22.5 foot spectra splash......need more speed!
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22.5 foot spectra splash......need more speed!

  1. #1
    Ralphs club member LSXINDUSTRIES's Avatar
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    Default 22.5 foot spectra splash......need more speed!

    Hey guys, i have a '75 "california fiberworks" jet boat, basically looks like a spectra mini day cruiser. Almost 23' long, closed bow, no windows, seats 6 comfortably. Never weighed it, but im sure its kinda heavy for its size. Boat has a Hardin marine 460 with a berkely pump spinning a "A" impeller. Engine will spin about 4400-4500rpm WOT, pushing the boat to 48-49 mph on the GPS, with 2 people on board. Does this sound about right for a boat this size with this combo? The 460 has thru transom wet exhaust, only mods are a performer intake and a 750cfm holley vac secondary carb. I would like to get this boat up in the high 50 - low 60mph range, keeping my A impeller. Suggestions? I was also thinking about repowering the boat with a LQ4 or LQ9 6.0 Gen III LSX motor, but with a carb. They make a easy 450 flywheel horsepower by 5000 rpm with a 850 holley, small cam around 210-214 @ .050 and a single plane carb intake....and ive got 7 of them lying around at the moment And it would be stone cold reliable at that HP level, probably better on gas also. I would build the 460.....but i think trying to get anything over 450 horsepower with that motor will require aftermarket heads and some considerable $$$. I could be wrong though, im not a ford guy and it just seems that every post i read from ford forums wind up with HP in the high 300's around 4500rpm, using factory available heads. I dont want to run a solid cam, or even a large cam for that matter, hence my consideration of the LS engine. opinions, Input?
    Last edited by LSXINDUSTRIES; 12-28-2009 at 05:34 PM.

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    Senior Member DuaneHTP's Avatar
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    We just put a 514 ford built specifically built for a jet boat in a boat like that, and we got 61 mph out of it with a AA Hi-Helix impeller. Man, what a cruiser. And that was at 4600 rpm. The guy loved it.
    I believe the motor made right at 500 HP, maybe a little more?
    Duane HTP

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    Senior Member WMorton's Avatar
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    What is the torque of the 6.0 with that configuration?

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    How straight is the hull bottom ? You can keep throwing horsepower ($$$) at it or just make "it all work together" ! I have a thought that it has 'hull bottom problems' and correcting them alone will get you up into the speeds you require. "Brains over $$$"

  7. #5
    Ralphs club member LSXINDUSTRIES's Avatar
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    You are probably right. I dont have much boat experience when it comes to hull design or troubleshooting hull designs for that matter. How can I tell if the shape of the hull bottom is really hurting performance? Is there any telltale traits to look for, other than the obvious (hull damage)?

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    Boat Nut sleekcrafter's Avatar
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    This posted many years ago, and many forums back.

    Hull Blueprinting 101 by Jeff Bennett-
    Hull blueprinting means different things for different hull designs. I will limit this discussion to vee bottom jet boat hull blueprinting. It is assumed that the reader has a working knowledge of body work and fiberglass repair. It is best to talk with or get assistance from someone who understands this skill. Also, there are many ways to blueprint a hull, this is the way I go about it.



    Basically, vee bottom hull blueprinting means to return the bottom of the hull to the shape that the manufacture originally intended. Over time, hulls can change shape or warp due to improper trailer fit, or hulls being removed from the mold too early. This warping often results in a 'hook", which is when the bottom of the boat at the transom is lower than the adjacent hull forward. This hook resembles a trim tab or cavitation plate in the down position. The result of this hook is to generate more lift at the rear of the boat, which forces the nose of the boat downward. The faster the hull speed, the more this occurs. Because of this tendency to push the nose down, the boat is prevented from getting loose (free from the water) and top speed is reduced. Usually the prime motivation of hull blueprinting is to increase top end speed. There are many steps to hull blueprinting.


