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  1. #1
    Click avatar for tech links/info K447's Avatar
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    Arrow Reinforcing the GP1800 hull at intake grate rear bolt/brackets

    The GP1800 hull seems at risk of cracking where the four rear intake grate bolts go through the hull. This is what I did to reinforce the GP1800 hull.

    To get down to the bottom of the hull inside, first remove the seats, then remove the five bolts holding the seat base to the hull. Use a second wrench to hold the brass nuts on the underside of the seat base. Do not drop the washers or nuts into the hull. Set the seat base aside.

    Now remove the stock exhaust resonators. The smaller upper resonator is held in place with a single gear clamp. Loosen clamp, the wiggle and pull the recount or forward until it releases from the big exhaust rubber U tube.

    Next loosen the gear clamps holding the big exhaust U tube to the water box and to the top of the large resonator. Wiggle it off the water box and then lift it up and out of the resonator. The resonator end of the tube extends deep down inside the resonator so it needs to be lifted up quite high.

    Right behind the big resonator loosen the gear clamp for the exhaust exit tube. Wiggle the big resonator free from the exhaust exit tube.

    Remove the big resonator from the hull. I found that it would only come out in one orientation. It is an odd shape but it will come out without heavy force. I don't have a photo, but I rotated the resonator vertical with the right side more forward in the opening, to avoid binding with the water flush fitting. A little wiggle and tug and it comes out.

    Lift out the white foam support that straddles the pump intake. Set it aside but don't forget to put it back in during reassembly.

    Next I disconnected the three hoses at the jet pump. Each had white sealant groped onto the hose clamp. Hose clamps are the spring type, use pliers to squeeze the tangs together and slide clamp along hose, then wiggle hose off the metal nipple

    Note that all the hoses and fittings are the same size, so I labeled them.


    I left the steering cable in place - too much trouble to remove and I could work around it.

    You will see the two cast metal brackets for the intake grate rear bolts. One bracket on each side of the jet pump intake. Globbed on top will be a large dollop of brown glue. The bulk of this glue needs to be removed, then the bracket can be popped loose from the sealant underneath.

    I used a combination of an electric heat gun, various pliers, and tearing chunks of glue away until most of it was gone. Do not pry aggressively against the liner/hull material to get the glue off. The hull material can be gouged/damaged by screwdriver stabbing and prying.

    With the glue mostly gone, I removed the intake grate from below the hull. Six bolts, two at front, two on each side. Set the intake grate aside. I reinstalled the four rear bolts about 1/2 way in, then used a dead blow hammer to whack upwards on the bolt heads. A few solid taps was enough to lift the factory brackets inside the hull away from the sealant.

    Remove the bolts, then remove the factory brackets from inside the hull.

    I cleaned the remaining sealant and glue fragments from the inside of the exposed 'pockets' using careful scraping and a razor blade tool. Tedious work, with awkward access. The factory hull liner is cut away here, so you are working directly on the inside surface of the NanoXcel 2 hull material.

    I chose to fabricate aluminum 'spacer blocks' to sandwich between the hull and the aftermarket reinforcement plates. 3/8" aluminum cut to approximate shape, then an angle grinder to round off the corners to fit.

    Where the inner liner is cut into the vertical side of the pump, I found the gap to vary, sometimes there is glue 'squeeze out' that gets in the way. More careful work with a razor to trim the glue bead as needed.



    Several test fits later, the aluminum spacer plates fit into the opening and sit flat and flush against the outer hull. This is important, there should not be any debris or bad fit to cause the spacer block to not sit flat.



    While a helper holds each plate firmly in place, I went under the hull and drilled small 'marker holes' directly through the middle of the holes in the hull. Each plate was marked with which side it came from and which side is 'up'. Remove plates, then drill large enough holes that will easily clear the 8mm intake grate bolts. The holes need to be large enough to provide some wiggle room.



    Place the aftermarket reinforcement plates inside the hull, then position the intake grate and test fit the new, longer bolts. The front two intake grate bolts will remain stock. For the rear bolts I found 45mm length was about right. I used 8mm bolts that were threaded full length.

