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78millerjet

  • Karma: +0/-0
More jet boat speed
« on: February 17, 2016, 01:52:24 PM »
Im new to the forums and a noob on engine mods. I have a 78 miller 20 ft mini cruiser with the bone stock 460 with log manifilfst. I believe top speed is 54 @ 4400rmp. She's a well built full stringer boat and a bit heavy. Besides an intake manifold electronic ignition speed grate and diverter, what will she need to reach 70? .I would be happy with an honest 65. Thx!
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tamsone6

  • Karma: +7/-0
Re: More jet boat speed
« Reply #1 on: February 17, 2016, 02:10:03 PM »
More hp :) is the pump good?


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FordLover

  • Karma: +72/-0
Re: More jet boat speed
« Reply #2 on: February 17, 2016, 02:11:45 PM »
Enjoy it as a cruiser. That is what she was made for. It wouldn't be money well spent trying to get there. If you want to go 70+ get a smaller boat with more ponies. Better bang for the buck.
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FordLover

  • Karma: +72/-0
Re: More jet boat speed
« Reply #3 on: February 17, 2016, 02:13:27 PM »
More hp :) is the pump good?


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Dont give him false hopes. Lol
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tamsone6

  • Karma: +7/-0
Re: More jet boat speed
« Reply #4 on: February 17, 2016, 02:17:24 PM »

Dont give him false hopes. Lol

Oh yeah that's right, my "400" hp boat will only go about 30 haha

Fordlover is right though, cruisers are best as just that.


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78millerjet

  • Karma: +0/-0
Re: More jet boat speed
« Reply #5 on: February 17, 2016, 02:25:29 PM »
Pump is good. I believe its an A impeller. Sounds like 10 mph is unrealistic for 2k? Its a 9 out of 10 cosmetically and she's a keeper. If I cant get her to 65 ill leave her stock
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tamsone6

  • Karma: +7/-0
Re: More jet boat speed
« Reply #6 on: February 17, 2016, 02:27:05 PM »
What heads, cam, and manifold is it running or are you planning on running?


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78millerjet

  • Karma: +0/-0
Re: More jet boat speed
« Reply #7 on: February 17, 2016, 02:30:27 PM »
Thanks for the replies!
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FordLover

  • Karma: +72/-0
Re: More jet boat speed
« Reply #8 on: February 17, 2016, 02:33:47 PM »
We are happy to help! The real pros will respond soon.
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FordLover

  • Karma: +72/-0
Re: More jet boat speed
« Reply #9 on: February 17, 2016, 02:34:10 PM »
And post some pics. We like pics
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78millerjet

  • Karma: +0/-0
Re: More jet boat speed
« Reply #10 on: February 17, 2016, 02:39:22 PM »
Its bone stock.. was thinking aftermarket intake manifold electronic ignition  speed grate and diverter would wake her up a bit. About the only thing I do know about jets is it takes alot of hp to go fast
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tamsone6

  • Karma: +7/-0
Re: More jet boat speed
« Reply #11 on: February 17, 2016, 02:55:26 PM »
The torker manifold is a good one, so is the stealth... If it doesn't have dove-c heads, worked on d3's or aftermarket heads you're really leaving a lot of power behind.

You'll get a good amount of power out of just a manifold and heads upgrade. Without a set of good breathing heads the other mods won't do as much.


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FordLover

  • Karma: +72/-0
Re: More jet boat speed
« Reply #12 on: February 17, 2016, 03:05:05 PM »
The torker manifold is a good one, so is the stealth... If it doesn't have dove-c heads, worked on d3's or aftermarket heads you're really leaving a lot of power behind.

You'll get a good amount of power out of just a manifold and heads upgrade. Without a set of good breathing heads the other mods won't do as much.


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So our intakes are just for looks? I knew it! Shit!
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78millerjet

  • Karma: +0/-0
Re: More jet boat speed
« Reply #13 on: February 17, 2016, 04:58:27 PM »
Its never been apart...I'm sure its a cast 1978 engineering special. Still has points and stock quad carb. Berkeley jet has never been rebuilt either. Its a great custom boat, ill never part with her even for a younger model...
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FordLover

  • Karma: +72/-0
Re: More jet boat speed
« Reply #14 on: February 17, 2016, 05:01:55 PM »
Pictures?
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GT Jets

  • Karma: +192/-0
Re: More jet boat speed
« Reply #15 on: February 17, 2016, 06:13:23 PM »
From mid 50's 70mph is virtually double the horsepower.  So if you're making in the low to mid 300hp range now,  it will take near 700 ponies to hit your goal.

