Impeller tolerances
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Impeller tolerances

  1. #1
    SLOW MEMBER slowboy's Avatar
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    Default Impeller tolerances

    I just put an AA stainless impeller into my boat. The pump is a dominator. I set the clearance from the trailing edge of the wear ring and the leading edge of the impeller to .025. I noticed when I ran the boat today, that there was some noise coming from the pump.

    What should the wear ring clearance be between the wear ring surface and the impeller? I cant see any visible signs of rubbing anywhere, and the impeller spins free by hand.

    I cut the impeller down from a 9.25 to an AA. Could it be possible that I have to balance this again?

    Thanks for the help, Ryan
    WORK HARDER, MILLIONS ON WELFARE DEPEND ON YOU.
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  3. #2
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    Default Noise

    Is this the first time you have run a ss impeller? Is the noise only at idle? Does the noise go away if you give it a little throttle?
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    SLOW MEMBER slowboy's Avatar
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    This is the first impeller that I have owned that is stainless. I have broken a bunch of aluminum impellers. The noise is only there at idle, it seems to come and go. I cannot hear any noise or vibration when there is some throttle, even at around 1500 rpms. Seems the worst around 1000 rpms.

    Still the noise sounds terriable.

    On a good note, the boat ran 86 tonight at a nice low 5500 rpms.
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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by slowboy View Post
    I just put an AA stainless impeller into my boat. The pump is a dominator. I set the clearance from the trailing edge of the wear ring and the leading edge of the impeller to .025. I noticed when I ran the boat today, that there was some noise coming from the pump.

    What should the wear ring clearance be between the wear ring surface and the impeller? I cant see any visible signs of rubbing anywhere, and the impeller spins free by hand.

    I cut the impeller down from a 9.25 to an AA. Could it be possible that I have to balance this again?

    Thanks for the help, Ryan
    Was the boat in the water? Hopefully not too dumb of a question.

    You should always get a stainless impeller rebalanced after any cutting IMHO.

    I had to remove over 8 grams of weight from mine when I got it....

    A stainless will do funny things at idle, sounds similar to someone knocking on th hull from underneath..

    GT
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    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......
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    SLOW MEMBER slowboy's Avatar
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    Quote Originally Posted by GT Jets View Post
    Was the boat in the water? Hopefully not too dumb of a question.

    You should always get a stainless impeller rebalanced after any cutting IMHO.

    I had to remove over 8 grams of weight from mine when I got it....

    A stainless will do funny things at idle, sounds similar to someone knocking on th hull from underneath..

    GT
    Yeah, I had it in the water before I started it up. I think I will balance it tomorrow just to eliminate that.

    The sounds were not a knocking sound, but more like a metal contact sound. It sure did sound knarley.
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  8. #6
    Senior Member GT Jets's Avatar
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    Quote Originally Posted by slowboy View Post
    Yeah, I had it in the water before I started it up. I think I will balance it tomorrow just to eliminate that.

    The sounds were not a knocking sound, but more like a metal contact sound. It sure did sound knarley.
    Any idea on the condition of the bowl bearings? there could be an issue there too. Grinding noises are never good.

    GT
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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......
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    Default Driveline

    The relationship between your driveline yolk and your impeller shaft has become loose over the years.When you apply throttle the splines lock up to one another and the noise goes away as you return to idle the rattle will return. A lot of times you can turn the idle up intil the noise goes away .If you have to turn the idle up to far in order to get rid of the noise then replacing the driveline yolk and possibly the shaft is in your future. The noise is more agravating than harmful.This is a very common problem.
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    Quote Originally Posted by GT Jets View Post
    Any idea on the condition of the bowl bearings? there could be an issue there too. Grinding noises are never good.

    GT
    I just put a new standard wear ring in last fall, also a new bearing up front as well as the bushings in the bowl. The noise was not there last time I had it out with the aluminum impeller in it. I am positive it has something to do with the impeller.

    I pulled the impeller tonight (thank goodness the pump is set back) and installed the bowl back onto the pump with no impeller in it. I ran the engine, and it made no noises at all.

    I cant see any contact marks on the impeller wear ring surface, or on the wear ring. Maybe I will put a coat of speedcoat spray on everything and go run it again. That should tell me if something is rubbing.
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    Quote Originally Posted by greg shoemaker View Post
    The relationship between your driveline yolk and your impeller shaft has become loose over the years.When you apply throttle the splines lock up to one another and the noise goes away as you return to idle the rattle will return. A lot of times you can turn the idle up intil the noise goes away .If you have to turn the idle up to far in order to get rid of the noise then replacing the driveline yolk and possibly the shaft is in your future. The noise is more agravating than harmful.This is a very common problem.
    Why did it just start after replacing the impeller? Does maybe the weight of the new impeller make a difference on that? It made no noise last week with the aluminum impeller at all.
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  12. #10
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    Some people say that deal GS described is worse when running a heavy impeller like a stainless or Mag Bronze.
    B1Racing.net
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    Quote Originally Posted by slowboy View Post
    I just put a new standard wear ring in last fall, also a new bearing up front as well as the bushings in the bowl. The noise was not there last time I had it out with the aluminum impeller in it. I am positive it has something to do with the impeller.

    I pulled the impeller tonight (thank goodness the pump is set back) and installed the bowl back onto the pump with no impeller in it. I ran the engine, and it made no noises at all.

    I cant see any contact marks on the impeller wear ring surface, or on the wear ring. Maybe I will put a coat of speedcoat spray on everything and go run it again. That should tell me if something is rubbing.
    Another cheat is to put some super high viscosity extreme pressure lube on the pump shaft splines, if it's quiet for a bit then gets noisey, do as the pro says and pick up a new yoke.

    My stainless just rattles at idle (if you can call it an idle), I have a zerk fitting that I occasionally hit with some OMC extreme pressure lube, it stays quiet for about 1 outing then comes back, You get used to it...

    Get louder exhaust.

    GT
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......
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    Quote Originally Posted by GT Jets View Post
    Another cheat is to put some super high viscosity extreme pressure lube on the pump shaft splines, if it's quiet for a bit then gets noisey, do as the pro says and pick up a new yoke.

    My stainless just rattles at idle (if you can call it an idle), I have a zerk fitting that I occasionally hit with some OMC extreme pressure lube, it stays quiet for about 1 outing then comes back, You get used to it...

    Get louder exhaust.

    GT
    I am going to balance the impeller tomorrow, then put it back in as I had it. I will bring my grease gun with me to the lake and grease the yoke splines if it still makes noise. I have a grease fitting on my yoke as well.

    Thanks for all of the help, Ryan
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    I had our local driveshaft shop balance my impeller, and he had to take off lots of material to get it balanced. He used a solid 1.25 inch shaft and said the shaft was running out .050 at 500 rpms because of the inbalanced impeller. He said the runout got better as he sped it up.

    I wonder if at idle the unbalanced impeller was causing runout on my pump shaft, and causing it to rub a little on my wear ring?

    I installed the impeller last night and will take it out today to see if the noise is gone. If not, I am going to look at the driveline next.
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    Quote Originally Posted by slowboy View Post
    Why did it just start after replacing the impeller? Does maybe the weight of the new impeller make a difference on that? It made no noise last week with the aluminum impeller at all.
    Especially if the engine idle has any lope to it, a heavy impeller will tend to even out the pump shaft speed, but, the engine lope will "slam" the splines against one side, then the other, as engine rotational speed changes, if there is enough looseness in the splines.

    A light impeller follows the engine better.

    Once RPM is up, impeller resistance against the pump load keeps the splines locked against one side (also exhaust noise covers it up too).
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