Installation Manual



 DM-15V Vacuum Gauge Instructions

   0 to -15 inches of Hg (0 to -50 kPa)  

The Dent Marine heavy duty vacuum gauge is intended for use on marine diesel engine systems with in-line primary fuel filters.

Monitoring the health of the fuel filters is critical to proper operation of diesel engines. Clogging of the fuel filters can lead to reduced fuel flow to the diesel engine resulting in fuel starvation problems, rough running, reduced maximum rpm and other problems.


The Dent Marine vacuum gauge is specifically designed for the requirements of the marine diesel engine market. The vacuum gauge includes a black pointer for the instantaneous vacuum reading and a resettable red pointer that shows the highest vacuum achieved. The range of the Dent Marine vacuum gauge more accurately reflects the true requirements of the marine diesel engine by showing the caution area as between -5 and -8 in. Hg and the desired filter replacement at -8 in Hg.1


INSTALLATION:  The gauge is intended for use on the engine (suction) side of the primary fuel filter and may be a new installation or replacement of an existing gauge. The connection is a standard ¼” NPT male fitting. Use a small bead of compatible thread sealer (Leak Lock® works well) on the gauge threads being careful not to get any sealer in the pressure sensing hole. Tighten until snug using a 9/16” wrench (14 mm) on the wrench flats of the gauge. Do not use the gauge body to tighten. Do not over-tighten. Check for leaks. Remove the ATTENTION sticker.


USE:  The top of the gauge has a yellow vent handle. Move the yellow handle to the left (as you face the gauge) to the open position to equalize the internal gauge pressure and zero the black needle. The vent may be left in the open position in normal use.

Next, reset the movable pointer by twisting the center knurled knob clock-wise until the pointer is resting on the 0 peg. That’s it!


CHANGING FUEL FILTERS:  Fuel filter condition can only be ascertained by a vacuum gauge when the engine has been operated under load at wide open throttle (WOT). A well designed primary filtration system with clean filters should not have more than -5 in. Hg (-17 kPa) of vacuum when the engine is running at WOT. As the filter begins to plug the vacuum will rise. By the time the vacuum reaches into the yellow band, -5 to -8” Hg (-17 to -27 kPa) at WOT, the filter should be changed or monitored closely. At -8” Hg   (-27 kPa) the filter should be changed to avoid air bubbles in the fuel, reduced performance or possible damage to the engine1.

1Per “Lugger” Bob Senter of Northern Lights, Inc. Check your engine manual to determine maximum recommended vacuum before fuel filter replacement.