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Thread: O/B Impeller setup

  1. #1
    Moderator LuJon's Avatar
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    Question O/B Impeller setup

    Curious exactly what goes into setting up an impeller on an outboard. I am under the understanding that there are a bunch of shims that are used to optimize the impellers position within the housing but not much beyond that. I would imagine that you should measure the clearances between the housing and blades and sink the impeller deeper or shallower depending on how worn it is.
    Thanks

  2. #2
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    Default Impeller

    are you talking about a JET drive out board ? or the water pump ?

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    Member Dupont Spinner's Avatar
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    Default

    Shim it till it almost touches the sleeve. Tight, tight but still need to be able to turn over.

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    Moderator LuJon's Avatar
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    Default

    Quote Originally Posted by Sid View Post
    are you talking about a JET drive out board ? or the water pump ?
    Rereading my original post I guess that aint so clear. Yes the Jet drive.

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    Most jets have 8 shims. A new impeller will have 2 or three on the top and 5 or 6 on the bottom of the impeller. You'll always use all the shims but will stack more on top as the impeller and sleeve wear, which pushes the impeller down further into the cone.

    Dick Stallman @ Outboard Jet told me a long time ago to shim until the impeller touches the sleeve and then back it off with two or three shims on the bottom. I found much better performance with closer tolerances. I like to be down to one shim from touching. If you get it to where the impeller is lightly dragging on the sleeve in the driveway the silt in the Su will lock it up tight when you try to start it at the landing, so don't shim it too aggressively. I used to use a half-thickness shim to get things really perfect but don't pay that much attention any more. Heavy loads and the ability to get the load on step will teach you a lot about jet clearance.

  6. #6

    Default Diff. Impellers??

    What performance is there to gain if any, out of a different impeller on a 60h.p. outboard... Don't they make a stainless one or different number or angle of blades?

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    I had a stainless 4 blade impeller on a 200 and it made a very big improvement. I then bought a stainless impeller for a 50 horse and it's not good at all. I can't get the revs up with the stainless so the performance suffers out of the hole and at top end. I have the stainless impeller on the shelf as a back-up use aluminum. I'd like to hear what others have experienced.

  8. #8

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    The only thing I dont like about the SS impeller is that it is a lot stronger than the aluminum sleeve and foot that surrounds it. I had a 140 with a SS impeller and it managed to suck up the perfectly shaped rock to somehow get between the impeller and foot needless to say the impeller won and the foot cracked.

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