When I removed the starter motor from my BMW D35 engine the first time and the auto-electrician found it to be badly corroded inside by salt water, I assumed it to be the result of old age. It had not been looked at during the seven years I have owned the boat and anyone’s guess as to how long before that. My Top Hat 31 sailing boat is now 22 years old. 
  It was painstakingly repaired, a replacement being unobtainable, reinstalled and duly fired the engine into life for a sail on Pittwater, but when we tried to restart the motor two hours later to find a mooring in Towlers Bay for lunch – once again it would not work. 
  Although it was New Year’s Eve, Michael Rich happened to be in residence at the Lovett Bay Boatshed and, with his usual kind generosity, he met us as we sailed into Lovett Bay and saw us safely moored there. A clean-up of the electrics could not get us going again. 
  The starter motor was later found to be wet inside once more. With the Christmas holiday rush and a long period of heavy rain, marine mechanics were fully booked – so Michael explored the possible causes. The bell housing, to which the starter motor is fixed to engage with the flywheel, was dry inside, perhaps the cooling water was somehow getting in due to corrosion or maybe a leaking welch plug? Another voice of doom proposed that perhaps it was time to consider a new engine anyway! 
  Seeing the possibility of big unaffordable repair bills looming, I asked Michael to put the boat back on its mooring in McCarr’s Creek and then started wondering how I might tackle the investigations myself. I first tinkered with car engines as a small boy with my father – but in the 1940s and ’50s they were far less sophisticated than now. 
  Fortunately I have a good friend who has a collection of classic cars, a comprehensive tool kit and a penchant for this sort of thing, and together, after much chinscratching, we devised a way to suspend the 260kg engine with blocks and tackle from the boom and in through the companionway. We propped the boom off the cabin coachhouse and managed to take the weight of the engine off the mountings. 
  Even though corroded, all the bolts finally moved after much dowsing with penetrating fluid and we were able to disconnect the prop-shaft and remove the bell housing and gearbox in one piece from the engine block. 
  Our task was made much easier by finding a spare parts manual with blow-up views of all the component parts of the engine on the internet, a free download what’s more. 
  We found no leakages in the system at all – through the engine or the gearbox – but the edge of the bell housing where it abutted the engine block was corroded, sufficiently to allow water to find its way from the block through leaky pipe joints, to get onto the flywheel and thence thrown up into the starter motor. It was made worse by the fact that the thin wall of the bell housing protruded above the top of the engine block, reducing the sealed interface area even more. 
  Everything is now reassembled with freshly painted parts and well-greased bolts. The bell housing is repaired with plenty of sealant onto the engine block. Needless to say all water pipe joints have been doubly checked for leaks. 
  We are looking forward to some winter sailing to make up for time lost during the summer, but perhaps with all that rain we did not miss that much!

Thanks for their invaluable help and advice to Michael Rich, Lovett Bay Boatshed; Frank Rubino, Pacific Auto Thornleigh; W.u.H Kuenzler GmbH – BMW marine sales and service (for their website) and Andrew Hyden (classic car enthusiast) of Turramurra.