Hello, I'm looking at possibly buying a older Chris Craft with 305 engines, the one engine though running well, with normal oil pressure is, is producing a slight oily Sheen behind the engine. It did not stop even when the engines were warm. It is very minor, but noticeably different than the other side. Is this something that is likely to be an easy fix like carburetor or spark plugs, or is this an indicator of a bigger problem? There are not a lot of hours on the engine, less than 350 hours. They seem to run great, start easily, not much smoke. I appreciate the advice!