Re: What is this?
Just as an FYI, in case you're interested. I've purchased 3 used engines over the past decade or so and always have similar type of questions. I've found it very valuable to get an "owner's manual" (as opposed to a service manual -also a good idea). They explain everything the normal owner needs to know about the engine, routine maintenance, etc. For older OMC manuals that aren't available through BRP.com, you can find them through Kencook.com