Most interesting, Dale.
I've a dual Racor
with a vacuum gauge on Led Myne. And I've had single
Racor filters on previous boats.
I note that Racor has given me, both by e-mail and by phone
, excellent customer service
. So an e-mail (to firstname.lastname@example.org
) should work
My reading of what you've written suggests the vent lets you zero the gauge to suit your conditions (you could be on a high altitude lake, a low altitude lake, or at sea level in between). If that's the case, then seems to me that you open the vent to zero the gauge and then close it because you've established zero for your atmospheric conditions.
RacorTech should answer you fast and more reliably than me.
I will note another issue: Racor vacuum gauges (without a vent) are unreliable if they're in a situation where fuel
is supplied to them under pressure (by a pump) and especially if the pump
pressure varies. The gauges are vacuum gauges, measuring any "vacuum" created by clogging of the filter element. If the fuel
is supplied under pressure, especially varying pressure, that defeats a lot of the thinking behind a vacuum gauge. But I have trouble thinking that the vented gauge was designed for that situation.