Hello guys and gals. I have a 1cyl air-cooled diesel engine in my boat. I want to add an oil cooler to it to help keep it cool as it's fairly closed in and forced ventilation might not be enough. I have the drain plug to pull the oil from but i am looking for where i can safely let the oil back into the engine.

The engine is a generic Chinese diesel in a package similar to the predator box engines often seen on YouTube.

As it doesn't have an oil pump of its own according to the import dealer i have thought about having the oil go in from the rocker arm cover . Would this be more effective than just dumping it back in the oil filling hole ?