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  1. #1
    PWCToday Regular vocalDyslexic's Avatar
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    Kinda disappointed with a heavily modified 750

    This is the engine out of the sxi pro I had listed for sale, minus engine and electronics. I bought the ski for the engine and planed on selling everything else. Which will still happen eventually but unforseen hull issue has put the whole thing on hold. Anyway, I rode it several times and it seemed pretty awsome. I pulled the engine and ebox and installed in a new x2 project today. Took it out and well im kinda not sure how to describe the experience. Disappointed is about the only thing I can use. I bought back most of my sold x2 stuff for about 1/3 if what i sold it for, and took the 750 from the pro, and threw it all in new to me x2. Heres what I have currently:
    The 750 is a product of Newmiller Machine
    Ported big pin cases
    Ported small pin cyls
    Milled head @ 185psi
    +1mm wiseco prolites
    lightened flywheel
    Full FPP limited sxi setup
    46mm SBN on r&d small pin manifold

    It screamed in the 98pro.
    Inorder to swap i pulled the FPP setup bolted up my 650 westcoast exhaust manifold, a uncut coffman pipe system, and mounted the ebox.
    Played with the air fuel mixture as it ran great at idle, but would not rev out even unloaded. I ended up having to go about 1.5 turns in on slow circuit and 1turn in on high. And then there was BRAAAAP!, and it was good. Took to lake and it ran flawlessly, with one issue. It pulls nowhere near as hard as it did in the iPro. The pro even has a more top speed orienated swirl. I put the only skat i had for a 650, the 15.5 in thinking top speed will be alot less, but was under the impression that it should pull harder till it hits the x2 wall. It doesnt at all tho. Im trying to figure out what to do to change this. I understand the engine wont run the same now with the fpp gone and a 650 coffman on it, but there isnt alot of options there, unless someone knows how to get the fpp sxi limited pipe in a x2 without having to take a sawzall to the hull, or a plasma cutter to the pipe. Can the coffman hinder it that much, and if so why is that the top recomendation for a 750x2. Can the 46mm SBN be too much with the restricted 650 pipe or am i possible overlooking something simple I didnt do or do correctly in the swap? I know this engine is legit, i rode it a few times and it was a beast, and i have all the reciepts and invoices for all the work. Since it ripped in the pro, but is very ho hum/lackluster in the x2 im thinking its 650 coffman related but if so, that kinda blows knowing thats about the only option. I almost wanna put it back in the sxi and have a large cc powervalve twin built for the x2. But then im afraid if i do that im back with the very same exhaust option problem, right. I know this is probably the overly optimistic dream, but i would like a 125-150hp setup. This newmiller 750 has to be over 100 with the FPP, but in the x2 it seems only slightly more than the modded 650 that i had in my other x2. I am a fat azz and need a powerplant that can compensate for my poor eating habbits which is why im trying to keep increasing power till the power to my weight ratio is dramatically improved since that increase can take much less time than a decrease in my weight. Im open to any and all suggestions from diff engine options to the standard 'needs a yamaha engine' or recomending a set of p90x disks. Considering the 750 i have to work with do i chase more hp with 210+psi and $11 per gallon race gas, or abandon the 750 for something else and if so, what? I dont want a 1100x2 either, they barely seem to float before anyone even gets on them, and im sure most will disagree with this, but i would take a rotax951 over a kaw1100 without hesitation. If someone made a gen 1 top swap for a sxr hull, id build a 951x2, but here we are... i want modded out 951 level of hp in my gen 1 x2, so can it be done, or give up and buy a 300hp kawasaki ultra or a seadoo, and accept reality that im too fat to x2?

  2. #2
    PWCToday.com Is My Home Away From Home freekstyle's Avatar
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    Re: Kinda disappointed with a heavily modified 750

    Get rid of that 15.5 impeller!

  3. #3
    I dream skis
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    Re: Kinda disappointed with a heavily modified 750

    Yeah...that prop is holding you back. Opt for a v/p swirl.

  4. #4
    PWCToday Regular vocalDyslexic's Avatar
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    Re: Kinda disappointed with a heavily modified 750

    Thats the plan, it was just the only on hand peller. What would be the recommended size.

  5. #5
    Top Dog
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    Re: Kinda disappointed with a heavily modified 750

    impeller and the pipe is killing you.

  6. #6
    PWCToday Regular vocalDyslexic's Avatar
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    Re: Kinda disappointed with a heavily modified 750

    Whats the proper course of action to rectify. I knew the 15.5 wasnt gona be good top end, but i was under impression that it would be crazy quick. is the hp its making allowing it to spin the impeller quicker than the rate at which the impeller can move the amount of water causing a lack of loading of the pump? And what do i do pipe wise. Do i go back to the fpp setup and swap the sxi limited chamber to a _________ chamber?

  7. #7
    Top Dog Benflynn's Avatar
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    Re: Kinda disappointed with a heavily modified 750

    Rebuild sxi and put 701 in the x2, I built a decent low port small pin 750 for our x2, but think I'm going to put a 701 in it instead

  8. #8
    Top Dog Benflynn's Avatar
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    Re: Kinda disappointed with a heavily modified 750

    More power instead of loosing weight(me too) wears u the hell out fast

  9. #9
    PWCToday Regular vocalDyslexic's Avatar
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    Re: Kinda disappointed with a heavily modified 750

    Im looking at it like this. With more power will come more weight loss. The harder it is to stay on, the better the work out will be. The better the workout, the greater the weight loss. I appreciate the replys, but noone has yet answered what impeller to use, and what do i do about the exhaust.

  10. #10
    PWCToday Guru Bob Gruen's Avatar
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    Re: Kinda disappointed with a heavily modified 750

    I am a firm believer that the 750 engine needs a full 2" exhaust system to get the most out of it. This means: FPP Blaster Limited Pipe, 2" TDR baffled water box, and a custom 2" thru hull fitting, relocated to the nose. I did all of these things on my small pin (link in my sig) and it pulls hard on the low end and mid range but runs out of breath on the top end. I think a simple timing adjustment will fix it though. I am still on stock compression.

    That being said, my gen 1 Blaster, which has similar mods but bumped compression, pulls a good bit harder and runs faster on the top end due to the hull's much wider draft. X2s and Blasters ride very similarly (leaning into the turn), and a Blaster has enough room for a triple which is a common and well documented mod. If you decide to give up on the X2 due to your size, move to a Gen 1 Blaster.

    Bob
    Last edited by Bob Gruen; 09-28-2017 at 09:24 AM.

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