,and I wonder if the boat would pack air better running flatter??
    As GT Jets mentioned I did move forward in performance however I may have hurt myself just a little at cruising speed and where I spend 95% of my boating time. After the pump setback the boat ran the same RPM/MPH at cruising speed however the rear of the boat seems a 'tad' heaver in the water. Also I had to relocate my boat forward on the trailer a few inches to again distribute the weight properly.
    The Pump set back is a plus...the biting edge of the pump is further back thus allowing more of the hull to air out(if you have the speed) however, I feel the nose of the boat is up a bit more then I would like and I'm tabbing down more with the diverter to compensate and maybe bending the water more then necessary??? No biggie I'll just put the engine up a few inches with the addition of a Jet-A-Way.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by GT Jets View Post
    I would have no problem saying the engine should go forward, especially in a tunnel. When the pump was set back I believe you took a huge step forward and a small step back, the pump will stay loaded better, but the hull wants to "stand up" causing you to loose some of the tunnel effect. I also think that by moving the engine forward the ride quality will improve due to the fact that there will be more air pressure under the engine area which should offset bow hop...Four point mounts are a must IMO.

    Sweet ride!

    GT
    Good feedback above GT and I agree however...I'm not fighting any "bow hop". If anything I have what I call a ever so slight bit of bow isolation at the very front of the boat. Almost like a very slight left/right bow hunt...nothing scary or crazy and it's not all the time. Could be wind/water conditions???
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Wet
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    Quote Originally Posted by canuck 1 View Post
    For top speed I would leave it where it is

    Like Hammer said, 95% of the time is cruising.
    0.01% is top speed, but has Hammer ever really aired that thing out? Seriously? On another note, how much does the increased rearward distributed weight increase blowover potential?
    And lastly, were pump/motor combos thrown in hulls to what "fit" better? We didn't have the data available back then to optimize placement as we do now.

  12. #10
    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by Wet Dream View Post
    Like Hammer said, 95% of the time is cruising.
    0.01% is top speed, but has Hammer ever really aired that thing out? Seriously? On another note, how much does the increased rearward distributed weight increase blowover potential?
    And lastly, were pump/motor combos thrown in hulls to what "fit" better? We didn't have the data available back then to optimize placement as we do now.
    "Have I really aired that thing out"...absoutly, more so on the Delaware River vs Anna >too many boats and Islands around
    Look here at 0:12 I kick it in the c*nt!
    When looking at that short video you can see the water breaking at the drivers seat (crusing) and then further back as the hull "aires out".

    My Boat has always had loooong legs meaning, it takes some time to get up to mph...I feel it's because I'm low on HP for the Impeller size and weight/size of the hull.

    As in your last two comments, I too would like to know (if) back in 1983 when my boat was built and (if) the pump was already 'set-back' would the engine location be taken into consideration (or) would it just go where it would have ended up...which would have been back where it is now.
    I'm sure Greg Shoemaker could answer this.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

  13. #11
    Senior Member wizard612's Avatar
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    By moving the motor forward you will do many things but most importantly you will move the CG forward and make it that much more difficult to blow your tunnel over. Best attitude is high and flat...

  14. #12
    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by canuck 1 View Post
    by the good builders it was
    So would you be saying when my 1983 Daytona was built by (Eliminator) they did NOT set the pump back because it would put the engine in the wrong place?
    And/or if Eliminator set the pump back would they have used a longer solid drive shaft to keep the engine more forward for proper hull/weight distribution?
    I'm really curious about this.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Wet
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    Quote Originally Posted by canuck 1 View Post
    I don't agree with that. We were working on that with the builder in 1977/78 ....set back pump and all in the glass hulls.
    Now our stuff is half the weight with a bigger % on the ass

    Really? What Cad/cam program were you using in 77? I'm not believing for one second that hulls built in the 70's could be designed, built, tested and optimized as todays counterpart given the same materials. Data aquisition speaks volumes.

  16. #14
    BTC cardcarrying member SuperSoaker's Avatar
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    Quote Originally Posted by Wet Dream View Post
    Like Hammer said, 95% of the time is cruising.
    0.01% is top speed.

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