Be a lot cheaper and less grief to lower your standards.

JMO

GT
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

More2LifeThanMPG

  • Karma: +13/-0
More jet boat speed
« Reply #16 on: February 17, 2016, 06:56:23 PM »
From mid 50's 70mph is virtually double the horsepower.  So if you're making in the low to mid 300hp range now,  it will take near 700 ponies to hit your goal.

Be a lot cheaper and less grief to lower your standards.

JMO

GT

That's what's I kept telling my girlfriend about me... Well now fiancé! Winner!


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  • Boat #1: 1989 Howard 21' River Cruiser
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GT Jets

  • Karma: +192/-0
Re: More jet boat speed
« Reply #17 on: February 17, 2016, 07:02:28 PM »
That's what's I kept telling my girlfriend about me... Well now fiancé! Winner!


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Stick with what works brother.

;D
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

78millerjet

  • Karma: +0/-0
Re: More jet boat speed
« Reply #18 on: February 17, 2016, 08:18:02 PM »
Thanks for all the advice guys!
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FordLover

  • Karma: +72/-0
Re: More jet boat speed
« Reply #19 on: February 17, 2016, 08:19:59 PM »
From mid 50's 70mph is virtually double the horsepower.  So if you're making in the low to mid 300hp range now,  it will take near 700 ponies to hit your goal.

Be a lot cheaper and less grief to lower your standards.

JMO

GT

Tamsone6 doesnt want to hear that!
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GT Jets

  • Karma: +192/-0
Re: More jet boat speed
« Reply #20 on: February 17, 2016, 08:48:07 PM »
Its bone stock.. was thinking aftermarket intake manifold electronic ignition  speed grate and diverter would wake her up a bit. About the only thing I do know about jets is it takes alot of hp to go fast

This is all a really good start,  if you shoot for 60mph, I think you will be happier.

The Place Diverter is an automatic 2-3 mph. The ignition upgrade and intake manifold will make it run a little better but I would call it virtually immeasurable speed gains.

A loader grate could be helpful if set up properly.

A bigger part power gain would be found in a camshaft and carburetor swap. This has to be thought out too, the compression ratio and exhaust system needs to be kept in mind when selecting both.

Still stick by my story of needing to double the power to even graze 70 for a few seconds.

$2000, that will get you to 60mph,  likely not a whisker more.

JMHO, don't shoot the messenger.

GT

  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

GT Jets

  • Karma: +192/-0
Re: More jet boat speed
« Reply #21 on: February 17, 2016, 08:51:09 PM »
Fat fingers. Sorry
« Last Edit: February 17, 2016, 10:06:29 PM by GT Jets »
  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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If i get some free time tonight at work, ill play with it and post it for everyone to see.

Time to man up and yank it John!  :banghead:
Ray

78millerjet

  • Karma: +0/-0
Re: More jet boat speed
« Reply #22 on: February 17, 2016, 08:55:09 PM »
Would the torker manifold and msd ignition do anything thing over stock? Figured if she breathes better maybe a bit better fuel economy.. if its best to just leave her stock. I'm ok with that too
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78millerjet

  • Karma: +0/-0
Re: More jet boat speed
« Reply #23 on: February 17, 2016, 09:00:12 PM »
Sorry GT, didn't see your previous response..thx!
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Flusher

  • Karma: +84/-0
Re: More jet boat speed
« Reply #24 on: February 17, 2016, 09:32:22 PM »
Consider aftermarket aluminum heads.  The right set will will bump your compression and breathing ability while lowering weight.  You really need to find out what your current compression ratio is.

I'm curious why you are only getting 4400 RPM.

I don't see an intake swap making any positive gain.
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"I want to roll with my brother Joe" - Joe Bateman - January 29, 1950 ~ November 27, 2013

 


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