We are in the throes of re-powering Morgan’s Cloud, and as far as we are concerned, this unpleasant and expensive task has come about 4000 engine hours too early.
A couple of years ago we started to notice that we were getting much more soot on the transom from the exhaust than we liked. Then last year we started to see un-burned fuel on the water aft of the boat and coating the dinghy. Clearly all was not well even though the engine continued to start easily and run reliably, as it always had.
We pulled the injectors and had them rebuilt. We pulled the injection pump and had it calibrated and rebuilt. Still the problem got worse. Then we started to lose top-end RPM, a sure symptom of loss of power.
Finally we did a blow-by test in which we measured the amount of gas pressure in the crank case. Oh-oh, off the scale. Either the valves were not seating properly or exhaust gas was blowing by the rings. As the head came off, we hoped for the former—a comparatively easy fix with a valve job.
But it was not to be. David, ace machinist at Billings Diesel and Marine, checked the cylinders for wear with a bore gauge and discovered that they were out of round. And that’s when it got weird: The cross hatch pattern that was etched onto the cylinder walls during manufacturing was still in almost perfect condition, indicating that there had been no appreciable wear. Further, we had never overheated the engine and the oil samples that we had analysed at every oil change had never shown excessive fragments.
A vague bell went off in my memory: When the engine was new we had a problem with fumes in the engine room. I measured blow-by at that time and had even written the result in an old log, which, miracle of miracles, we were able to find. The reading: 8 inches of water. At the time, I had called Cummins North East (CNE), the dealer that sold me the engine, to ask about this reading and was told that it was not a problem and that the maximum for a new engine was 12 inches. But the Cummins document we found last year seems to indicate (it is not as clear as one would like) that 3 inches is the maximum for this engine!
By the way, CNE then sold me a crank case re-breather system to solve the problem of exhaust in the engine room, which never did work well until heavily modified by Billings.
All of the above leads to one inescapable, at least to us, conclusion: The engine was bored out of round when new—a lemon, pure and simple. Even if that was not the case, this kind of problem at 6000 hours on a diesel engine that has always been meticulously maintained is just not good enough.
This comes on top of another manufacturing mistake by Cummins (stripped bolts on the oil pan) that we experienced with the same engine.
As we always do with this kind of post, we offered Cummins and CNE the opportunity to comment. They wrote us a brush off email.
Comments are closed on this article.
My neighbor once brought home a brand new Alfa Romeo two seater that was full of engine problems from day one…after numerous inconvenient returns to the dealer for adjustments and so forth, the regional service honcho was called in only to discover the engine was improperly aligned with the drive shaft at the factory…they honored the warranty and refunded the purchase price of the car, but my neighbor laughed at the idea of replacing the car with another Alfa after contending with such a basic and catastrophic assembly error…moral of this story and yours: never accept even the slightest anomaly or doubts with anything new especially if it is mechanical…I know you are more than upset with this development especially after showering this engine with such constant tlc expecting only the best in return…now I have a better understanding of the wisdom in Lin and Larry Pardey’s long-standing decision to go engineless with its inherent drawbacks such as the urgent need to fend off from a lee shoreline or on a close collision course with another vessel, which, for them, is more likely to be much bigger and harder…on the other hand, Larry is the least likely person I can think of who would ever wind up in such situations…hang in there as I know you will…Richard in Tampa Bay (Cavu’s master and commander…26′ Bayliner pocket cruiser i/o)
Hi Richard,
Good point on not accepting any anomaly on a new piece of gear. Problem was that Cummins specifically told me that the blow by I was seeing was within spec.
This is a sad tale, and one that every marine engine manufacturer needs to read. The problem is that barring few exceptions engines for boats are simply commercial engines fitted with unique cooling arrangements (Marinized). If the engine were in a static application (say a genset) there would be no reason to re-furb/replace. Being in a boat the fumes issue was always going to be a problem, and reliability is paramount. These low hours does suggest an early failure. I am certain that you have the fullest service records, and since the ‘hatching’ still shows on the bores I would address this problem with the US Cummins concession. Cummins have a vested interest in their reputation and should at least investigate this early failure.
Nevertheless I would still opt for a rebuild. This engine is a ‘baby’ and has many hours running available. A rebore to the next size piston is a certain cure, but if there is ovaling the bore dimensions will have to be checked once enlarged. Replace the bearing shells whilst you are at it and undertake a ‘top end’ rebuild. Will Cummins pay for this, or at least part of the job?
I guess there will be more yet to this story.
Hi David,
All very good points, thanks. Clearly you are knowledgeable about engines and you are with the majority of experts that we consulted on the rebuild. Next post we will look at the whole rebuild or replace decision.
Hi John
Sorry to hear about your boat motor. I have a fleet of pickup trucks with Cummins motors and find them to be very good but, and that’s a big but, the last 2 that I have had are an ’06 and an ’08 and have had trouble with both of them. I don’t think I would buy another one. Love reading your blog; very informative. Newfy in Tucson
I had a Cummins 6BT5.9 in a previous boat. Suggest you contact Tony Athens who runs the Cummins Forum on “boatdiesel.com”. I found him to be the best source for tech support on these engines and an unbiased, straight shooter on problems. Good Luck.
I would be very happy with the rebuild route proposed. Bigger/oversize pistons/new x hatch/new big and small ends, grind valves, pump and injectors. But then we rebuild these engines beside the road in East Africa and get 250,000 kms plus from a makeshift repair. Cummins is a good block with what should be many hours of life. I wonder if this is an “Indian Cummins” as we had Ingersoll-Rand deliver compressors from India with a Cummins motor that died rather early….. As a boat rebuilder it is easier to remount the same engine on the engine bed after a rebuild and this would be a factor in my decision.