twin 16v92 ddec rebuild costs and time?

I am buying a yacht with twin 16v92's. Non turbo I believe. I am getting from a bank after a default so I have not actually even started up the engines. I talked to some people at the dock who are familiar with the yacht as well as the boat broker, both say they were running fine last time they were started but... 4,000 hours on them both.

I intend to do a survey after purchase, but I can not before.

So is 4000 hours a lot?

I am guessing it is... would they most likely both need a rebuild?

And how much does that cost?

After a rebuild, are they like new or what should I expect?


What other items would need to be rebuilt at same time, transmissions of whatever the marine version of one is? What else and what costs?

Yes, I am new at yachts so please forgive my ignorance... I am getting what I think is a very good deal, just want some info on what to expect with 4,000 hours on engines, what most likely is worn out or will wear out soon... and the costs to repair.

Any help is appreciated, and thank you.

I don't know that engine very well, but the main question is likely to be what HP rating they are at. I have a 12V71 that did 30,000 commercial hours before needing a rebuild, but it is a non-turbo 14l engine that makes just over 300hp. Keep it cool, change the oil and you may never wear it out. Take the same engine with turbo and aftercooler to get 875hp and it might be done in less than 4000hrs. If the transmissions have been sized properly to the HP they should be good for a while yet (assuming proper maintenance).

I assume that the boat isn't very new given the engine style so don't forget that there is a lot more to a boat than it's engines.

92s don't go as long as 71 series, but if it's a natural (no turbo) and you spare the horses it could easily go 10,000 hours. Maybe more with clean oil. If it's turbo, worse yet dual turbo, 3-4,000 is probably past the rebuild time. A few years ago I rebuilt 2 IL671 naturals for under $10 grand. Heads and injectors were done by professional rebuilders. I did everything else, engine kit, other bearings, seals, blower, pumps, and assembly. Engines had somewhere above 20,000 hours. I ran a number of Detroit 71 turbo engines commercially. With clean oil and keeping the engines below 80% of hp, I doubled engine life over what other operators were getting. I have done my own engine work since about 1969.
Excessive heat in the cylinders and passing over the valves is what limits engine life. Naturals, even at full rated hp don't get that hot, but turbo engines do. My current naturals were commonly run at 300 rpm over the maximum rating by previous owners w/o problems.
An engine kit for a 16v92 from when I buy some parts is about $4500. From Detroit probably double. Having a mechanic rebuild one of those engine is probably $20 grand. More like $30 grand if a Detroit mechanic does it. If you can find a mechanic in a fishing port that knows Detroits, you'll get a good rebuild, maybe for less. I believe that engine is 2 - 8v92s bolted together with common crank and cams. It has 4 - 8v heads, same pistons, sleeves, injectors, so common parts.
Turbo 71s go about 3000 hours with hard use. I usually got 7,000 hours and one made 10,000, but again, I run clean oil and baby my engines. Going out fishing in a sport fisher at 25 knots instead of 30 knots will just about double engine life.
I don't have much experience with 92s but basically a larger version of the 71s. Nice design, very reliable for the ocean. All mechanical, no injector pump, no electronics, etc.

You'd buy a yacht in this class without a survey???

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