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Old 02-22-2008
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Rebuild vs replace diesel engine

Latest copy of (Australian) Cruising Helmsmen has an article replacing or rebuilding a diesel engine ("Fix it or flick it"). Not a bad article, however one section I don't agree with is this statement.

The first question to ask is: how old is the old engine? If it's heading towards the 20 year mark then even talking about a rebuild is probably not a good idea.

The article gives a couple of other reasons for not rebuilding (ie damage to the crank shaft, pistons rings, etc) however the main issue stated is age with 20 years being the magic number. I would of thought a number of other issues would come into the decision including:
  • engine hours
  • how well the engine has been maintained
  • how easy it is to obtain spare parts
  • engine access, ie can the engine be lifted out easily or do you have to dismantle half the boat to get at the engine
  • etc, etc

The two most important ones would be engine hours and availability of spare parts.

For example, my boat has a 98HP six cylinder Nissan SD33 diesel engine installed in 1979 (29 years old). Engine is keel cooled (ie cooling water circulates though pipes mounted on the outside of the hull - no saltwater through the engine). Engine has around 2,700 hours, of which I have done about 150 hours over the last 2 years. When I brought it two years ago had it inspected by a diesel mechanic, who gave it a clean bill of health. Have had no problems with the engine during this time. Spare parts for this engine are readily available (it's the same engine that was in the Nissan Patrol from around 1981 to 1989).

Over the next 2-3 years one plan is to remove the engine as part of a major boat rebuild and have it either overhauled or replaced, depending on how the engine has gone, what the inspection shows, etc. However according to the article replacement would be the only option.

Any advice / opinions / comments?

Ian (ilenart)
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