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hey bill heard u have done several 787 swaps in the hx do u use a special plate or glass in the front mount me and my girlfriends dad have started the project and its turning out good just was wondering how u did it and if u had any pics that would help us.
Most who are doing it today, are using a completely different mounting system than what we were using back in 1995 when we used oem hulls the first year.
Most guys today are doing it one of the two ways that it can be accomplished. One is grinding out the fiberglass inner liner for the oem front 787 mount and placing an aluminum plate embedded into the hull liner, then fiberglassing it in there in the proper position after tapping holes in it to macth an oem front 787 mount. There is two different hieght front mounts available from Sea Doo. A three seater model ( not really sure which model GTX it is, as maybe one year is different, or maybe it comes from a RFI model. I have never seen the mounts side by side ) is shorter than the GSX or XP by a little, and will give you space to lower the front of the motor for better alignment. It is imperative that you use and alignment tool to detirmine at what depth the embedded plate is to be able to get the engine to align properly, because if the front of the motor is too high, you will have driveline coupler issues. If you choose that route, you must know the ends and outs of using fiberglass woven cloth, not the fiberglass matting materials, and how to properly mix a very good grade of resin with just the right amount of catalysts so it will be strong. The aluminum plate needs to be fairly oversized to spread the loads and have a better bond with the fiberglass holding it in place. The woven 'glass should be layered in two directions as you put in layer after layer over the aluminum block, and it must cover an area much larger than the aluminum plate to be blended into the regular oem inner liner, everything ground on a taper so each new layer of 'glass is slightly longer and wider than the one under it.
You really need to think this method out in order to embed a plate and re-enforce it properly so as not to weaken the inner liner of the hull, as it is critical to the overall strength of the hull because the front of the hull will want to flex upwards when subjected to harse landings from jumping waves or bashing through rough water or waves and such even more than normal with the heavier and faster 787 engine up there.
The other method is an aluminum strap-like cradle piece, bent and shaped to use the oem 720 hull mounting positions on each side of the motor, then is shaped to drop down and connect with the front mount bracket on the mag housing to make a solid mount without rubber like a normal mount. I personally do not care much for that way of doing it for two reasons, first is the flexing of such a strap if not built correctly, and second, as you will need to grind away some fiberglass along side of the engine and reglass that part of the inner hull liner to clear most good aftermarket pipe exhaust chambers, why not go ahead and 'glass a permenent front mount plate into the liner at the same time ?
You do know the two rear 727 mount points in the liner are not exactly where they need to be for a 787 rear engine mounting cradle ? A couple of aluminum straps one for each side of the engine that will bolt to the embedded mounting points for the 720 engine, to offset the mounts for the 787 engine to properly be bolted to the engine's rear mount cradle. These two straps are fairly simple to make.
Be sure you have everything needed so that you can properly find the heights of where eveything needs to be to be able to get proper alignment of the engine, couplers, driveshaft and pump. You should figure into this room to use shims between all three mounts, including the mouting bracket on the mag housing, and the two rubber rear engine mounts and either the hull mount strap or the top of the rubber mount and the steel rear engine mounting bracket. You can always shim the engine up, but lowering it is nearly impossibe if the embedded front plate is too high, or the two adapter straps are too thick.
To make this easier for you, search this website archives for threads and pictures of the ways most guys are using today. I know HydroX and others' have posted pictures and instructions of how to fabricate the necessary straps and front mounts to do this job fairly easily.
Nowadays, at our shop, we use a specially made or modifed hull from Watoosee that has the proper mounting points built into hull liner before it leaves Jerry's shop, and we install our 787's just like as though it came oem that way.
hey bill i just want to say thanks for all the advice i also spoke to chris at your shop and he helped alot it should be done soon and i will send pics on the progress thanks again
Look up Water Worx in the "Advanced Search" function. He has a how-to posted for HX 787 conversions. He makes special plates for the rear mounts to allow the 787 bracket to mount up flush to standard 800 motor mounts. He also shows you where to cut, how to place in the front bracket, etc. Excellent write, highly recommend it.
