vacuum gauge

[joe_db]

I got a liquid filled vacuum gauge from Fleabay.
I can't decide if I shoudl hook it to the intake manifold or the fuel filter.
Any ideas which would be more useful?

[Flagman101]

What do you wish to monitor?
Vacuum on a fuel line??
Vacuum on the carb sure but its a single carb engine.

[Dave Neptune]

Vacuum gage

Joe, use it to monitor the engine as it is the only gage that is not affected by how dirty the prop or hull are!!! On a constant duty motor I don't know why anybody would be without one!!! It is the first thing I add to any gas powered boat big or small. I use mine to set my cruising LOAD (manifold preassure) and then check the tach to see if all is well with the engine and or the bottom!

Very useful when you understand what it is that they measure.

Dave Neptune

[tenders]

> it is the only gage that is not affected by how dirty the prop or hull are!

I have not noticed my oil pressure, temperature, voltage, or fuel gauges affected by a fouled prop or hull.

[Dave Neptune]

What's it do?

Tenders, very true that those gages aren't affected however they do not measure how hard the engine is working/performing to achieve the same RPM, they only tell you how that part of the engine is working. The tach however will deffinately be affected by RPM's versus the actual load you are putting on the engine which can only be measured by a Vacuum Gage. It is a constant measure of what the engine is requiring (how much it needs from the carb) to achieve the same RPM including the gunk on the prop or hull as well as your "tune" going bad and/or fuel causing problems etc.

I will chime in later with an explanation of what the V/G actually does as I have to get to work soon~~~darn!

I too was a not enlightened until I started working on a dyno testing many types of gas engines.

Dave Neptune

[joe_db]

UPDATE:
I put my vacuum gauge on the fuel filter. The vacuum went up one day until the engine died. Then later it went to 0. Hmmmmm....fuel filters don't unclog themselves.
But fuel tanks do!
Seems there was some crud that would block the pickup and then drop off when you released the vacuum to change filters
I am SO glad I have that gauge
*also took the screen off the pickup. What a place for a filter!

[keelcooler]

I can not seem to find a 0-10 psi fuel pressure gauge. Do I have to go with a 0-15 gauge?

[joe_db]

Update:
I got another Ebay vacuum gauge and put it on the intake side of the Racor. This will make future diagnostics easy. Output gauge goes up = clogged filter. Both gauges go up = clog in tank pickup or clogged vent.
BTW - All the fuel pressure gauges I see on FleaBay are 0-15 (or more) PSI. Make sure and get a liquid filled one or it will be jumping around all the time.