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BIG JOHNSON

  • Karma: +1/-0
Vacuum Gauge
« on: March 13, 2012, 08:27:44 PM »
Thinkin on putting in a vac gauge to see what she's pulling. I have a 1/2" vacuum port not being used on my intake manifold and I can make space for a gauge by deleting a fuel gauge and using a three way switch, formerly for the original imco tank selector to monitor either tank by flip of a switch...

My uncle had a '65 Impala with a vacuum gauge disguised as a fuel economy gauge called an economizer. I think I will be saving a lot of fuel to begin with this season by having installed a fuel pres. regulator so my carb isn't being force-fed and flooded out all the time... Sure would be nice to cruise down to Pirate's cove from Laughlin and not have to buy $200 in fuel there.

Anybody ever used one? Good idea? Waste of time and money?

I understand this is a jet boat and I won't let fuel usage control my fun, if I wanna use it I know how to get rid of it.. Just thinkin if on a long cruise if I only have to back off a mile or two per hour i can save fuel if I want.
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  • Boat #1: 1994 Ultra LX 21"
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mobboss

  • Karma: +15/-0
Re: Vacuum Gauge
« Reply #1 on: March 13, 2012, 08:37:54 PM »
if memory serves me correctly the only reason to use a vacuum gauge on an engine is to see that all the cylander are pulling the same. not sure it will help you to watch fuel economy ???   
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GT Jets

  • Karma: +192/-0
Re: Vacuum Gauge
« Reply #2 on: March 13, 2012, 09:04:04 PM »
Big J,

I run vacuum gauges on most of my "crap"...

I don't know about using the term "fuel economy" when the boat has a big squirting appendage in the ass end.... :o

You will be freaked out the first time you run it balls out.....There is little to no vacuum generated at WOT...I use it for several reasons, one of which is to see where I am at as far carburetor size.

The guy that had my boat before me put in two fuel gauges too.... :screwy:  Double pole double throw switch on the selector and viola!  ;)






You said fuel economy....... :o ::) :P ??? ;D      uh huh huh
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  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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Quote from: Brad @ SoCalJetBoats.com on December 22, 2009, 07:40:31 PM
If i get some free time tonight at work, ill play with it and post it for everyone to see.

Quote from: IRRebel on June 11, 2011, 07:30:45 PM
Time to man up and yank it John!  :banghead:
Ray

BIG JOHNSON

  • Karma: +1/-0
Re: Re: Vacuum Gauge
« Reply #3 on: March 13, 2012, 09:20:52 PM »
Quote from: GT Jets on March 13, 2012, 09:04:04 PM
Big J,

I run vacuum gauges on most of my "crap"...

I don't know about using the term "fuel economy" when the boat has a big squirting appendage in the ass end.... :o

You will be freaked out the first time you run it balls out.....There is little to no vacuum generated at WOT...I use it for several reasons, one of which is to see where I am at as far carburetor size.

The guy that had my boat before me put in two fuel gauges too.... :screwy:  Double pole double throw switch on the selector and viola!  ;)






You said fuel economy....... :o ::) :P ??? ;D      uh huh huh

Ha ha ha

Ok so, let's just say I wanna be a miser about fuel economy.. will the readings from a vacuum gauge show me that sweet spot when planed out or just another needle that moves? (That's my question, not asking for approval since.. well.. I'm probably gonna do it anyway because I can.)

Sent from my ADR6400L using Tapatalk
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  • Boat #1: 1994 Ultra LX 21"
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ka0tyk

  • Karma: +30/-0
Re: Vacuum Gauge
« Reply #4 on: March 13, 2012, 09:31:46 PM »
if you take your skirt off when you drive your boat your gauge should always be reading "0"
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BIG JOHNSON

  • Karma: +1/-0
Re: Re: Vacuum Gauge
« Reply #5 on: March 13, 2012, 09:37:33 PM »
Quote from: ka0tyk on March 13, 2012, 09:31:46 PM
if you take your skirt off when you drive your boat your gauge should always be reading "0"
True, not like I drive it to work and back. I always end up going on a long cruise every time I go and I aol never let fuel prices tell me how to drive or how far I can't go... If I see fuel, I top off cause paddling sucks. Probably the information guru part of me just wants to know and calculate.

