2 cycle vs. 4 cycle Detroits

It depends on who marinized them. J+T 12v92's lasted the least longest. IMO, they go about 1000 hrs and it's rebuild time. Sometimes less, some people have gotten good hours out of them, but it seems to be the exception. A lighter boat that cruises fast, they seem to last longer. I managed a 63 ocean where they lasted just under 3,000 hrs. The other problem are the reliabilt parts are not that good anymore......injectors, cylinder heads, etc.........I worked on a 58' Striker SF with 12v92 JT's (johnson and towers) and it had 8 sets of majors from 1991-2004.

SAY WHAAAAAAAT?

I can't speak for the credibility with the part manager i spoke to a few days ago but he was saying that the whole issue with parts for these 2 cycle engines became a problem once MTU bought out detroit because they pretty much told everyone that they weren't really planning to support the engine and that they would manufacture their own parts for this engine. Apperantly there was a big fight about this and the government pretty much stepped in and forced MTU to mass produce parts for these engines. (Government has MANY of these engines in their fleet and need parts for obvious reasons) Now he was saying things are slowly getting better but MTU put a lot of old detroit supplier and part manufactures out of business with their stunt so now that things changed there are few people left to meet the demand. So long and short things are slowly getting better but it will take some time.

I have a 52 hatters with 92 series engines. parts are still available, it just sometimes requires special order. This whole thing is simple supply and demand. These 2 cycle engines are EVERYWHERE. Look at any hatteras, viking and bertram boat in the 80s and early 90s and over 50% of them are 2 cycle detroit. There is simply too much demand and profit in this market to abandon the engines.

+1

No worries, cabobo09, you're new here; you'll get used to the misinformation over time.

Used to be, Detroit Diesels were marinized on the distributor level by J&T, S&S, FDDA, et al. In 1988, when Rodger Penske took over, he had the marinizations done at the factory, because some of the distributors did dumb stuff causing warrantee headaches...like the infamous aluminum exhaust manifolds offered by one NJ outfit, ahem.

The Series 60 was a big hit for their four-stroke line albeit primarliy for the on-road applications where cranes are more accessible: the single head weighs a ton and does not make for an easy top-end overhaul compared to ANY of the two-stroke engines.

There are parts suppliers for DD parts here in the USA. Be careful, though--buying cylinder kits off fleabay might be trouble as cheapie Chinese knock-offs do suffer premature failure. I have personal experience here. Perhaps the odd 63 Ocean as well.

Everybody and their pet duck knows how to work on the old 2-stroke motors, especially the pre-DDEC models, handy when stuck far from your local DDC-MTU shop.

Yes, that is correct. The boat travelled and fished A LOT. It was a VERY heavy 58' Striker SF (22' beam) built by the Burger yard in Lantana, with Johnson and Towers 12v92 TA's, J+T was known for well making more HP then the other marinizers of DD's, by adding larger turbo's, bigger injectors, etc. then say Covington, S+S, etc etc. It had 8 sets of majors between 1991 and 2004. The name of the boat was Sweet Revenge, then became Mary Ann, and now I don't know. I was involved with the boat from 2005-2007, however I knew the first owner who had it built and owned it until 2004.

I also ran a 1997 54' Hatteras named Tebo down from Stuart a few years ago. It had 12v92 DDECs, which were majored by the DD dealer up there at 980 hours. I ran it to Fort Lauderdale and it had blown the port engine at 1932 hours on the survey and seatrial with the buyer, who adjusted price and took delivery of it. So it was ready for it's second set of majors at exactly the same time frame, another 980hrs.

On the other hand, I managed a 1987 63' ocean, that one and the owner's brothers 63' ocean both went 3,000 hours before majors on their 12v92's. BUT we're talking about a boat that cruised at close to 30 knots.

