New gearbox - how soon to change oil.

[Mataji]

Just had a new gearbox fitted to my 21hp Nanni. After how many hours should I change the gearbox oil?

 

[VicS]

After 30 hours is typical Then every 500 hrs or at least every year.
Personally I'd only inspect the condition of the oil on the dipstick after the first change and only change it if/when it is no longer "clear and bright".
More vigilance obviously if water cooled.

 

[Boater Sam]

If its a Hurth/ZF, every week if you want it to last.
If its a PRM, once a decade.

 

[Tamar]

If its a Hurth/ZF, every week if you want it to last.
If its a PRM, once a decade.

Unfair. My zf5 has done around 15000 hours and still going strong. I change the oil every 250 hrs, same as the engine oil.

 

[greeny]

This is a genuine question and I'm not trying to be smart and undermine the knowledge of far more experienced people on here. I'm Interested to know why gearbox oil should be changed so often as is being recommended here. Engine oil yes, with all the possible contamination issues but surely gearbox oil is isolated from any contamination. From new, maybe an initial change after a short period to remove any initial bits after run in but then why not follow the manual's recommendations. I know marine gearboxes are a different animal to car boxes but does the oil in them really deteriorate that fast?

 

[Buck Turgidson]

My 1970s 2QM15 service manual has 50hrs first change then every 300hrs thereafter. Got to be honest, I haven't changed the gearbox oil in 5 years and I guess that's getting close to 300 hrs

 

[Tranona]

The OPs gearbox will likely be a TMC40. Manual here betamarine.co.uk/resources/Gearboxes/TMC/TMC40P-OM/#page=4 first change after 30 hours then every 500 or annually. incidentally same for PRM, although the latter is much more robust and with 50% greater capacity.

 

[Koeketiene]

Yanmar 3YM30 - I was advised after 500 hrs or every other year (whichever comes first).

 

[vyv_cox]

When new gearboxes are first run they generate a lot of ferrous debris from teeth sliding across teeth. Machined surfaces inevitably include many minor imperfections, known as asperities, but these soon go. It is very common for the first oil change to be required in 50 hours or so to remove this debris and avoid circulating it.