Volvo MD2020 Flywheel Housing Opening

[AMK Endless Sum]

I have a Volvo MD2020D with sail drive as an auxiliary for a 2001 Bavaria 37 Cruiser. Only 6 months with this boat and still sorting out the diesel. I’m trying to stay ahead of trouble and learn more (engine runs nicely / reliably so far – 1100 hours if meter is correct). I was surprised to find and open treaded 1/2” hole on the right side of the flywheel housing at about halfway up. At first, I was thinking it should be closed with a plug and the housing filled with oil. I can see the threads on the flywheel and not sure about if the housing is supposed to be oil filled and if not why the treaded hole. Any thoughts – ideas?

[DougR]

The hole is there to fit an inductive tach sender in other engine applications, such as genset or other industrial engine application. The flywheel housing is supposed to be dry...no oil.

My recollection is that the engine was supplied with a plastic plug in the hole just to keep stuff out.....screw drivers, finger tips, etc. A piece of duct tape would probably do the job.

[AMK Endless Sum]

Thanks Doug -- I like the answer!

[RaymondR]

The "threads" you can see on the flywheel are the gear teeth the starter motor engages to crank the engine, it wont hurt to spray a bit of lubricant into the hole whilst the engines running occasionally to keep them rust free and lubricated.

[AMK Endless Sum]

Yes -- gear teeth are what I see, not "threads". Thanks for clarifying.