Bukh gearbox BW6 oil level indication

[April's keeper]

Oil capacity 0.5l, as stamped on id plate. I have filled the box with 0.5l of engine oil and get the correct reading on the dipstick, however when the output shaft has turned and I read the dipstick it shows massively overfilled. It is only when BOTH dipstick and filler plug are undone does the oil level go back to the correct indication. This is fine as the gearbox is on the bench. It is not fine when the gearbox is back in the boat. The pressure relief valve on the rear of the box is not blocked but the spring is holding the rubber pad against the vent nipple. Does anyone know what is going on?

 

[neil_s]

I can't give you an explanation, but if it's any help, my BW6 is the same.

 

[April's keeper]

I can't give you an explanation, but if it's any help, my BW6 is the same.

Thanks for your reply, at least I know I am not alone. I guess I will not be checking the gearbox oil level so often, at least it is quite visible and I can see if it is leaking.