Author Topic: JETS  (Read 2165 times)

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Offline TylerCV19

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JETS
« on: December 20, 2019, 07:38:24 PM »
Wanted to make a G/C Jet boat thread. Anybody running an overflow dump for pressure concerns or in the stock form is it even unnecessary? Also, thermostats? My jet read off the charts hot this summer (on the gauge) drained and flushed block but can not seem to find the gremlin. Even with a temp gun, nothing really concerned me, manifold elbows ran the warmest around 220 after some WOT passes. Also, anybody have an impeller for a 12JE, I am only getting 57 out of my 460 and there is a cvx 20 I’ve been in that’s running 70 with the same set up I just don’t have the MSD kit.

Cheers, happy holidays.
“Miss Behavin”
76 CV-19SS 460 Jet

Offline Jason

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  • 1974 CV16SS, 1986 CV23
Re: JETS
« Reply #1 on: December 20, 2019, 08:49:41 PM »
When you flushed the block did you remove the frost plugs? I don't really see any other way to get all the sand out and these jets can suck up a lot.
Jason S.
1974 Glastron Carlson CV16SS 140 I/O
1986 Glastron Carlson CV23 260 I/O

Offline Carlson_from_Germany

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JETS
« Reply #2 on: December 20, 2019, 09:00:58 PM »
No stock CVX20 runs 70mph.
57mph sounds like a good digit.

Offline cv-19

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Re: JETS
« Reply #3 on: December 21, 2019, 12:57:04 PM »

 60 is about top speed on a stock 20 . You don't need the water dump on a stock jet boat.
 
  You should be running in the 145-160 degree range . Do you have the factory tstat system with
  the bypass? This is the only system you should use a tstat. If it has valve in the water supply line
   off the pump it should be full open . If you are using a tstat try running it without it to test. My
  Nephews 23 with a 460 had plugged up at the water inlet lines on the front water pump cover plate
  from corrosion . You can pressure test the motor also if you need to rule out a head gasket problem.

Offline TylerCV19

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Re: JETS
« Reply #4 on: December 24, 2019, 11:52:38 PM »
I promise you this stock cvx 20 is running 70. I will take a video when we summarize it and test drive. I took out the valve to try and rule out a blockage issue. (Dangerous in case of leaks I know) I will definitely check the inlet hoses for corrosion, they seem new but the guy I bought it from was kind of a hack. The thermostat T has never been pulled apart so I’m wondering if there is a foreign thermostat put in place, I appreciate the info. And glad to know I don’t need a pressure relief dump on the stocker set up. I’m running a 750 vac secondary and it’s choking on the top, hopefully it’s just an air intake issue with the dog house that seems to lock everything in.
“Miss Behavin”
76 CV-19SS 460 Jet

Offline TylerCV19

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Re: JETS
« Reply #5 on: December 25, 2019, 12:00:01 AM »
I did not remove the freeze plugs. That is a good idea! Thank you guys, very excited to see you guys this upcoming year with a reliable running CV-19
“Miss Behavin”
76 CV-19SS 460 Jet

Offline Plugcheck

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Re: JETS
« Reply #6 on: December 25, 2019, 07:59:12 AM »
The 460 should operate well with a 750 cfm carb, unless you're pulling above 6500 rpm, which I certainly hope you are not.   Might be an issue if airflow around the air cleaner is restricted.   I assume by a dump or bypass valve you are considering restricting the water pressure from the pump?  Since there commonly is no thermostat in this application, some folks add a valve and calibrate it to temperature results on the engine.   My friend Tim's 23 acts like it could use more cooling, not less, so we leave the valve open.   
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline cv-19

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Re: JETS
« Reply #7 on: December 26, 2019, 09:15:58 AM »

 Your speed is about right for a CV-19. Mine when new with the 455 Olds  ran 58 at 4700 RPM
 The 460 has the same horse power and is a little heavier .If you think the engine
 cover is cutting off air prop it up some and test it or remove it and see. Mine has only 1/4 in.
 between the hatch and top of air cleaner and doesn't cause a problem.

Online Hyperacme

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Re: JETS
« Reply #8 on: December 26, 2019, 09:51:22 AM »
Long time ago and can't find pictures .. But Jason removed Brian's engine to replace rusted frost plugs and used some wire to dig out sand that was packed in the block. He had a small plastic kids pool under it to catch water and sand.
There was quite a bit of sand in bottom of pool when he was done.