Yanmar SD40 Saildrive Seals Replacement

[Leo Morrison]

I would like to know when it's time to replace the Saildrive seals of a Yanmar SD40 (by seal I mean the diaphragms A and B in the Yanmar service manual). In the same manual it is recommend to inspect every two year and change if hair cracks are present, while Volvo recommends replacement of saildrive seals at 7 year intervals. Does anybody have experience how complex /costly is such maintenance and if there is a period after which is highly recommended to replace the seals.