    First, the amount of hook must be measured to determine whether or not the effort is worthwhile. The easiest way to do this is to use a 5-foot straight edge and place it lengthwise from the transom forward. Examine the bottom at several locations; down the centerline, at each lifting strake and at least one location between each lifting strake. You should concentrate on the lower part of the hull, usually at least 2 or 3 lifting strakes outboard from the centerline. At every location measure the gap(s) between the straight edge and the hull. The gap(s) is the amount of hook. If the hook is any more than 1/16" then a hull blueprint may be worthwhile. If you decide to go ahead and blueprint the hull, there are a series of steps required to accomplish the task.
    1) The boat needs to be stripped (remove the motor, battery, fuel, steering wheel, possibly the upholstery and anything that will fall out or be in the way when the boat is turned upside down.
    2) Now it is time to turn the boat upside down. Used car tires with blankets over them work well for this. First lay out 6 to 8 tires on the ground behind the boat and with the help of 6 or 8 of your friends (more if the boat is over 20 feet) and slide the boat off the trailer and on to the tires. Next, line up 3 or 4 tires in a location that when the boat is lifted up on one side, they will be between the ground and the hull on the opposite side. Have every one except 1 person gradually lift up on one side of the boat and the other person make sure that the boat does not slide off the tires. When the boat is at 90 degrees and resting on its side have each person one by one go around to the opposite side and then gradually let the boat down. One person needs to move the now vacant tires to the other side to be a resting-place for the boat when it is upside down. As you are letting the boat down, make sure nothing drags on the ground and that the tires are completely supporting the boat. Should you have a hoist, there are many ways to aid in this process, but I am not going to go into those here.

    3) Using the straight edge, make a detailed contour map of the bottom by measuring and marking how deep the gap is at various locations. A grease pencil is a good choice for this map. The blueprint area should be 5' long and out to the 3rd strake outboard from the centerline (2nd if you have a 2 strake per side boat).
    4) The amount of the step will determine how the 'hook' should be filled in. Never, by the way grind out a hook; many manufactures have made this mistake and ruined otherwise good hulls. Anything less than a 1/16" gap should be filled with body filler. Any body filler will work as long as primer and or paint seal it. The best filler is 3m Premium grade filler, which is waterproof. Between 1/16" and 1/8" gap can be filled with either Duraglass or fiberglass mat and resin. Anything over 1/8" should be filled with fiberglass mat and resin.
    5) Next, you need to grind the areas that will be filled. Use a 40-grit disk on a body grinder. The gel coat does not have to be completely removed, but all the shinny spots need to be eliminated and the surface must be rough.
    6) If you need to fill any areas with fiberglass, use 3 oz. mat and resin and do them first. A single lay up of 3 oz. mat is roughly 1/16' thick when soaked with resin. If you are not going to add fiberglass, go on to Step 7. Use a roller and remove any air bubbles. Try not to work in the sun. You can use fiberglass cloth over the mat, but you really do not need to add any strength and in this case mat alone will work fine.
    7) Once the fiberglass is dried, grind it with the body grinder and prep the surface for the body filler by washing that portion of the hull with acetone on a rag.
    8) Fill next with the Duraglass filler. Mix up a small batch of Duraglass and spread it on the areas you wish to fill. Using a straightedge and standing on the side of the boat, quickly place the straightedge lengthwise (relative to the hull) and slowly pull the straightedge towards you as you scrape the excess material off the bottom. Start the filling from the centerline and work outboard. When the Duraglass dries, use the body grinder again and smooth out the high spots. Repeat this process over the blueprinting area. Apply another application(s) until the hull is within 1/16" of being true.
    9) Now do the final filling using the regular body filler. This procedure is basically the same as Step 8, but instead of using the body grinder, use a long board with 40-grit sandpaper, sanding lengthwise. It will take three or four applications before the hull is straight.
    9b) The hull to intake interface needs to be blended. Just make sure that there is no part of the intake hanging below the boat, no forward facing steps and that you fill and smooth any gaps between the intake and hull. The finished blend should be a gradual entry and the intake should look as though it is part of the hull.
    10) Once the boat is straight, again use the long board with a 100-grit sandpaper and detail out the bottom. Some areas, especially around the intake will require hand sanding without the long board.
    11) Use glazing putty to fill the pinholes. Again sand with the 100-grit sandpaper.
    12) Mask the blueprinted area off and prepare the surface for primer by cleaning the surface with a thinner or acetone. If you use acetone, be careful to not remove the glazing putty, which will be attacked by the acetone.
    13) Primer the blueprinted area using a polyester primer. Put on a thick coat because it will help fill any remaining pinholes and seal the body filler. Dust coat the primer with a black lacquer to be used for the wet sanding step.
    14) Wet sand the primer with 220-grit wet/dry sandpaper. Follow that with 400-grit wet/dry.
    15) Now you are ready for the finish coat. Since polyester primer has been used, you have a few options on type of paint or Gel coat. I usually use catalyzed acrylic enamel or a lacquer based graphite finish (AKA speed coat), which is available from Rex Marine or Eddie Marine. Gel coat is the strongest finish, but it requires the most work. As I mentioned at the beginning, it is assumed that you have a working knowledge of bodywork. If you do not feel comfortable with the final paint step, either find someone who can do it for you or use the graphite paint because it is almost impossible to screw up.
    16) Let the final finish dry thoroughly (24 hours) and be careful not to scratch it when you put the boat back on the trailer. Now you are ready for the lake.

