550 Exhaust Options
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  1. #1
    PWCToday Regular
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    550 Exhaust Options

    Hi all,

    A few years back I restored an 85 JS550 as a foray into engine building. The ski was a basket case with a blown 440 in it but with a smattering of aftermarket parts, some of which I ended up reusing. I got the ski together and after a lot of failed lake days and ironing out the kinks, I finally got it reliable, and finally had it water tuned by the Jet Ski Clinic at Antioch. It's been a great runner, plenty reliable and good fun, but it just doesn't have the powerband I expected. I can push it up to about 37-38mph on flat water but I expected more, and it never really feels like it hits that point where it truly comes into power like others I've ridden. It also runs fastest at about 80-90% throttle. If I squeeze it that last little bit it bogs out just a bit and I can't really seem to tune that little top end bog out. This winter I'm hoping to upgrade my exhaust setup, rebuild and blueprint the pump, and have it tuned again.

    Long story short, I think the exhaust setup I scavenged from the 440 that was in it is a bad match for my engine and prop setup. I'm looking to change it up to get a bit more power.

    My build list:
    • New trued and welded crank
    • 550 jug (unknown year) mildly ported. Widened each port 2mm, did not change port timing.
    • Fresh 0.5mm over Wiseco pistons
    • .030" shaved stock head
    • New SBN44 carb
    • Unknown Kerker-looking exhaust pipe (from 440 setup)
    • Unknown teal, cylindrical aftermarket water box (from 440 setup)
    • Skat-Trak 16* prop (I think)
    • Upsized cooling fittings/lines
    • OP ride plate, scoop


    So all you gurus, what exhaust setup would you put on this ski? I don't need a 45+mph race ski but a little more punch and maybe scraping 40 would be nice. Here are a couple pictures of the engine setup, plus a bonus shot of the ski. Thanks i advance for the help!





    Last edited by the_eskimo_wonder; 09-08-2020 at 02:50 PM.

  2. #2
    PWCToday Guru
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    Re: 550 Exhaust Options

    Your current pipe + the 16 degree prop are working against each other.

    I’d definitely recommend a Factory or Coffman half pipe (with the 86+ OE exhaust manifold).

  3. #3
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    Re: 550 Exhaust Options

    Quote Originally Posted by candysucker View Post
    Your current pipe + the 16 degree prop are working against each other.

    I’d definitely recommend a Factory or Coffman half pipe (with the 86+ OE exhaust manifold).
    So that would be the factory Jetpower exhaust manifold and 180 degreee header pipe, just minus the Jetpower box itself, right? Replace the Jetpower breadbox with the half pipe? All the exhaust options are a bit confusing.

  4. #4
    PWCToday Regular
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    Re: 550 Exhaust Options

    I guess if we're looking at this should I also be considering a different pitched impeller? The 16 came with the ski and I'm not married to it. I'll be switching up my exhaust either way but I'm almost 200 pounds and I'm assuming the 16 degree prop might be too tall regardless.

  5. #5
    PWCToday.com Is My Home Away From Home PrickofMisery's Avatar
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    Re: 550 Exhaust Options

    Quote Originally Posted by the_eskimo_wonder View Post
    So that would be the factory Jetpower exhaust manifold and 180 degreee header pipe, just minus the Jetpower box itself, right? Replace the Jetpower breadbox with the half pipe? All the exhaust options are a bit confusing.
    That’s correct.

  6. #6
    PWCToday.com Is My Home Away From Home
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    Re: 550 Exhaust Options

    if it's a short body pipe,get rid of it and replace with long body or oem pipe + 1/2 pipe.

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