Originally Posted by JimsCAL
The area you have circled is on the the valve cover. Not sure what that little unit is however. Maybe a crankcase breather? If so, they are commonly connected to the air inlet to burn the vapors rather than have them vent to the engine compartment.
You point me in the proper direction with the proper name. Google helped after that.
Earlier M25 engines had the crankcase breather tubes simply directed down below the engine. Later engines re-routed the breather tube to a spot near the air filter, so that the oily fumes are sucked into the engine when it is running. I was planning to do that myself (I have an '87 M25XP), until I talked to a Westerbeke/Universal rep at a boatshow. One of the "problems" with routing the breather hose to a spot near the air filter is that the oil fumes (from the crankcase) tend to get the air filter dirty at a faster rate. Instead, at the suggestion of the W/U rep, I took the intake manifold off, and drilled and tapped a hole for an elbow fitting. To that fitting I attached the other end of the breather tube. Now the oily air is sucked directly into the engine and bypasses the air filter. It has worked very well that way for the past 10 years or so. Others have simply attached their breather tubes to a spot near the air filter, and others have attached fittings to the air filter housing, all with good results.