[Question] Dominator 12 s packing adjustment.
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Dominator 12 s packing adjustment.

  1. #1
    Member oldseddie's Avatar
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    Default Dominator 12 s packing adjustment.

    I rebuilt my pump last winter and installed a new stainless impeller and inducer. I tightened the packing while on the bench to where a slight drag was felt while turning the shaft. On first start up I went to adjust the packing but noticed no drip whatsoever. The boat pulled hard out of the hole for the first few trips to the lake. Time before last as I was heading back to the ramp I noticed it was "slipping" on take off with a higher than normal rpm at wot. when I looked at it at home I noticed signs of leakage from the packing. I had read that a loose packing will introduce air and cause slippage. On my next trip to the lake I tightened the Packing a quarter turn per side even though I observed no leak from the packing. The pump once more pulled hard and the wot rpm was back to normal. I still observed a good many bubbles in the jet exhaust. I should mention this boat is an aluminum bass boat built by shoal runner boats. It sits in the water at rest with 1/3 of the bowl out of the water so the shaft is barely submerged. Most of the Jet boats I have seen including the ones my Dad has owned have the bowl mostly submerged. I would tighten the packing further but the shaft that was in the pump had been scored from overtightening or lack of lubrication (water). Should I tighten the packing further until the bubbles are reduced on the pump output or leave it as is until it starts slipping again? I sure don't want to hurt the new AQ shaft as they are quite proud of them.

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  3. #2
    Member oldseddie's Avatar
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    Bump time. I know one of you guys has run into this.

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    Senior Member TexasJet's Avatar
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    Give Greg Shoemaker a call. He has a tech section on this forum.

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    Senior Member jetboatperformance's Avatar
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    regarding the "bubbles in the exaust" you describe , not sure I have ever observed this or what it might be, honestly the shere turbulance of the engine and jet will cause a blender effect , however the shaft rope packings need to fit snugly against the pump shaft sealing surface to seal the shaft from atmosphere so they dont allow air to be drawn to suction process, the packing adjustment should be tight enough allow a very tiny static drip or "leak" so that water will cool and help lubricate the packings , overtightening will cause them and the shaft to run hot , burnish and wear excessivley

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    Member oldseddie's Avatar
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    Thanks Tom. That's my understanding of it but mine doesn't drip at idle. It still blows a significant amount of bubbles at idle speed in forward. I'm sure that the intake is sealed to the pump good so if it's air ingestion and not bowl or impellor turbulence, it would have to be the rope seal. My boat has an engine hatch (rear fishing deck) so I can't observe what is going on much above idle. I may try to rig a gopro and flashlight so I can investigate it further as it doesn't seem to have the bite it had when I first rebuilt it and it did respond well to tightening the packing a small amount.




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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by oldseddie View Post
    Thanks Tom. That's my understanding of it but mine doesn't drip at idle. It still blows a significant amount of bubbles at idle speed in forward. I'm sure that the intake is sealed to the pump good so if it's air ingestion and not bowl or impellor turbulence, it would have to be the rope seal. My boat has an engine hatch (rear fishing deck) so I can't observe what is going on much above idle. I may try to rig a gopro and flashlight so I can investigate it further as it doesn't seem to have the bite it had when I first rebuilt it and it did respond well to tightening the packing a small amount.




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    Sorry to be stubborn but Bubbles ? from where ?

  9. #7
    Member oldseddie's Avatar
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    The water squirting out the nozzle.




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    Last edited by oldseddie; 07-12-2016 at 05:08 PM.

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    Senior Member jetboatperformance's Avatar
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    OK I'll have to "give" I will admit I have never spent much time or thought on the ariation (sp) of the water on the jet exit ,(relative to your shaft packings ) likley as not if your shaft packings are not leaking a significant amount to atmosphere they are probably doing thier job of sealing the suction process from atmosphere as well

  11. #9
    Member oldseddie's Avatar
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    I had the boat on the lake today and it seemed to me that the bite was back and so was the fuel economy. The bubbles in the pump output didn't appear excessive so I guess my adjustment did the trick.

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  12. #10
    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by oldseddie View Post
    I had the boat on the lake today and it seemed to me that the bite was back and so was the fuel economy. The bubbles in the pump output didn't appear excessive so I guess my adjustment did the trick.

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    Good Luck glad itworked out , head nhome to watch the bubbles in a Silver Bullet my self

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