Sent from my ADR6400L using Tapatalk
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GT Jets

  • Karma: +192/-0
Re: Re: Vacuum Gauge
« Reply #6 on: March 13, 2012, 09:38:12 PM »
Quote from: BIG JOHNSON on March 13, 2012, 09:20:52 PM
Ha ha ha

Ok so, let's just say I wanna be a miser about fuel economy.. will the readings from a vacuum gauge show me that sweet spot when planed out or just another needle that moves? (That's my question, not asking for approval since.. well.. I'm probably gonna do it anyway because I can.)

Sent from my ADR6400L using Tapatalk


Oh absolutely!

The sweet spot will be with the ignition off and the boat on the trailer.... :sly:


In all seriousness...... :D The gauge will drop like an egg out of a plane when the RPM's get above about 3500 PRM and stay quite low while on plane, but there will be some fluctuation between 3,500 and say 5,000 (give or take  ;) ) and the "sweet spot" you speak of will be the highest reading you can achieve, with your carburetor it will be with the secondaries closed, or nearly closed and you will definitely see them open on the needle....

If memory serves (seldom does) I think with an A impeller the primaries will only get you into the low two thousands (2000-2400 RPM) which may compute to just on plane, but in all honesty it has been decades... :o

GT
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  • Boat #1: 1992 Carrera 20.5 Elite (I/O bitches)
  • Boat #2: 19' Bubble deck Jet BBC Berkeley
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Quote from: Brad @ SoCalJetBoats.com on December 22, 2009, 07:40:31 PM
If i get some free time tonight at work, ill play with it and post it for everyone to see.

Quote from: IRRebel on June 11, 2011, 07:30:45 PM
Time to man up and yank it John!  :banghead:
Ray

ka0tyk

  • Karma: +30/-0
Re: Vacuum Gauge
« Reply #7 on: March 13, 2012, 10:33:17 PM »
im just messin with you by the way.   ^-^  post more pix of yer boat.  love the progress so far.
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SoCalPSD

  • Karma: +4/-0
Re: Vacuum Gauge
« Reply #8 on: March 14, 2012, 07:53:34 AM »
Its funny cause my boat came with a vac gauge and couldn't really understand why the hell it was there.

Fat fingered from the phone-  Corey
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Quote from: GT Jets on May 30, 2012, 05:52:07 PM

In my best "grandad" voice with a cigarette hanging out of my mouth....  "if a day goes by and you learn nothing, I hope like hell you got a lot of sleep".... :thumbup:

MPKardell

  • Karma: +1/-0
Re: Vacuum Gauge
« Reply #9 on: March 14, 2012, 03:33:58 PM »
Quote from: GT Jets on March 13, 2012, 09:38:12 PM

Oh absolutely!

The sweet spot will be with the ignition off and the boat on the trailer.... :sly:


In all seriousness...... :D The gauge will drop like an egg out of a plane when the RPM's get above about 3500 PRM and stay quite low while on plane, but there will be some fluctuation between 3,500 and say 5,000 (give or take  ;) ) and the "sweet spot" you speak of will be the highest reading you can achieve, with your carburetor it will be with the secondaries closed, or nearly closed and you will definitely see them open on the needle....

If memory serves (seldom does) I think with an A impeller the primaries will only get you into the low two thousands (2000-2400 RPM) which may compute to just on plane, but in all honesty it has been decades... :o

GT

GT - I'm spinning a 9.25" impeller, and even on my old Q-jet (tiny primaries) I could run up to about 3k before the secondaries started opening.  That's less than 150 HP, and equates to about 30-31 MPH on my 22" day cruiser.

Big Johnson - At the risk of stating the obvious, the key to good fuel economy while cruising is to avoid getting into the secondaries.  My skiing speed takes the RPM's to about 3200, at which point the secondaries have opened slightly.  And my fuel economy sucks big time from there on up.  The added drag from the ski doesn't help either.....

I've got another cruise economy enhancement modification that I'll post about later....

Matt
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  • Boat #1: 1991 Dana 22' day cruiser
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