*******THIS IS JUST A POST OF WHAT I DID TO MY BOAT AS REFERENCE ONLY, I ASSUME NO RESPONSIBILITY FOR WHAT YOU DECIDE TO DO TO YOUR BOAT************OK, first get a pump alignment tool and install it in the hull. This is all done best with an 800 short block and 720 out of the hull. Take the rear engine mount from the 800 and flip it around. You may need to open the holes up in the rear mounts to help alignment, not the case mounts!. Take the stock front motor mounts out of the stock HX hull and set them aside, you'll use some parts of them later. This is where the fabrication starts. Look at my pics. I used a piece of steel but aluminum will also work. Take the stock battery box out. Make a template out of cardboard, I used a case of beer box. LOL I did! Fashion a mount similar to what you see. The plate sits flush to the hull on the front engine mounts,(some filing flat of the fiberglass in front of the mounts will be needed). Here is where you start "real" fiberglass work. Cut a slot in the hull directly where the stock battery box was right where the "V" is so you can slide an aluminum plate in. About the size of the stock batt box bottom. To clarify, the aluminum plate is going to sit in between the lower hull and "grey" inner hull. Clamp the aluminum plate in between the hulls and drill and tap 4 holes. Do the same with a piece of steel on top of the same size. Bolt them together. refiberglass the slot you cut out. Approx. one inch by three inches. THAT'S ALL THE FIBREGLASS THAT NEEDS TO BE DONE!
By now the short block should be in and somewhat centered but tilted down in the front. Prop the front plate you made up until the alignment tool goes into the pto freely and straight. Use one of the frount rubber mounts only as the frount mount of the 800. After aligning drill and tap the holes for the front. Some shimming of the mounts will be necessary. Now cut another piece of steel to put in vertically as the gap filler between the front engine mount plate (big) and the battery boxed sized plate that you drilled glassed and bolted in earlier. Keep in mind that everything should be placed in loosely and tacked before final welding. There is a picture of the actual template I used except the "battery box" plate is longer than what shows in the pic, but you get the picture. 3/8 plate, the rise is about an inch, 8mm bolts in the "batt box" plate, and 1/2 inch aluminum plate sandwhiched between the hulls, stock front motor mount bolts to bolt to the stock motor mount holes, stock rear mounts.
The only thing that I don't remember is mounting of a pipe. I had a billett piece made that I swore I would never show from a manufacturer that sponsored some pro sport boats back in the day and it has their name on it and they told me never to show it so that is why the glove is on it. SORRY. I know I had the stock pipe on it for a mock up and I made a piece out of steel that bolted to the ex man and was "twisted" bolt hole wise a certain amount of degrees to angle the pipe upwards so it can clear the hull using counter sunk stainless bolts and two stock gaskets.
Mount the small electrical box to the front as shown and batt box where the oil tank was. Cables all seemed to reach fine.
This boat rips and jumps and the extra weight can be trimmed out. I have been running this exact boat for over ten years with no problems on the lower Lake Michigan shores (big fall waves!)
******THIS POST IS TO BE USED AS A REFERENCE ONLY**********
thanks everyone for all the replies this is all helping get this ski done the only problem im having is money issues so getting a alignment tool is the only problem im having right now so as soon as i get one i think this ski will be in the watter in no time the plate in the front instead of glassing in the mount is awsome i am gonna try that and see where it goes from there once again i wanna say thanks for all the help on this build
I have one of those "stealt pipe spacers" too for offsetting the pipe. Had three at one time years ago. The other two went with the boats when we sold them off after the season and built new carbon fiber boats that don't need the offset spacer or any special 787 engine adapters, as we build the hull inner liners ourselves to accept 787 engines.
ok well we finally got the engine in the ski just had a couple of questions. how do i hook the mater lines up i marked where they were in the old ski (97) xp but how do i hook them up in the hx i know the one from the top of the pipe went to the side so the ski so i put that one in the same place as the it was in the xp(pic 3) . There was one comming from the water box to the pipe with a valve in the water box i dont know what to do with that one (pic 1). And the two that come to a T at the bottom of the jugs just went to the back of the ski and out so i did the same with that. the two at the back of the head i know are the inlet and outlet for the water comming from the pump i believe they are hooked up the same as the 717(pic 2).
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