I replaced the prop shaft on my Santana last year and found it was blessed with a stuffing box that was completely stuffed so I invested in a dripless seal supplied by a South Australian company. It works brilliantly and I am very pleased with it, however, I've heard that when these things fail they fail 'catastrophically' so I need to know what to look for as an indicator that trouble is imminent. If you are on board when it happens there is a 'failsafe' device you can operate to stop the ingress of water, but if you're not, well........So what do I look for and how long are they supposed to last for?. I thought engine heat may be a problem but the seal is filled with water so it should stay cool. Anybody with experience with these devices?.