300sx Small Pin 750 Conversion Build
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  1. #1
    PWCToday Newbie rhyno857's Avatar
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    Oct 2017
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    300sx Small Pin 750 Conversion Build

    I started a more ambitious build this winter due to my 88 JS550 build going so well. My brother came across a couple 300sx hulls and ended up giving one to me. I tracked down a 750ss a few hundred km's away and decided to attempt a 750 conversion. I've been picking away at it over the past couple months and decided I should make a build thread. I'm pretty bad at taking pictures to document my builds (that's what happend last year with the 550) but I'm going to force myself to pause and take pics along the way this time. I've read pretty much every thread that you can search on here regarding 300sx conversions so I've done my homework. The SS hull was not pretty at all when I picked it up, the guy did a "paint job" on it and decided to use a mini grinder with a sanding disk to strip the paint off so it kinda looked like someone painted a golf ball black with a coarse brush. Didn't take any pics to save people the hurt I felt when I first saw it. Needless to say I didn't feel to bad about cutting it up. Everything else was pretty good on it part wise and I was really happy with the condition of the engine. I stripped the 300sx down, stripped the turf off, did up some measurements, zipped the tray open and defoamed it. Just finished the rough defoaming last night, working on getting the hull cleaned up good before I start getting into the reinforcing work. I've been picking away at other things the past few weeks as well. Made up a few Ebox plugs to fill the places of the heat sensor and fuel level sensor wiring that I removed. (is it ok just to unplug them or are there any that I have to cross for the wiring to be correct?) Also have been working on some jigs and fixtures for the motor mounts and pump alignment. My plan at first was to splice the pump tunnel and motor mounts as one piece but due to some genius using red loctite on all the hardware in the SS (which made it a nightmare to get the engine out) I broke off some bolts in a few of the mounts. I tried getting them out but it was mess so I decided to just splice the pump tunnel and machine up some engine mounts. I'm a machinist by trade with access to a CNC mill/Lathe and CNC punch and my brother is a welder so making parts is not a concern. I've been picking away at the engine mount design on my lunch breaks but just need mount height. That's pretty much where I'm at right now, hope I kept a few peoples attention. Any help or insight would be appreciated, I'm no pro so I'm sure I'll be asking some questions or if you just want to follow along that's cool too. The goal for my build is to make a fun "freestylish" ski due to the small pin having more bottom end but keep the 300sx look. I'm not planning to build a race machine or mod the hull too much so I'm not concerned about max top speed. Here's a few pics on what I have going on so far, my cat likes to help so he'll show up here and there.


    IMG_20181121_203140_053.jpgIMG_20181201_130441_1.jpgIMG_20181201_082838.jpgIMG_20181215_122452.jpgIMG_20181215_130317.jpgIMG_20181219_165052.jpgIMG_20181219_165106.jpgIMG_20181214_123742_865.jpgIMG_20181220_080943.jpg

  2. #2
    PWCToday Regular Meeker78's Avatar
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    Apr 2016
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    Oregon
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    Re: 300sx Small Pin 750 Conversion Build

    I love seeing these builds. Good luck to you! It’ll be quite the undertaking. Do your research and you should be fine. Keep us updated here. Subbed

  3. #3
    PWCToday.com Is My Home Away From Home BLRider's Avatar
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    Re: 300sx Small Pin 750 Conversion Build

    One thing you should know about the pump tunnels on couches (like your SS) is the pump is recessed an extra inch into the hull. This will raise your tray height that same inch if you were going to use any of the SS hull surface when doing your pump graph.
    Never argue with an idiot, they will drag you down to their level then beat you with experience.

  4. #4
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: 300sx Small Pin 750 Conversion Build

    That shark mouth is awesome. I don't think I've ever seen one that big relative to the whole ski, lol. It helps make the ski look even smaller and more piranha like.

    Looking forward to this. I rode a 300sx for the first time this summer, and all I could think about was how fun one would be modded up.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
    3DR hull mods [TBD]



  5. #5
    PWCToday Newbie rhyno857's Avatar
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    Oct 2017
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    Nova Scotia
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    Re: 300sx Small Pin 750 Conversion Build

    Meeker78 - Thanks, I've been dreaming up this build for a while now. Glad I came across the parts to start.

    BLRider - Thanks for the advice, my rough measurements showed about 1/2" rise but its good to know it will be up to 1". Looks like I'll be losing a bit if the tray depth so I hope that wont affect riding/handling too much.

    theVetteman3 - Yeah man, I'm digging the paint job as well. Someone put a lot of work into the paint at some point in its life. I'm going to have to redo it but I'm really thinking on keeping that style. I was tossing around the idea of trying to get some stockish decals and make a sleeper but the shape and lines of the 300sx make for a good predator fish look. Hope I can find someone local to do some airbrushing when the times comes.

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