A typical lawnmower engine (riding) normally does not have an oil pressure gauge installed.  I installed an oil pressure gauge on my MDT (Huskee) SLT 4200, Briggs and Stratton (31P700 series) engine.  The engine came with a port that allowed me to tap oil pressure near the oil filter. 

      These first two photos show the brass coupling and 'plastic' oil pressure line that are connected into the oil pressure port.  On this particular engine, there was a squared plug that had to be removed via wrench.  I then screwed in the brass couplings and oil pressure line into this port.    

   Here is another view of the brass coupling and oil pressure line.

  I did not cut any of the oil pressure line for various reasons.  I didn't want to cut it too short and then not be able to mount the gauge in another location.  I left the excess oil pressure line curled up and then tie-wrapped it to the frame of the riding mower.

        I then continued along the frame of the riding mower.  I followed the wiring harness, but I did not place the oil pressure line into the wiring harness.  I wanted it visible for maintenance purposes.  I did not hook up the light from the oil pressure gauge.  I very rarely use the lights on the riding mower and didn't want the extra hassle of a light for the gauge.

       This photo shows the mounting position of the gauge.  I didn't install the gauge inside the dashboard.  This particular mower does not have much of a dashboard.  I mounted the gauge on the 'steering wheel pedestal'  Granted, everything is exposed and normal care should taken to avoid the oil pressure line and gauge.  Even with normal operation, my left foot does not contact the gauge or the oil pressure line. 

       This is how the gauge looks from the driver's seat.  This may look awkward, but my left foot does not contact the oil pressure gauge or the connection.

When I first start the engine, I get about 60 psig.  As the engine and oil warm up, 40 psig is the running indication.  At a warm idle, 20 to 25 psig is what I read.  These numbers are for a B&S 31P700 series engine with SAE 30w (straight) oil during an average summer day (70 to 80 degree).  The intent isn't to brag about oil pressure, but to get a baseline of the pressures on the engine.  If the engine's oil pressure indicates anything that hasn't been normal, I can easily investigate the problem.  As time goes on, I expect the oil pressure to drop because of engine wear and tear.  I also expect to see variations in oil pressure between fresh and old oil. 

Overall, the installation took about 40 minutes.  I've used this oil pressure gauge all summer (2007) with no problems.  I tried this and really enjoyed the outcome of this particular installation.