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  1. #1

    What motor do I want?

    Here's the deal. I'm planning on building a jet boat, for running a shallow rocky river, using a PWC engine/pump, much like the one done here.
    http://www.tinboats.net/forum/viewtopic.php?f=21&t=8385

    I work very regularly with boats, mostly aluminum, and outboard engines, so I know the ins and outs with them. However, one thing I have never worked on, or really paid much attention to, is pwcs. Thus, I know nothing of the good models and bad models, or desirable vs undesirable variances, which is where y'all come into play.

    The boat I'll be using will be a 14 - 16 ft. aluminum flat bottom, or mod vee (jon boat shape, with some deadrise, which stays consistent down the length of the hull). The boat will have a bottom width between 48 and 54 inches, likely. Looking at something around the 650 - 800 cc range, 2 stroke. The motor in the above link was a Rotax 720, out of a '95 XP, and the owner has been thrilled with the performance. Aside from interior layout, my boat will be very similar to his, possibly a hare heavier, as I will be toting around 20 + gallons of water (bait tank - the main use of this boat will be for chasing stripers on the Etowah River, between Allatoona and Weiss lakes). I will be fabbing the intake and motor mounts myself (have TIG welding capabilities), as opposed to cutting the bottom out of a ski.

    Here's where my questions come in. I really have no knowledge of these engines. I do have much experience with two stroke outboards, and my father has plenty of two stroke motorcycle experience, so working on them will be no sweat. But, I'd rather not have a "lemon" design so to speak. I'd like a simple, reliable engine. Hence why I'm in the SeaDoo forum (I'm open to other brands, but y'all don't have a general PWC forum). I've heard that from the standpoint of reliability, as well as parts availability, they are the cats meow.

    I will be looking for a cheap battered ski to snatch the motor from, so I'd rather we narrow down the skis I don't want, as opposed to deciding on a perfect ski, which I may or may not be able to find for the right price.

    Given all this, what suggestions do y'all have?

    Thanks,

    bassboy1


  2. #2
    PEST!'s Avatar
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    An old Yamaha would be a better choice. Their pumps come out of the hull complete with the intake and all you would need is a bearing support between it and the engine. The old Yamaha 701 and 760's are bulletproof. You can go all the way up to the 98 1200cc but the 760 would be ideal INMHO

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by PEST! View Post
    An old Yamaha would be a better choice.

    Their pumps come out of the hull complete with the intake...
    Which Yamaha hull models would have that pump type?

  4. #4
    PEST!'s Avatar
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    just about all the old Yamaha. The 1997 Waverunner III is one that comes to mind it has a 701 engine and a bolt in pump

  5. #5
    Quote Originally Posted by PEST! View Post
    The old Yamaha 701 and 760's are bulletproof.
    That's what I like to hear.

    An old Yamaha would be a better choice. Their pumps come out of the hull complete with the intake and all you would need is a bearing support between it and the engine.
    On the one hand, that sounds nice, given the simplicity factor, but on the otherhand, fabricating my own intake has charm, given this boat will be running a shallow river that is known for eating boats (fairly young river, so the rocks haven't eroded smooth yet, and in the civil war, molten iron slag was poured in the river). I can a) make it much beefier than would a pwc pump be from the factory, and b) I can repair/replace it cheaper/easier.

    Say I went that route, what other skis should I be looking for, that meet the reliability requirements. Any particular ones to stay away from?

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