    The supplied 8mm bolts with the plate kit would not work for me as the unthreaded shank portion was too long. If you want to add lock nuts on top of the installed plate then you may need 50mm or 60mm bolts.

    Note: If your installation uses a thicker spacer plate or a thicker build up of epoxy/fiberglass then the kit bolts may work just fine. Just be sure the threaded portion of the bolt does not bottom out against the threaded kit plate.



    I found that the hull liner material on the sides of the pump tunnel was bulged outwards slightly, just enough to interfere with the alignment of the bolts holes in the kit plates. Rather than attempt to shave the hull liner, I trimmed just enough metal from the side of the reinforcement plate to allow the holes to align with the hull holes and the intake grate holes.

    All three holes must align, and the intake grate must end up correctly positioned under the hull. You do not want the intake grate to be canted or twisted out of alignment with the hull when the install is finished.

    This is made more tricky as the wide segmented rubber seal between intake grate and ride plate prevents the intake grate from being easily removed or reinstalled while the ride plate is bolted up. If you are working with ride plate removed, be sure to get the intake grate position exactly right. Once the epoxy hardens there will be no adjusting those bolt holes later.



    Note the gap between hull liner and the colored reinforcement kit plate. The gaps will be filled with West System epoxy, reinforced with glass Microfibers.

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    Last edited by K447; 04-30-2018 at 08:09 PM.


  2. #2
    Click avatar for tech links/info K447's Avatar
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    Now comes the messy part.

    Make sure the intake grate is properly positioned/aligned and the front bolts are quite snug, as well as the rear intake grate bolts on each side. Remove the two bolts on just one side.

    Lift out both metal plates on that side.

    We used three pumps of West System epoxy from each can into mixing cup, then added enough filler to make the mixture fairly thick and gloppy. The idea was to not have it drool and run out of the work area. The epoxy working time is limited to minutes once it has been mixed together.

    i packed epoxy along the gap below the vertical liner, and all around the perimeter where the liner is cut away. A thinner layer of epoxy smoothed on the flat hull. You do not want a lot of excess epoxy forced down through the hull holes. That would just make for more work later, cleaning off the hardened epoxy under the hull afterwards.

    Now the spacer plate is dropped into place and position adjusted to align the plate holes with the hull holes.

    More epoxy is thinly smeared on top of the spacer block. And lots of epoxy packed around the exposed sides of the spacer plate, especially at front and rear. This perimeter epoxy bead is what the reinforcement plate will sit on to transfer water loading/stress from the intake grate bolts to the hull liner, and to an overall much larger hull area than the factory brackets.

    You may want to lightly grease or wax coat the bolt threads near the head, so the epoxy won't stick directly to the bolt. Or coat all the threads, and be sure to use the lock nuts after completing the reinforcement plate installation.

    Place the reinforcement plate plate on top of the epoxy sandwich. Adjust for hole alignment and thread the longer bolts up from below. Don't forget the flat washer and lock washer on each bolt. Snug the bolts firmly. Do not over-torque.

    There should be squeeze out on all sides. Against the vertical pump tunnel the epoxy should fill the gap between spacer block. For the top reinforcement plate, you want epoxy filling the entire space down to the pump liner on the outside edge and especially front and back. Pack more epoxy into the space as needed and reshape using the brush/applicator as needed to make it look tidy.

    Repeat on the other side.

    Photos to follow...
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    Last edited by K447; 07-26-2017 at 08:41 AM.

  3. #3
    Decided against using Marinetex? Why use an aluminum plate as a filler? It seems like it's elevating the red ultramax plate pretty high off the liner. You really need some good bond in that depressed area as leaks may occur!

  4. #4
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by jetdawg701 View Post
    Decided against using Marinetex?

    Why use an aluminum plate as a filler? It seems like it's elevating the red ultramax plate pretty high off the liner.

    You really need some good bond in that depressed area as leaks may occur!
    The cut liner has uneven height around the opening. If the kit plate is to be parallel to the outer hull surface when fully installed, there has to be epoxy or similar to fill the inevitable gaps between plate and liner.

