How to read a vacuum gauge (and why you want one today!)

lowkee

Lieutenant Commander
Joined
Dec 13, 2008
Messages
1,890
This is both a boat and non-boat topic, so I figured I'd play it safe and post it here.

Having recently gotten myself a boat, I wanted to learn some tricks of automotive mechanics, seeing as my IO is a GM 3.0L, which is pretty much a car engine.

A site I found very helpful is this. It is meant for classic car rebuilding, but has some nice general engine tutorials, one of them being 'How to read a vacuum gauge' and boy is it helpful!

I recently remove my distributor and had to reset the timing when it was reinstalled and using my shiny new vacuum gauge I was able to adjust the timing to 'close enough' until I rent a timing light.

Here is a quick excerpt from the site:

"A vacuum gauge can tell as much about the internal and external workings of an engine as the combination of a voltmeter, compression gauge, stethoscope and timing light. Really!

Note also that most vacuum gauges are equipped with an additional scale that measures fuel pump pressure. This allows the user to connect the hose directly to the fuel line entering the carburetor to measure the fuel pump's pressure. Since many fuel system problems can be traced to the pumps themselves, such a tool can save a lot of troubleshooting time."

Check it out, as it has a really nifty animation for each scenario, which teaches you how to read one *much* better than any description can do.

If you don't have a vacuum gauge, Harbor Freight has a really nice one for $15.

All in all, I'm really glad I found that site, as that's a lot of info coming from just one gauge, and the 3.0 manifold even has a port made specifically for it! Sweet!
 

lowkee

Lieutenant Commander
Joined
Dec 13, 2008
Messages
1,890
Re: How to read a vacuum gauge (and why you want one today!)

Doh! Well, at least you know it's a good tutorial when..
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
Joined
May 19, 2001
Messages
26,066
Re: How to read a vacuum gauge (and why you want one today!)

Good to know stuff.

I like the mercury ones for multiple carbs on a motorcycle to get them adjusted properly.

If you install an oil pressure gauge many people do not know how to read those either :eek:
 

puddle jumper

Captain
Joined
Jul 5, 2006
Messages
3,830
Re: How to read a vacuum gauge (and why you want one today!)

Vacuum gauges can also be used as a low teck insterment for fuel millage on gas engines.
 
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