This is a VERY simple system and you can probably fix it.You are reasonably safe prefixing and you can also fill your reservoir manually. The oil tank fills from crankcase pressure on the in the boat main oil tank. The line is filled with crankcase pressure on the right side of the block and th fitting comes out sideways. The line runs into the boat through the loom and pressurizes the oil tank in the boar. That pressure pushed, yes pushes, the oil to the main reservoir on the front of the engine. The upper reservoir provides oil to the gear driven pump, driven by a grey plastic gear inside the engine.The Main issues are: 1. Pressure or oil feed lines become kinked or compressed in the loom loops and are hidden where it enters the engine. 2. Oil tank cap(s) is loose Cracked or stripped on the actual lower tank, preventing pressure from developing.3. Hose fittings are loose or the pressure hose has a small hole in it allowing leakage of pressure from crankcase.4. Laser drilled hole (regulated by hole size) in diaphragm on engine is plugged preventing crankcase pressure from entering air supply hose.5. Trash in oil port necks where fittings are located that restrict flow of trash compromising system.Other unrelated issues are:Oil gear failure which should have a beeper on systems post 1986Oil pump failure which is rareTrash in reservoir neck ports on pump housing or reservoir exit.Hose degradation over aging hosesClabbering of uncompatible oils used. Mixing of dissimilar oils can cause Clabbering, stringy oil clogging systems. There are more though this will give you a good start.
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