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  1. #1

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    Thrust to weight ratio of classic 2 strokes

    I am considering a rebuild of several X4s. I like the idea of strong bottom end and carving up the water with a small craft. I created a spread sheet to analyze several factors: weight of the craft, 1/2 full fuel tank, weight of the rider (me, 220lbs) divided by horsepower. The number is total weight divided by hp.

    My 2000 GTI gets a 10.1
    97 GTX: 7.6
    98 GTX LTD: 6.9
    The 96 XP: 6.2
    97 GSX LTD: 6.0
    2001 RX: 6.8
    2014 Spark 60hp: 10.8 (Don't miss the fact that an old GTI beats the base model spark)
    2014 RXT-X aS 260: 4.8 but EXPENSIVE

    Yam
    GP1200: 5.5
    GP1200R: 5.7
    GP1300R: 5.4

    Help me out here.
    1. What am I missing? I know, I know: No top speed in the 60's or 70's, but man, the water hurts at that speed.
    2. Why aren't there shops all over rebuilding these classic, carbed 2 strokes? GroupK seems to think it is a good idea.
    3. Can't we make these classics stone reliable with aftermarket electronics and a quality rebuild?

    Thanks for the input


  2. #2
    There is more to it than hp to weight. I will prefer an x4 over an rxp any day. The larger watercraft have become barges, and are great for top speed. It all comes down to where you ride. I would prefer a smaller craft even if it has less power and top speed because I ride on a small lake. If you ride on a large lake with lots of large chop or the ocean, an x4 would not be great. The older watercraft can be reliable with a little preventative maintenance. I ordered a spark HO. I think that will be the ticket.

  3. #3
    thetolleyman's Avatar
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    I agree totally. Been riding, repairing, rebuilding, and restoring classic two strokes for 20 years. The definition of old and classic has changed over the years, but I still love em'.

  4. #4
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    Quote Originally Posted by Wire4Money View Post
    There is more to it than hp to weight. I will prefer an x4 over an rxp any day. The larger watercraft have become barges, and are great for top speed. It all comes down to where you ride. I would prefer a smaller craft even if it has less power and top speed because I ride on a small lake. If you ride on a large lake with lots of large chop or the ocean, an x4 would not be great. The older watercraft can be reliable with a little preventative maintenance. I ordered a spark HO. I think that will be the ticket.
    Its more than just top speed, some folks like to take long trips...I prefer a larger 4 stroke water craft...better fuel economy, comfort and storage...

  5. #5
    SURFnTURF's Avatar
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    And some just dont have the skills to ride 2 strokes,usually they are smaller will tip over easier and 2 up riding can be very hard

    4 bangers are barges ,you can stand on the side of these things without them tipping over they plow through the chop

    Relatively new riders can be a jet pilot captain in a matter of seconds as they are so stable and forgiving

    And they are more fuel efficient and less maintenance

    But hey they are not for me and our group of riders, we ride surf 95% of the time and never see 4 bangers mixing it up in the rough stuff

    They sit on the outside watching because they are a handful in the surf and cannot match it with lighter faster 2 bangers

    But if you have a family they can be great for all.

  6. #6
    diamondwatercraft's Avatar
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    I think the reason you don't see shops rebuilding those 2 strokes is because they cant make any money on them. The 2 strokes are so cheap now that if you have someone work on it you end up putting more into it than its worth. Not many will put 2000 into a machine that's worth 2500.

    Reliability is getting to be a challenge especially when the machines are getting so old. They are not made to last forever. Breaking down on a Sat afternoon sucks. Can ruin your weekend quickly.

  7. #7
    CJ's gpr's Avatar
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    Quote Originally Posted by SURFnTURF View Post
    And some just dont have the skills to ride 2 strokes,usually they are smaller will tip over easier and 2 up riding can be very hard

    4 bangers are barges ,you can stand on the side of these things without them tipping over they plow through the chop

    Relatively new riders can be a jet pilot captain in a matter of seconds as they are so stable and forgiving

    And they are more fuel efficient and less maintenance

    But hey they are not for me and our group of riders, we ride surf 95% of the time and never see 4 bangers mixing it up in the rough stuff

    They sit on the outside watching because they are a handful in the surf and cannot match it with lighter faster 2 bangers

    But if you have a family they can be great for all.
    +1

    Old school skis are where its at. a friend of mine has an fzs and we can get 2 or 3 guys standing in a footwell without that thing tipping. everytime my friends get on my gp1300 they nearly flip the thing sitting still. the balance is just something that comes to you after riding stands up and these tiny skis for so long.

    I also agree with diamond though. the reliability with these engines worries me sometimes. I'll never ride the ocean alone because the truth is they are not made to last forever and THEY WILL BREAK DOWN.

    Now dont get me wrong the 4 strokes are nice to cruise with sometimes and i have gotten pretty good air on the vxr, but really it doesn't compare to that feeling of being 10 feet in the air on a little ski.

  8. #8

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    I did a comparo before..

    i took the manufacturers advertised weight, and horsepower, (had to guess for yamaha), and I did not add the fuel weight in, because I wasnt certain if the listed weight was dry, with no fluids, or with half tanks, or what.. so I added a 250 pound correction, for a rider, gear, and maybe some fluids here and there.

    I didnt factor in Thrust, which is really what we want.. we want Thrust to weight ratio.. I had no way to get the thrust numbers for most oems.



    HP Weight lbs w/ 250 lbs gas capacity hp / weight w/ rider
    seadoo rxt-260 260 824 1074 16 0.32 0.24
    kawasaki ultra 300x 300 1040 1290 20 0.29 0.23
    seadoo gtr-215 215 765 1015 16 0.28 0.21
    yamaha FZR 210 809 1059 18.5 0.26 0.20
    yamaha VXR 185 728 978 16 0.25 0.19
    seadoo Xp-DI L1 147 562 812 14 0.26 0.18
    seadoo gti se 155 755 1005 16 0.21 0.15
    seadoo Spark 90 90 450 700 8 0.20 0.13
    seadoo Spark 60 60 350 600 8 0.17 0.10

  9. #9
    Myself's Avatar
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    I'll stick with my lightweight 2 strokes. Easy to throw around, and they run plenty fast. PLUS...I can rebuild my whole engine at least twice for the cost of 1 minor overhaul of a four stroke ski. And if you wrench on skis on a regular basis you know, you can't EVEN throw in a reliability arguement, it's just not there compared to cost of operation.

  10. #10
    You cannot generalize this topic since people have different riding objectives. (Lake cruising vs ocean surf jumping are two extremes, one ski doesnt work well for both..)

    I went 4 stroke several years back. For our purpose (family, lake cruising) they are just so much more reliable and easier to own and use, especially no messing around with expensive oil. Just put gas in them. No whining from the family that the ski won't start. Just get on, push the start button and they go. A LOT cheaper to run, like half the gas. Less time filling up with gas.

    The only regret I have is that I didn't switch to 4 stroke a lot earlier than I did.

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