Here is a secondary electric pump that comes on when you turn the key on and continues to run until the main engine oil pump satisfies the pressure switch that you plumb into the system. the switch is adjustable and the pump puts out 55psi. Anytime that your oil pressure drops below 60psi (or what ever you have the switch set to) the pump will come on and protect your engine. I had one of these on my engine to prelube before startup and it was on a timer so it would continue to run for three min. to protect my turbos. The only reason I took it off was to shed some weight from the boat. I still bolt it on temporarily to prelube any time the engine sets for any length of time. This pump weighs 3lbs. Also this deal pumps from the drain plug access so when you decide to change the oil just hook a line from the pump to a catch can and it will pump the pan out in a few sec.
And costs $294 , the switch is another $70. If its dependable enough for an airplane it should be fine for a boat.
INFINITY Aerospace: Home Page www.InfinityAerospace.com, Infinity 1, landing gear, stick grips