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  1. #1

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    785 project - restoration work

    Figured I'd start a new thread for the 785 project. Some pics of what I'm up against.

    Left side gunnel. Not quite sure what happened here, but she sure took a beating. I'm thinking the plan here is to epoxy in a couple slabs of fiberglass from behind, grind out the damage, build up with a couple layers of glass/epoxy on the outside. The question I have is what kind of filler/bondo can I use to finish off? Or is there something else I should be using?



    The back deck. Pretty straightforward repair. The crack had kind of de-laminated the glass, so I had to use a Dremel with a small burr to cut a groove down the crack and get it to sit flat. Added a couple sheets of glass in on the inside. I'm not real happy with how it laid down along the ridge, it didn't quite adhere like I wanted, but it should be good enough. SUPER awkward area to try and work in. Temporarily screwed on a chunk of wood to the outside to hold everything level-ish. The plan is to stand it on its end and use some 4lb density expanding foam to reinforce. Same as above, going to bevel the area back with a flap-wheel and build up a couple layers of glass/epoxy on the outside.



    Where else I'm a little lost is on these kind of cracks. It looks to me like it's just the gelcoat, or maybe the outside layer of the SMC? The plan was to use the burr to cut a shallow groove into them, then just fill with a non-reinforced body filler. Is there something else I should be using instead?

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    Last edited by pascoea; 09-24-2022 at 02:36 PM.

  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Sorry, I'm not a body guy. Hopefully someone else who does know will chime in.


  3. #3
    Myself's Avatar
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    For filler you could use 'Marglas", 'Pro-glass" or 'Duraglass"....all waterproof. 3M also has a waterproof marine filler. I use Pro-glass because it's what the local body supply has in stock. I've also used both the other brands with no issues. I mix in 1/4" chopped strand glass with my epoxy resin for deeper or larger fill areas. The dremel with a sanding roll makes a nice groove to fill in all those gel coat stress cracks. If you don't.....they WILL be visible after paint! You really need to get it as close to smooth as possible without any other types of filler. It's totally do-able but it uses a lot of sandpaper cause the high resin content clogs it up. Then I go over the whole thing with a 2k filler primer. It even comes in spray cans now with the catalys built into the bottom of the can......you just pop it on something then shake it up! Light sanding marks and pinholes will fill up with a couple passes of the 2k primer. And after a couple days it wet sands flat pretty nice without clogging the paper too bad.

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  5. #4

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    Quote Originally Posted by Myself View Post
    For filler you could use 'Marglas", 'Pro-glass" or 'Duraglass"....all waterproof. 3M also has a waterproof marine filler. I use Pro-glass because it's what the local body supply has in stock. I've also used both the other brands with no issues. I mix in 1/4" chopped strand glass with my epoxy resin for deeper or larger fill areas. The dremel with a sanding roll makes a nice groove to fill in all those gel coat stress cracks. If you don't.....they WILL be visible after paint! You really need to get it as close to smooth as possible without any other types of filler. It's totally do-able but it uses a lot of sandpaper cause the high resin content clogs it up. Then I go over the whole thing with a 2k filler primer. It even comes in spray cans now with the catalys built into the bottom of the can......you just pop it on something then shake it up! Light sanding marks and pinholes will fill up with a couple passes of the 2k primer. And after a couple days it wet sands flat pretty nice without clogging the paper too bad.
    Thank you for the thorough answer.

    I had a suggestion on another forum (Facebook group) where a person was suggesting they wouldn't attempt the repair without splitting the hull. Any thoughts on that? They were specifically referring to the gunnel repair. My intent was just to dig the existing foam out of there, do my best to get a couple layers of glass/epoxy in from behind, then complete the repair from the outside. (Reinforced with 4Lb density foam once it's done.)

  6. #5
    Myself's Avatar
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    You can do that WHOLE repair from the outside. Grind/cut out the damaged glass. Use spray foam from behind to 'fill' in the void. Carve the spray foam out just under the edges so you can stuff glass down under the edges in a 'from behind' lip type approach. Brush epoxy resin into the foam and let it set up first. That will harden and seal the foam. Then add in your glass feathering out the edges. Smooth out the top and done.

  7. #6

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    Quote Originally Posted by Myself View Post
    You can do that WHOLE repair from the outside. Grind/cut out the damaged glass. Use spray foam from behind to 'fill' in the void. Carve the spray foam out just under the edges so you can stuff glass down under the edges in a 'from behind' lip type approach. Brush epoxy resin into the foam and let it set up first. That will harden and seal the foam. Then add in your glass feathering out the edges. Smooth out the top and done.
    Thank you.

  8. #7

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    Finally got the rest of the crap out of the hull, gave it a good de-greasing and power wash. Didn't come quite as clean as I'd like, but HUGE improvement. Uncovered a couple areas of concern that are going to be addressed:

    Looks like I'm going to have to do some light repair work underneath the ebox (?) mount:


    I need to do some more investigating to figure out if it's just the epoxy coating that's cracked, or if it's lifting out of the glass.

    Next one, up underneath the gas tank mounts, bit of degradation of the fiberglass, and a bunch of the coating came up.



    What would a guy use to repair/recoat it? My intent is to clean up and re-coat the entire interior once I'm done with the repairs.

    Lastly, the trim motor... It was pretty nasty inside, but I was able to get everything cleaned up and moving. I don't trust the motor though, too far gone. The sticker in the picture appears to be Polaris markings, not the part number of the motor itself. There was another sticker on the back of the motor, I assume it was the actual part number, but I couldn't read it. Based on a FB post it looks like a Mabuchi RS-555SH 12v motor is the proper replacement, so I have on of those on the way. Anyone have a clue what the difference between the 3RPM (slow) and 6RPM (fast) trim motors are? Is it just the actual motor, or is the gearing different? I only ask because the post I found was the "fast" motor, so I have no clue if changing this motor out will turn it to a 6RPM motor or not. (EDIT: For anyone that comes and finds this later... Here's a good thread on rebuilding these: http://greenhulk.net/forums/showthread.php?t=220252 )

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  9. #8

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    I was short a couple of parts: MFD Core, Trim Box, a drive shaft, some pump parts, some random bolts, a stator/flywheel, starter, and a control PCB for the 900. So I found a better solution. Meet the newest member of the fleet, everybody's favorite, the "donor ski".



    $450 bucks, delivered, with a trailer.

    Cosmetically, the hull is pretty tough, but quick look appears to be structurally sound. Motor was delivered in pieces, so no clue what I've got there. I figured if I can get half the parts I need out of it I came out ahead.

    (I replaced the motor on my original trim box, as outlined above, and it promptly gernaded. Not sure if I screwed up or what, but it broke a shaft and stripped a couple gears)

    As you can tell from the amount of leaves, the "thinking about jet skis" season is about over up here, so we'll mostly be picking these projects up next summer. I might start the 785 engine rebuild over the winter, but it's time to turn attention to my other hobby:

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  10. #9
    Ryan Beernutz's Avatar
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    I know where I'll be taking the wife to look at lights this winter... the only problem is that she'll question how I know about them!

  11. #10

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    Quote Originally Posted by Beernutz View Post
    I know where I'll be taking the wife to look at lights this winter... the only problem is that she'll question how I know about them!
    Ha, no need to explain, just "happen" by. There are a couple people around here that put up some decent displays.

    I usually have everything up by Thanksgiving, but probably won't have music incorporated till closer to xmas. If anyone else wants the address (Ramsey, Northwestern Minneapolis suburb) shoot me a PM.

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