As for the DD reliabilt parts. One engine 12v71 TI was majored by a well respected DD dealer in South Florida in 2007. At 100hrs we started getting a little black smoke on that engine at cruise. Dealer came out checked everything said it was normal. Ok, well I'm taking the boat to Chicago, engine now has 150hrs on it in 2008, we get just south of Coinjock, NC and the smoke trail goes from a #3 (out of 10) to a #9 out of 10, I limp into coinjock, call the dealer in VA. Western branch, limp up to VA. Split tip on the injector on #4, no compression in #4. The dissassemble the engine, 4 of the sleeves have bad were on one side about an inch wide all of the way up and down the sleeve, 5 out of 12 injectors are bad, and 1 reliabilt head has a few broken valve seats. They did both fuel and oil samples and said those were fine. Needless to say they rebuilt it again with DD parts and the motor is fine and has 800hrs on it. I've heard of bad batches of reliabilt injectors and such...........during a certain time period.........

The first 150 sets of 16v2000s had many come apart due to defective rings from the factory and came apart within 250hrs, the latter ones have all been pretty good. I had a 2006 set of series 60's that were less than 2yrs old and under 300hrs, have both aftercoolers leak, both intake manifolds leak......they were fixed under warranty and ok afterwards.......

Generally speaking the older 2-stroke DD's are very reliable and have good longevity. But, the more HP's squeezed out of them, the shorter the life. A 6V92 Ta at 475 H.P. will go 3000 hrs easily. The same engine producing 550 H.P. will die around 1000 hrs. Obviously good maintenance is key to longevity. They may not be as economical as new technology 4-strokes, but no computer needed to diagnose a problem!

Capt J was that a De Groot designed Striker? That beam 22' seems too wide for a 58'. Must have been incredibly stable on the troll. Any pictures out there of that boat?

To the OP the high output 2 cycles are not bad engines. At full rated power there is very little room for error in the cooling system. On top of that they were often undersized or overloaded for the application. In a setup where they can make rated RPM + 100 with the boat fully loaded they will last a long time if run no higher than 80% of rated RPM. If you find a boat that has needed majors in under 2000 hours then it probably needed more motor to begin with.

On the other hand there is probably no motor more likely to get you home no matter what happens to it than the non DDEC detroits.

Good luck

Yes, my theory is what really leads to an early death for the 92 series is a heavy yacht, that in a sea, see's a large change in load factor. For example that striker cruised at 20 knots at 1900rpms, BUT in 5' seas when it climbed the wave it slowed down to 17 knots, then sped back up to maybe 21 knots on the way down the wave.......

The boats I've seen them last a long time, at least the SF, are the ones that cruise at 25+ knots.......they see less load factor changes. Also in situations where they are slightly underpropped. This is solely my experience and opinion. They also last a long time in the non DDEC ones when cruised at 1900rpms or more even 2000, because the injectors are so big they don't meter fuel as effectively at say 1700 rpm cruise.......

I also saw a 58' searay with 8v92's DDECs that had a dead hole in one cylinder in each engine at 800hrs.......

I was told (by a very reputable 30yr DD employee of a dealer) that the 550hp 6v92's only go 250hrs, then they need a rebuild......he says they may go to 1000 rpms, but they start to lose...... 20% HP through the rings and stuff at 250hrs.......

I really like the 71 series, but am not a big fan of the 92 series. But then again, I have also seen lots of 92's running around with lots of hours on them as well.......

I think my S&S 16-92's are great in the 65 Donzi. I could have a higher cruise speed with 3 inch shafts instead of the 4 inch, but so what. Non DDEC is great.

Not as easy to get the power as one might think. Yes changing a cylinder kit or replacing a head is just matter of bolts. But replace a blower or governor and it's a different story. I personally have seen many old time detroit mechanics missing fingers from improperly tuning engines that have run away upon start up.
As to how long they live, the more power you want the shorter the life.

On the other hand the DDEC-60 is probably the most proven longest lasting engine on the market.

Non-DDEC 16-92s? I thought all 16-92 and 24-71 engines were DDEC.

Nope. I've seen non DDEC 24v92's as well as non DDEC 16v92's.

I think it was about 89 or '90 when DDEC came out. My 1987/8 Donzi with S&S 16-92's are non DDEC, and I would much rather have them than the DDEC versions.