Diesel Engine Longevity

14 Aug

The meter on my Perkins 4-236 diesel engine just turned over 12,000 hours, and I’m only responsible for about 4000 of this. Over the course of forty-five years and a circumnavigation, Charlene (I don’t know why my diesel engine is named this) has had routine maintenance, and lots of components replaced, but she’s never been rebuilt.

In the fifteen years I’ve owned the boat, the engine has only failed to start with a touch of the key twice: once because it was too cold in New Zealand, the other a few weeks ago when the starting battery was shot. That’s what I call a reliable piece of equipment.

Diesel engines are truly remarkable in their simplicity and reliability. They say that with a snorkel air intake, a diesel can run underwater. Diesels make their wasteful gasoline burning cousins, with their complicated electrical systems and wimpy compression ratios, look like Rube Goldberg contraptions.

Ten to fifteen thousand hours seems to be the zone for rebuilds on diesels in the boating world. This is a lot of hours! My four thousand hours over fifteen years and a circumnavigation equates to roughly 25,000 miles of motoring, and this only represents a third of my engine’s life.

As long as we obey the Holy Quad—clean oil, clean air, clean fuel, clean engine—as expressed by routine maintenance, we can all expect long, happy lives from our diesels before they need to be rebuilt.

And rebuilding isn’t the end of the world. A complete rebuild kit for my Perkins 4-236 costs less than $1000. The problem is getting the engine out of the boat (not entirely necessary, but probably recommended) and all the labor. If you’ve got the space (t’would be nice to have some dedicated shop space), and the time, anyone can rebuild their own engine with just a few key jobs sent out to a machine shop.

Herr Doktor Diesel, the inventor:

But I’ve had another test case throughout my life, our family business, the Balboa Island Ferry. We recently had to replace all the engines with California emissions-compliant John Deere diesels, but for the sixty years before that we ran six cylinder Fords.

There are three ferries, and we keep two spare engines in the shop. One of the spares is completely ready to go—plug and play—the other is a rebuilt block, which would need a cooling system, starter, pumps, et al before it could be put into service. We can drive a pickup truck with a hoist onto the ferry to swap engines. The record for this operation is three hours, on a 4th of July, when we had cars stacked around the block and down Park Avenue.

Given this quick turnaround for engine swaps, we run our engines into the ground, and I can’t recommend this practice for a cruising sailboat in the hinterlands. And our engines represent a very different usage pattern than a recreational boat: these engines are run 24/7 sometimes, and could run though a whole life cycle in just a few years (there are 8765 hours in a year).

The average number of hours before a rebuild, over the course of sixty years was about 20,000 hours. Often engines would go to 23,000. The record was 26,000 hours. 26,000 hours! That’s three entire years running 24/7, and just before a rebuild: the same engine block and major components ran for all sixty years.

That’s what I call a reliable piece of equipment.


  1. Paul H Merry

    When you think, many small communities generate their own electricity, and often the generators are powered by diesel engines These engines are in the most stable environment imaginable,and are usually very well maintained, but they run year round twenty four hours a day. What I have heard is that they can go for many years without major service; though I don’t have any hard data on that. But this could be a benchmark.

  2. Clark

    Hi Ronald, That’s interesting that a newer (newer than mine) Perkins advises every 400 hours. Older ones advised every 150. I assume this is because oil has got a lot better over the last 50 years, and holds up better. There have been some new studies that show that the majority of engine wear happens right after you change the oil! And that oil filters work way better after they’ve been in use for 20 or 30 hours, and had a chance to clog up a little. Makes sense intuitively, but I don’t want to believe it. We want to think that spending money and taking action extends engine life. Sounds like your Perkins has a lot of life left in it, and then, I’m told in many cases you can then get a whole second life by just doing a top end rebuild, which can be done in place. IE just re-building head, valves, valve seats, maybe piston rings? But piston rings would mean detaching the rods to get pistons out, or at least high enough to replace the rings. Anyway, a Perkins mechanic of 30 years I know says that the crank shaft bearings and all that lower stuff stays bathed in oil, and often doesn’t really need replacement in a full rebuild.

  3. Ronald Merritt

    I have a Perkins M135 that has 18000 hours on it. I am a troller so most of the hours are at trolling rpm’s which average about 1000 rpm’s. Running hours are at 1700 rpm”s. The book says to change the oil every 400 hours, but I change the oil every 200 and change the filters and oil at 400 hours. The engine still runs great and very economically. At any rpm exhaust smoke is hard to see.

  4. Clark

    Hi Daniel, I change the oil and filter about every hundred hours, but let it go to 120 or so if it leads to a more convenient time and place…but that was when I was cruising. Now I do it every two years or thereabouts, because I don’t put that many hours on her anymore. I think the manual says every 150, and to change the filter every 300. A Perkins pooh-bah told me there has been recent research that proves that some large portion of engine wear, like 20%, all happens within the first few hours after an oil and filter change! Part of that thinking is that a clogged oil filter works better than a fresh one…to a point. In short, do exactly what the manual says and don’t try to outsmart the manufacturer, as we can assume they tested the engine for thousands of hours and many start/stop cycles and arrived at some conclusive data for longevity. On the Fords the schedule was about the same, but they’d be run 24 hours at a time sometimes, so the the schedules weren’t exact either. The only point that everyone seems to agree on, and all the data backs up, is that diesels like to be run often, hot, and hard. Cheers, Clark

  5. Daniel Sampiero

    what kind of maintenance schedule are you using for the 4-236 to get such longevity? (I’ve heard 50 hour oil changes from some, and 100 hour from others, I try to run on the owner’s manual specs when available) Also, What was the schedule run on the fords? I’m always surprised by people who repower or rebuild with only 3k-4k hours, seems like they’re not keeping on top of regular easy to do work.

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