Strange bottle on Thorneycroft engine

[kioo]

Can anyone please tell me the purpose of the cylindrical plastic bottle, approx 35X10 cm, connected to, possibly, a crankcase breather by reinforced clear plastic hose. The engine is 6-cyl 200 hp and the bottle is marked "Mercruiser" with a "fill to" line and has a largish steel Hex attached to it`s base. I would also welcome advice on the type of oil to use.

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[omega2]

The bottle is to catch the muck your engine breathing out, and save you the bother of cleaning it from the bilge. Remove the the plastic hose and put your hand onto the breather to stop it, when removed you will hear and feel a gasp of escaping air and possibly oil/water. Not to worry too much replace the pipe and bottle and monitor. Elderly engines do tend to wheeze a bit. If it aint broke don't fix it.

<hr width=100% size=1>J HAMER