Like I posted in your other thread, to get a good read on it you should do a pressure test of the R/V cavity. I have heard of the R/V having a slow leaks before, but it's not like it common. How did the guy come to the conclusion that gave it the "look over", or was it just an assumption on his part?
By pinching the supply side that will stop the flow of oil coming from the tank. But on the return side, which there will be oil in, you'll get a back flow from there. So, you technically won't be getting a good result from the test. To get to the R/V return side you can remove the band clamp around the from the main pipe to the cone pipe (there are two Socket head cap screws that hold the cone pipe to the engine case as well) that connects to the water box. With that part of the exhaust it will make it much easier to work on for getting to the return side. If it's your starboard engine there is a bit more room to work with and you might be able to get to it without removing the exhaust cone. In the service manual it will tell you how to do the pressure test of the R/V. If you can hold air pressure then you can hold oil, then you'll need to investigate the oil injection pump, there is a check valve in that which could fail, allowing oil to slowly drip from the oil injection nozzles into the crankcase. I guess a cheater way to check that would be to remove the carbs and look into the carb inlets of the R/V cover and rotate the engine so that the R/V would actually block one of the ports and you could see if oil starts to collect in that inlet versus draining into the crankcase. Either way, it doesn't seem to be leaking all that much. But to troubleshoot it will cost some time and tools.
But, it's not just a seal that you can replace. You'd need a whole new or remanufactured crankshaft. And to do that, you need to remove and tear down the entire engine. And while your in there, you might as well rebuild the engine. So I think it best to some how monitor just how much oil it does leak and if using the pincher will slow it down any. Once you can pinpoint the leak that will determine just how costly the repair is going to cost. Could be expensive, or it could be a $145 dollar oil pump, so you can see how important it is to finding the right defect.
