My starboard (Volvo Penta D1-30) engine has developed an oil leak that I need to track down.

My plan of attack is to thoroughly clean the bilge then degrease everything before trying to track down the leak working top down, i.e., identifying the highest part on the engine that is oily. I figure if it's leaking at the top it will incriminate the crankcase ventilation valve, whereas if it leaking lower down it something else, such as the oil pressure sender, and if it leaking at the bottom it's probably the oil pan gaskets or the oil pan itself.

Does anyone have any other tips for tracking down oil leaks?