I would tend to avoid a boat with 92 series engines also. My understanding is that a lot of the problems with 92 series engines had to do with their wet sleeves and sealing rings; is that in fact the case? I think 71 series engines are more reliable, although they are heavy and don't make much power for their weight. But they make the power they make for a long time, if taken care of.
(We had a thread a while back here having to do with 92-series Detroits. I think the dividing line on power was 485 or 490 out of the V6 ones and about 650 out of the V8 ones- beyond that and you had your choice of which would blow up first, port or starboard. Mind you, 71 series with the wick turned way up weren't noted for their longevity either, but most of those didn't come from DD- they came from hot-rod marinizers like Stewart/Stevenson, J&T, and Covington.
When I first got interested in boating, which was in the early to mid 80s, DD had the lion's share of the market. Some boats had Caterpillars- the only engine they built was the 3160/3208, which they kept increasing the HP rating of- and Cummins, which made 555s, 370s, and 903s in various forms. Most 903s went into Coast Guard boats, which says something about their reliability. But I'll guess that 7 out of 10 domestically built boats with diesels had Detroits.
In the higher horsepower end of the market, there wasn't anything else. If you wanted a big boat, you got big Detroits. (there were a few boats built with big Caterpillar sixes, which were excellent engines, but very few were installed) At one point there were 12 cylinder and 16 cylinder versions of the 71 and 92 series engines, all very heavy and fantastically complex with superchargers, turbochargers (two to four of them) aftercoolers, intercoolers, oil coolers, oil-to-water coolers, and if you paid extra, a water cooler for your mechanics to stand around. Because with those engines HP ratings and the inevitable short lives of essential pieces, you had mechanics around a lot. This was before the modern era of lightweight reliable four-stroke diesels. The engine designers could squeeze a lot of power out of the vintage Detroit design using forced induction and big injectors but the reliability suffered greatly.
The basic design of the two-cycle diesel dates back, I think, to Winton, who pioneered the concept in the thirties or forties. If you visit the Baltimore Railroad Museum, you can see vintage two-cycle diesels there which are retired locomotive engines. They look exactly like old Detroits. They are, in operation and nomenclature, exactly like old Detroits. You wouldn't want to be the guy who had to pick up and move one.)
I took Caterpillars out, while they had few enough hours to sell them, and put in Cummins diesels. No engine is perfect, but I think Cummins has their act together a lot better than Cat does. A 53 convertible with M11s sounds great. A Series 2 45C with M11s sounds even better- faster, a little bit more nimble, and better bridge setup. Either one would be a nice boat.
