Predicting the Future

When confronted by a complex system in an unknown state that you need to deal with into the future there is one thing you should do first: establish a baseline. It could be a used car, an existing server, a relationship with your favorite other human or a totally abstract situation: the first challenge is to establish a baseline. A baseline is just a bunch of key measurements chosen to provide a good indication of the state of the system and that you can repeat at intervals. Once you know the interval and the difference between the baseline and the current value, you also know the rate of change and with the rate of change you can start to make predictions about the future.

The system I need to deal with now is the engine. This is a Volvo Penta MD22l, made by Perkins in the UK. The basic engine was used in vans and small trucks and even the famous London Taxis. It is a conservatively designed overhead cam, mechanically injected, normally aspirated diesel. I now know what all those terms mean too. Basically, it should be cheap to run and last 'forever'. But nothing lasts forever, especially when it has not been maintained and lives in an environment of fire and seawater. 

Having very little experience of diesels I needed help. I spoke with several marine mechanics, all of whom took one look at it and said 'aw, should be ok' and left. Not exactly confidence-inspiring. Looking back, I think they took one look at the tiny engine compartment and the way the engine was hemmed in on all sides by other equipment, like the refrigeration compressors, and ran a nautical mile. I very nearly didn't buy the boat because of the way the engine compartment restricts access to the engine. But I also saw that by removing the old refrigeration gear the access could be improved.

Fast forward a few weeks and the refrigeration system has been upgraded to 12V DC. The only remaining items of the old refrigeration system are the engine-driven compressor and a heat exchanger, both redundant. Access to the engine is now much better.

Royce, the shipwright, suggested I call his mate David Short. When David looked at the engine, in his quiet way, he set out a plan of attack "Pull off the exhaust elbow and check for corrosion. Remove the raw water pump and service it. Remove the redundant refrigeration compressor pump and rebuild the power takeoff mounting. Remove the redundant heat exchanger. Replace the timing belt. Change the oil. Fix these three diesel leaks.

"Work from the back of the engine to the front" he said "Finish one job before you start the next."

My heart sank. I was kinda hoping he would wave his magic wand and say "Everything is perfect, wow you got a good buy here, nothing to do, you don't even need to change the oil for another million hours". 

Fast forward several more weeks. It is done. David Short is a mechanic with many years experience and a great deal of understanding of the ways of marine diesels. He must have x-ray vision too, because he somehow knew the weak-points of the engine. The raw water pump and the exhaust elbow were dangerously corroded and needed total replacement. The old power takeoff was only held on on one side, the bolts on the other side having fallen off. Andrew, the excellent local boilermaker, rebuilt it completely out of stainless steel. And there were many poorly fastened items I found along the way. I shudder to think what would have happened on a future trip if I had not followed David's advice. 

And the bonus is that I now I have some familiarity with the mechanical monster in the bilges. I am not a mechanic, so doing this work myself was slow, difficult and put a strain on my aging arms and shoulders. I hope I never need to repair an engine at sea, like Gerry Clarke had to do again and again in Totorore. In fact, if the engine broke down at sea I would be unlikely to even try. Instead, I would try to sail to the nearest port. But I have established something of a baseline. I know the basic engine systems are in good repair and I know the service intervals required to keep them good. So I hope I can make one prediction about the future: the engine is less likely to break down.


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    Even my engineering skills are quite inadequate to follow the difficulty you faced, I must admit I admire your persistence in attacking all the jobs put in front of you. I like the word "Baseline" something we all should establish whatever our direction in life.

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    Dave, writing about ones woes is always a wonderfully cathartic experience, and along with your new found baseline, will I'm sure hold you and the engine together into the distant future. Oh and well done.

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