912 100 HP Low oil Pressure under power

Does it behave normally before it gets Hot?

What are you using for a DISPLAY?

Analog or Digital?

What Aircraft?

This may seem like a silly question but... how is your oil level before start-up?

Thanks for your replies,    The plane is CH701,  MGL Stratus Gauge .    Oil level is right at the full mark after burping.  

If it's not a problem with your sensor or wiring it could be a collapsing oil line on the suction side. If the line is collapsing some have inserted a coil spring inside of hose or Peagasus Racing has teflon oil hose all sizes are rated to 30 in-Hg vacuum service up to 130°C (266°F). Temperature range -45°C to 170°C (-49°F to 338°F).

https://www.pegasusautoracing.com/productselection.asp?Product=3490

Install a direct reading pressure gauge fed by braided steel lines and never again wonder what the real oil pressure is.