    Good luck!

    There are some pics of the masters work on page 2 on the link

    http://www.performanceboats.com//sho...hull+blueprint
    Upper Midwest Power Boat Association
    DRAG BOAT RACING UMPBA #926


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    Default screw the hull, lets talk LSx

    Do you have exhaust figured out for the LS motors? The only source I know of is manifolds from new zealand, or custom headers that cost more than my boat is worth.
    I have been thinking about an LS swap for a long time, they are tough to beat power-wise with a cam swap and little else, not to mention a couple hundred pounds lighter than BBC, BBF, or 455 olds. When my olds lets go, an LS is going in.
    What sort of goodies are needed for a carb'd LS for 500 hp, 500 tq level? Which stock oil pan (aka affordable) would work in a jet application but still provide additional capacity?

  10. #8
    Boat Nut sleekcrafter's Avatar
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    Malibu boats has offered all the LS series motors over the years, so used or new are likely available.

    Upper Midwest Power Boat Association
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    yeah funny thing on the OEM manifolds on the wake boats. They wont sell them as replacement parts. At least last time I checked.
    Last edited by slim pickens; 12-30-2009 at 06:07 PM. Reason: typo

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    Ralphs club member LSXINDUSTRIES's Avatar
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    As far as the exhaust is concerned, you can get your hands on a set of 351 ford exhaust logs, and then cut the head flange off and have a LS aluminum flange welded in place. The exhaust port spacing is almost identical, just the flange pattern and angle is different. I couldn't bring myself to spend $1500 plus on exhaust logs. 500 Horsepower is easy, you can push that with a 6.0 and a stock set of 317 heads. A 224/224 or 224-228 TTR or comparable cam will produce the HP number @ the flexplate, but will most likely produce torque in the 430-450 range. It will want to rev 6300-6500 though. A 6.0 equipped with L92 heads and a 218-224 or comparable cam will make similar numbers, but power will be closer to the 6200 mark on a 113 LSA. 500 ft pounds of torque and 500HP at a lower RPM would require a 383 or 408 / 413 stroker, or a blower. Your're only working with 364 cubic inches, so low RPM big torque numbers can be a little difficult to achieve compared to a big 496. They can make a ton of horsepower with cam and heads, upwards of 600 natruraly aspirated fairly easy with the right heads on pump gas, but the RPM range will be 6500+

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    Ralphs club member LSXINDUSTRIES's Avatar
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    Oil pans from a CTSV cadillac, F body camaro or even the 04-06 GTO will likely work, they're not much deeper than a standard 454 or 460 truck pan. The GTO pan is a front sump pan, if that helps. The others are rear sump. The factory "batwing" 97-04 vette pan is pretty low profile, but is fairly wide. Would need to measure it and see if it fit between your stringers. The H3 Hummer pan is most likely too deep, and the truck and van pans are definately too deep.

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    Marine Power has both aluminum and iron LS motor center rise exhaust manifolds. They offer a nice LS motor marinized for I/O, jet and inboards (vdrives). I deal with John Troop out in Simi Valley Calif.

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    there are logs available for the ls motors priced between 650 and 850 from what ive seen

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    How about sustained high rpm's on stock LS components? Is anything special needed (oil pump mods, clearances, etc) outside of stock components or specs to keep them happy at 6,000+ for long periods of time like in jet applications?

    I'd like to stay away from stroker kits simply from an expense and longevity standpoint.

    Im glad to hear exhaust is now becoming available. From my standpoint with a mild 455, I could increase power and reduce weight by swapping to LS series engine. What is the approx weight difference b/t an aluminum block LS-1 and an iron 6.0 (LQ4, LQ9)?

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