Justaplain,
If it is the oil pressure, as others are suggesting, it is a very serious problem. I wouldn't run it much further until you know for sure.
Here is what my boat repair book says about this condition:
It could be due to:
1) Lack of oil.
2) Low oil viscosity.
3) Overheating -- lowering the viscosity.
4) Oil being diluted by fuel contamination.
5) Worn bearings.
6) Oil pressure relieve valves venting oil directly back to sump resulting in a loss of pressure.
7) Oil pumps rarly give out if the oil and filter have been changed regularly.
Please keep me informed as to the diagnosis. I have similar problem with my boat.
Buck