The Offshore Voyaging Reference Site

Cummins Engine—Rebuild Or Replace?

Initially we were firmly in the rebuild camp, as were most of the experts we consulted. After all, at 6000 hours our engine is, in the words of David in his comment, “[a] baby and has many hours running [still] available”. Rebuilding would also save all the expense and aggravation of changing all kinds of things on the boat to make a  new engine fit. Not trivial in that the expense of such changes can run to half, or even match, the cost of a new engine.

As long as the repair looked like a valve job and maybe new piston rings, the price, while not trivial, was palatable at about $7000. An estimate based on doing it in Morgan’s Cloud’s spacious engine room without the expense of removal and reinstallation. Better still the boat was stored at Billings Diesel and Marine, one of the best in the business of engine rebuilds.

Bad News

But then we found that the cylinders were out of round and would require re-boring, necessitating removing the engine from the boat, complete disassembly, oversized pistons, and on it went. The price jumped to $11,000 and maybe as much as $13,000 if things did not go well.


In the end we decided to go with a new engine for the following reasons:

  1. The new engine at $14,500 was only going to be a little more expensive than rebuilding the old one.
  2. The new engine comes with a two year full warranty. While I’m sure Billings would stand behind their re-build, if anything new went wrong with the engine we could be out the re-build and still have to buy a new engine. A particularly worrying thought when dealing with an engine that has, in our opinion, had not one, but two manufacturing defects. (When the engine was brand new we found several oil pan bolts stripped. Cummins fixed this on warranty.)
  3. While trying to fix this engine, 3 out of 6 new or remanufactured injectors that we bought from Cummins  had to be rebuilt by a local fuel injection shop before they functioned. Therefore we were concerned that the parts we would need to use in a rebuild might be defective too.
  4. Cummins no longer makes this model of engine and parts are already becoming more difficult to get on a timely basis.
  5. We think we can improve our fuel economy with the new engine. (More on that in a future post.)

Do you think we made the right or wrong call? Leave a comment.

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It’s a shame you couldn’t have the rebuild done in another country at their labor rates. Ran 2 dive shops in the Philippines and used the 4 cyl 80 HP Fuso diesel bought surplus in Manila after life in a Japanese truck. Less than $1,000 US for engine and trans (4 sp manual) and less than $1,000 for new pistons, liners, rings, valves, bearings and labor. Rebuild 4 injectors for $40 US. Good quality work. About 3 years per rebuild with salt water cooling and basically trouble free with a stainless pipe heat exchanger. What about Mexico?



David Nutt

When we refit Danza, a 60 steel ketch, prior to our 6 year circumnavigation, we replaced rather than rebuilt the engine, generator, water maker, refrigeration systems, 100% of the wiring and plumbing and most of the electronics. That was just for starters. Danza performed in an outstanding manner all the way around. We spent our time cruising and exploring and raising our 4 kids as opposed to refitting in New Zealand, Australia, and Thailand. I am convinced you are making the right decisions. You already did the math.


Two years ago I made the same decision: i.e., to invest in a new engine. So far, my 3.5 hp Tohatsu outboard is working perfectly. Morgan’s Cloud may have picked up an engine destroying virus when she tied up at our guest slip in the fall of ’08. As a write this, Moonshadow, which ties up in that same slip twice yearly on her way up or down the U.S. East Coast, also is replacing her failed engine with a new Kubota. Cindy and I still welcome any cruiser willing to chance this possible infection to tie up at our guest slip just outside Annapolis, Maryland.

Doug (& Dale) Bruce

A no brainer .. but then some people have accused me of being one. Seems you’d also have a “brand new engine” if you ever decide to sell MC. And you’ll probably benefit from some technological improvements with a new engine, including better fuel economy that may help justify the price .. at least in theory.

Peter Bateman

In truck terminology, we spend 50% of the replacement cost of a truck on the rebuild of a new truck and this gives us 80% of the life again of a new truck before the maintenance reliability issues start to take a toll and we would sell. Your US labor rates tend to confirm that the US is a component change society, rather than repair and fix components. In your case, where you are and with the resale value, you have made the right decision I think. Ouch!


Agree with your decision to replace…hopefully you spurned Cummins though? R in Tampa Bay

don lake

John, just make sure it’s not a Cummins. Since I last logged in and left a note, I have had to put my 2008 back in the shop. Somehow the emission control stuff seems to clog the exhaust and it has to be replaced with a new exhaust again. They are not being very nice about it either wanting oil change and fuel receipts. I have a Perkins in my Jeanneau—it has been great. Good luck.

Victor Raymond

Oh yes, I totally agree with Doug and Dale and all the other responses. My only hope is that I would have done the same with the facts as they are, i.e. learn something from your experience.


You Guys made the right decision…stay away from Cummins. I have heard more positive vibrations from sailors with Japanese engines like Mitsubishi, Yanmar, etc. If not, a Swedish made “Volvo Penta” is in the picture! Good luck with your new power.

vince bossley

In my experience very few folks outside of the US would even consider a Cummins. Yanmar (very quiet) and Volvo Penta (including Perkins) are the superior marine motors for performance, reliability and longevity. I trust this is the direction you are moving now.
p.s. Check out the Volvo IPS (expensive) system.


Hello John ,
Hope you will make the replacement a John Deere. Some friends and Steve Dashew don’t have big problems.
Good luck, Bob

David H

Having made an early comment on this issue I have read again the later comments. What a sad tale and an appalling indictment of the Cummins brand. It brought to mind our recent engine experiences. After much consideration as to a replacement for our boat we bought a Saga (Saltram) 40. The boat had a recent replacement engine, a Beta 50. My initial reaction was that I would rather have a Yanmar. In time I have altered my position and now love the Kubota based red monster. It is far cheaper to run than the 56hp Yanmar, and substantially quieter. By no means in the ‘super league’ of marine engines, but is a definite consideration, and an economical choice. One major advantage is the engine’s simplicity and the ability to get service parts from any Kubota dealer worldwide.

Ed Seling

Don’t know if Beta is on your list of possibles but if it is beware of supply issues. I waited nearly 3 months for delivery of my new 50. (I did have them customize the mounts but this should not have taken much time as it was a simple task). I am not thrilled with the quality of the panel either and would consider rewiring with higher quality gauges if I had to do it again.


PS I think Westbrook’s dock, if it has some engine killing virus, has probably been disinfected thanks to our combined efforts!

Kit Laughlin


Not sure if you’ve written about this elsewhere, but what in your view caused the cylinders to be out of round? 6,000 hours is not a huge amount of work, in diesel-land.