Polaris sled/watercraft motor question. - HCS Snowmobile Forums

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Old 03-07-2012, 10:32 AM   #1 (permalink)
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Default Polaris sled/watercraft motor question.

I know there is plenty of info out there regarding the watercraft triple conversion, using 700/800 jugs for a 1050 or 1200 motor.

Has anybody looked into something smaller, based off the 440/500/600 smallblock jugs? Just curious. It seems to me something like this could be much lighter, more compact, and still toss up some pretty respectable HP numbers.
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Old 03-07-2012, 10:46 AM   #2 (permalink)
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Years ago my buddy tried building a 780 piston port triple using the watercraft rods only to end up in failure. Motors would produce close to 180 hp before twisting the crank. Tried a 150 hp trail version of it in a 95 xcr but never got more than a couple hundred miles on the motor before the crank failed.
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Old 03-07-2012, 11:09 AM   #3 (permalink)
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Quote:
Originally Posted by warpspeedxcr View Post
I know there is plenty of info out there regarding the watercraft triple conversion, using 700/800 jugs for a 1050 or 1200 motor.

Has anybody looked into something smaller, based off the 440/500/600 smallblock jugs? Just curious. It seems to me something like this could be much lighter, more compact, and still toss up some pretty respectable HP numbers.


regardless of cylinder you use the dimensions of the motor from pto to mag is going to be the same.the watercraft cases are big.add the stator housing you need on top of that with the pullys and they are 4-6"s wider than an xcr8.the watercraft triple cranks however if using the xc 800 70mm stroke or the xc 700 68mm stroke are very beefy cranks.they make the xcr 8's crank look like a twig.with that being said now you could use smaller jugs on the cases if the patterns will bolt up and bore and stroke combos are available.you could always have brad make you a custom crank of the stroke you want.on SW forum there was a thread were a guy weighted his 1200cc watercraft v.s ultra 680.there was only 15lbs difference in the motors weight wise and the 1200 is almost double the displacement.
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Old 03-07-2012, 06:52 PM   #4 (permalink)
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regardless of cylinder you use the dimensions of the motor from pto to mag is going to be the same.the watercraft cases are big.add the stator housing you need on top of that with the pullys and they are 4-6"s wider than an xcr8.the watercraft triple cranks however if using the xc 800 70mm stroke or the xc 700 68mm stroke are very beefy cranks.they make the xcr 8's crank look like a twig.with that being said now you could use smaller jugs on the cases if the patterns will bolt up and bore and stroke combos are available.you could always have brad make you a custom crank of the stroke you want.on SW forum there was a thread were a guy weighted his 1200cc watercraft v.s ultra 680.there was only 15lbs difference in the motors weight wise and the 1200 is almost double the displacement.
Interesting. I would have thought the weight difference would be more like 30. Well, if the motor can't me made lighter or smaller than a similar displacement fuji motor not much sense in whipping up a "900".
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Old 03-07-2012, 07:02 PM   #5 (permalink)
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IIRC, weight difference between a smallblock 600 and a BB 700 sled was around 9lbs, all else being equal.

I'm pretty sure it could be done, cutting/welding 2 small block cases into a triple. But would be pretty time consuming and expensive. (I recall 10-12 years ago, there were such motors made from Rotax 670's..?)

So using WC cases is an easier and cheaper solution - and more potential for big HP

(But then, a small block triple, using 660 or 685 jugs, done by e.g Rugland should be a ripper )
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Old 03-07-2012, 08:16 PM   #6 (permalink)
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Quote:
Originally Posted by ivar View Post
IIRC, weight difference between a smallblock 600 and a BB 700 sled was around 9lbs, all else being equal.

I'm pretty sure it could be done, cutting/welding 2 small block cases into a triple. But would be pretty time consuming and expensive. (I recall 10-12 years ago, there were such motors made from Rotax 670's..?)

So using WC cases is an easier and cheaper solution - and more potential for big HP

(But then, a small block triple, using 660 or 685 jugs, done by e.g Rugland should be a ripper )
Hmmm!!
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