    I felt the 3/8" thick aluminum spacer plate would be stiffer/stronger in bending/flex than MarineTex or fiberglass+epoxy. This method also avoids needing to grind the thick layer of MarineTex semi-flat on top prior to installing the reinforcement plates.

    The aluminum spacer plate spreads the stress load across the entire exposed NanoXcel 2 hull area. The kit plate extends the support onto the hull liner via the epoxy packed under the perimeter of the kit plate.

    The thin epoxy layered between plate and hull and between the two plates fills any thin gaps. My expectation is that the bolts are now solidly held in position and the intake grate load onto the hull is sufficiently distributed that the hull material will not over flex (and therefore not stress crack) over time.

    Regarding water leaks, there should be sealant where the bolts pass into the hull. This was the factory location for the sealant. Note that the factory brackets have a metal shoulder that fits/centers into the hull holes. Using this kit method eliminates that shoulder so the bolt centering is dependent on the installer accurately locating the kit plate during assembly.

    It still surprises me that the factory bolt torque spec for the intake grate rear bolts is so modest. This implies that the expected stress in operation on the water is not high, yet the GP1800 hull (and appparently some VXR) is being stressed enough to create cracks at the intake grate rear bolts.
    Last edited by K447; 07-26-2017 at 08:45 AM.

  5. #5
    powerstroke specialist mikegp's Avatar
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    you have done what i had in mind all this time , a solid aluminum piece capable of filling the cavity and with the help of some heavy epoxy fill the gap in between the inner hull that way it will pull on the inner hull as one piece down .
    now that you have it on your hand think about going with one solid piece do you have anyone who can mill a solid piece?

  6. #6

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    Great write up. I need to do mine soon lol I have been putting it off. I like the idea of the aluminum but you dont think a well done glass job will be just as strong?

  7. #7
    Work Harder, Millions on Wellfare Depend On Us! ultramaxracing05's Avatar
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    I can do a solid piece for the bottom. Just need a template since I done covered mine up.

    Sent from my SM-G930V using GreenHulk PWC Performance mobile app powered by Tapatalk

  8. #8
    powerstroke specialist mikegp's Avatar
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    Quote Originally Posted by ultramaxracing05 View Post
    I can do a solid piece for the bottom. Just need a template since I done covered mine up.

    Sent from my SM-G930V using GreenHulk PWC Performance mobile app powered by Tapatalk
    get in touch with k447 he has them on hand . if you do make them a solid piece don't do them like flush with the hull , imo they need to be about 1mm from the top deck as well as the bottom deck to be able to fill with epoxy , pretty much as is you will be laying floor tiles ,to give you an idea.

  9. #9
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by mikegp View Post
    get in touch with k447 he has them on hand .

    if you do make them a solid piece don't do them like flush with the hull , imo they need to be about 1mm from the top deck as well as the bottom deck to be able to fill with epoxy , pretty much as is you will be laying floor tiles ,to give you an idea.
    I do not make the spacers for sale, i just made enough for my own hulls.

    My metal spacer was set into a thin layer of epoxy underneath, then it was squeezed out as the bolts were snugged to hold the assembly flat and in position. The epoxy remaining underneath fills any thin gaps but does not hold the metal spacer away from the hull surface.

    The metal top plate does sit a mm or two above the hull liner material. That air gap is filled with epoxy and provides the primary load bearing surface for the longer than stock hull inserts.

    UPDATE: The factory hull inserts from the FX SHO (and perhaps all FX hulls since 2004?) are the correct length and hole spacing to be used for GP1800 hull reinforcement. See this thread from Jerry for photos and more details.

    Other than using the Yamaha part instead of the aftermarket top reinforcement plate, the method for installing the reinforcement using the Yamaha insert (part number F1G-U8571-02-00) is the same as I have posted.
    Last edited by K447; 04-30-2018 at 08:31 PM.

  10. #10
    Any tips when filling the small voids between the top plate and the hull? I know you used epoxy but it seems it would just seep out of the gap no? Did you use additional 403 to act as a thickening agent to prevent seepage? Would using 404 be a good alternative as well? What about Six 10?

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