Hose line from crankcase on 90hp Merc

[Wisconsin Mike]

Trying to identify the cracked hoselines purpose, can find no reference to this in the shop manual. This is a 1981, inline 6, 90 hp. The hose looks to be connected to possibly a check valve to the crankcase portion of the power head. The hose runs down behind the CDI packs and I think reappears below at the bottom cylinder where it connects again to that cylinder. If it connects to the other cylinders behind the CD packs, I don’t know. See photo included. While the engine runs fair, it is challenging to start and runs a little rough. I’m wondering if this cracked hose line could be contributing to running smoothly.

 

[racerone]

It is called a recirculation oil line.----Oil works it way to the bottom of the engine.----It is then pumped to a fitting near the top bearing.----Find the fittings.----Install a new hose.---Do not run motor without it.

 

[Chris1956]

On the recirculation hose, generally the lower fitting is one way, and the upper fitting is open both ways. You might remove and clean both of them. Oil will tend to pool in the bottom of the crankcase. The crankcase compression and 1 way valve force it to the upper main bearing for lubrication purposes.

You also have balance hoses that connect the reed blocks together. They are 3/8" hoses, and are partially hidden by the carbs and other stuff.