Been patiently waiting for someone to take the bait on this one. Since no one has, I’ll step up and put the target on my back. My experience with diesel engines goes back to age 6; my marine diesel experience is considerably shorter. Either way, I will not attempt to answer your questions with specificity because, in my opinion, they are unanswerable. Others may disagree.
First, there is ample information on the topic posted in many, many threads over a long period of time about DD longevity; the opinions run from soup to nuts and are all probably somewhat right and wrong. Second, how you treat your motors largely determines how long they last. The second part is the easiest. Stay ahead of maintenance; give your motors clean air, oil, coolant, fuel and don’t forget sampling. Stay at or under 80% of loaded WOT for continuous duty; run your engines regularly and bring them up to operating temps when you do so. Don’t load them cold, and don’t shut them down hot.
The third part deals with definitions, and it’s the trickiest. What is a major overhaul anyway? Was it a top end, short block, bottom end, in-frame or …? One yacht broker claimed a major was 12 new injectors and 2 new turbos on a 1271! Did the head(s) get sent out to be checked? Valves? Water jackets? Did they check the head for true? Did the crank get pulled and mic’d and checked for balance or did they just roll in new mains? What about the cooling system, the air charging system? It goes on an on. How about the gears? So what constitutes a major overhaul on a marine diesel? I’ll be damned if I can tell you. Same thing on heavy equipment and farm machinery—it’s just easier to get to everything and record keeping seems to be a lot more important.
When I hear 50 hours SMOH, I think of my recent post on a boat I looked at:
"In 2013 an '80's model 55C came on the market in Charleston for $199K-'both engines recently majored by knowledgeable mechanic.' I estimated it was worth maybe $130K and was laughed at--I was lucky. I forgot about the boat for 2 years, then I saw it at a dock. New listing was $50K OBO. I found out both 1271's had cracked rings SMOH. $30K could have probably bought the boat. Another $75K for complete major and then who knows what else. Caveat emptor bigly."
Well, the boat was owned by the owners of a tugboat company with their own in-house mechanic. The motors had almost no hours SMOH when multiple rings cracked. Likely the mechanic used the wrong tool and stretched or flexed the rings on installing. So unless the “major” was done by a dealer with complete records and maybe a warranty, I’m not too impressed with low hours until the motors have some quality time underway.
So what is a major overhaul?
Then when you’ve figured that out, tell me when a major overhaul is due? How many hours is that? Maybe it’s due when the motors are laying down a smoke screen or maybe just don’t instantly start on a cool morning. Maybe a block heater would help. Would $100 versus tens of thousands influence the number of hours? Maybe your starter is just worn down and won’t give a tired or even a good motor quite enough turns to get going? We are talking about recreational boats after all.
I realize I may come across as talking down to you. I apologize if so. There are just so many ways this could go. How about this? I buy good shoes—Allen Edmonds. I haven’t bought a new pair since the early 1990’s. I keep them shined and put new bottoms on when they’re needed. I’m looking at wearing the same dress shoes for thirty years. Some people can wear a pair of shoes for thirty years and some can wear the same shoes out in no time at all. So how long does a pair of shoes last?
About as specific on a Series 71 as I can get is this: If one motor needed majoring after 1100 hours, something is seriously wrong somewhere.
Batter up.
