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Bswieter52

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1973 Silverline Jet Boat Problems
« on: May 26, 2023, 12:23:50 PM »
Hi. New to the forum and jet boats. Bought a 1973 Silverline with a 455 Olds and Berkeley 12JC-A at the beginning of May. Changed the oil and packed the trailer bearings and went to Sterling Revivor in Colorado this past week for its first time on the water since 2019. Have not been able to get much if any info on the boat from the previous owner as he moved to Texas and I bought the boat from his neighbor. Anyway, once on the water there was some pretty clear issues. The engine has its own issues which is a different problem. But the jet had an issue of seeming to lack any push. At 1500 rpm the boat went 5 mph and at  3500 rpm the boat went 9 mph. There was a very bad vibration at anything above 2500 rpm but I'm pretty sure that is coming from the engine. Pretty much all I got out of the previous owner is that the engine is supposed to have less than 50 hrs on it and he sent the jet to a place in California called CP Performance to get rebuilt. I do not know when the engine was rebuilt or when the jet was sent off. I did meet a very knowledge guy by the name of Zoomin Newman at the boat ramp with a jet boat and asked him some simple questions. He gave a very helpful jet drive 101 explanation and recommended this forum if I ran into any problems. Any information on things that might be wrong or good things to know would be very helpful. Thanks
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76Mantra455

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Re: 1973 Silverline Jet Boat Problems
« Reply #1 on: May 27, 2023, 03:52:16 PM »
Check to see if you have anything stuck in the impeller.., pull the hand hole cover off and see what you can find. If there are rocks or debris stuck in there you will not go very fast and have the vibration you are talking about


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Bswieter52

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Re: 1973 Silverline Jet Boat Problems
« Reply #2 on: May 28, 2023, 08:48:38 AM »
Have pulled that cover already. Also looked through the intake in the bottom of the boat and everything is super clean. No debris.

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Re: 1973 Silverline Jet Boat Problems
« Reply #3 on: May 28, 2023, 07:26:36 PM »
As 76Manra455 said, something else is in the pump. Next thing is to pull the bowl off. The trailing edges of the impeller could be trashed, or even have a rock wedged in the impeller or bowl.

Pretty simple to get the bowl off, and if you find nothing in the pump, it's at least peace of mind that everything is ok.

Olds are not the best at oiling, if everything is still factory stock. I hope you don't have to get into the motor to find the vibration.
With the speeds vs rpm, it's most definitely in the pump.

Just my $0.02

Dan'l
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Bswieter52

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Re: 1973 Silverline Jet Boat Problems
« Reply #4 on: May 28, 2023, 08:53:37 PM »
Okay, will pull the pump apart and take a look when I get back in town. Thank you for your $0.02, its very helpful.

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Bswieter52

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Re: 1973 Silverline Jet Boat Problems
« Reply #5 on: June 23, 2023, 06:52:05 PM »
Finally got around to taking it apart today. Everything looks fine. Here is pictures of the boat and the jet.
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Bswieter52

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Re: 1973 Silverline Jet Boat Problems
« Reply #6 on: June 23, 2023, 07:30:24 PM »
As a refresher, the problem is the jet drive lacking any drive.

If you go wide open throttle from a stand still the engine seems to "free rev" to the rev limiter.
If you slowly open the throttle the boat will go about 5 mph at 1500 rpm and 9 mph at 3500 rpm, then the rpms just runaway any higher than that.
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76Mantra455

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1973 Silverline Jet Boat Problems
« Reply #7 on: June 23, 2023, 10:16:38 PM »
Looks like you need a new wear ring you should not be able to look right thru it and see the other side? unless that is the wear ring


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Bswieter52

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Re: 1973 Silverline Jet Boat Problems
« Reply #8 on: June 24, 2023, 10:22:43 AM »
That is the wear ring. It is very shiny.

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76Mantra455

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Re: 1973 Silverline Jet Boat Problems
« Reply #9 on: June 24, 2023, 04:52:06 PM »
Ok well then there has to be a problem with the clearance or impeller.., unless the tach is way off


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Re: 1973 Silverline Jet Boat Problems
« Reply #10 on: June 24, 2023, 05:01:19 PM »
I'd check the radial clearance.
It should be .012 inch per side or so, about .025 total.
I checked at 3 and 9 o'clock.
I've measured .035 inch per side on a sloppy pump.
A properly fitted wear ring fixed the problem.

Dan'l
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Bswieter52

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Re: 1973 Silverline Jet Boat Problems
« Reply #11 on: June 26, 2023, 04:57:47 PM »
How do I measure that radial clearance? I don't think there is a way to get a feeler gauge down by the wear ring. Do I use a dial indicator on the impeller?

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Re: 1973 Silverline Jet Boat Problems
« Reply #12 on: June 27, 2023, 06:17:01 AM »
From the front side.

Dan'l
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Bswieter52

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Re: 1973 Silverline Jet Boat Problems
« Reply #13 on: June 30, 2023, 07:34:09 PM »
Pulled the jet out of the boat today so I could measure the clearance and found another whole set of issues. I don't think the guy I bought the boat from had a clue what he was doing.

The slip yoke double cardan joint whatever ya call it, was ceased to the pump shaft. Had to use the biggest slide hammer we had to get the pump disconnected from the engine. After we got it off the splines looked super beat up and it looks like it was hammered into place.

I think this is what was causing the vibration. I think they got it hammered on just far enough to force the bolts into place. When you don't allow a double cardan joint to have freedom to slide on a shaft it gets pushed to the side or misaligned causing an out of valence causing a vibration.

Do you guys think my diagnosis is correct? And what is the best way to restore the splines on the pump and the joint to get them functional again?

It took so long to get the pump out I ran out of time to measure the clearance.

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Re: 1973 Silverline Jet Boat Problems
« Reply #14 on: July 07, 2023, 06:27:59 PM »
Could the splines be twisted? That would cause the interference fit and the vibration issues.

A new or good used shaft should be easy to source.

Dan'l

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