Detroit 71 vs 92

I did an internet search and came up with the following attachment. It essentially is a rebuild kit for series 71 and 92 to make them compliant, but not certified, to EPA Tier 2 emission levels, only for commercial applications. You will notice that the power ratings are on the very low side, and these are engines that are not typically used in yachts, unless it would be a passagemaker/trawler type.

I have no idea as to how successfull the kits are as the company's website is not fully functional.

I think:

One major difference is that the 92 Series has a wet liner and the 71 has a dry liner.

That means that the 92 has coolant passages in the block that allows the coolant to directly contact the cylinder liner.

The 71 is dry fit into the block and no coolant comes in direct contact with liner.

The 71 is considered older and more reliable.

If I would consider either 71s or 92s if I were looking for a DD powered boat.

When I purchased my current boat, I looked at several boats w 6/92s and 671s.
I ended up buying the boat with the 671s.
The 71s worked better for me for a bunch or reasons, the significant factor being inline vs V6 reliability! Space, and number of parts.

Both are good engines. The largest factor in buying a boat with either of these engines is finding a qualified mechanic to work on them. Not a lot of us around anymore.

Speaking of "bulletproof".

Here is my 12V71TI cylinder head on its way to the shop for a failed "injector tube" ... yet another of the many ways these engines can fail.

Fortunately, it looks like the work will be limited to re-sealing/replacing the injector tube and reinstalling the cylinder head.

After the first two overhauls of this engine (in 200 hours) I learned how to quickly remove my salon couch, carpet and hatch cover for total access to the engines. Now it's been another 250 hours or so and the engine is coming apart again. Doesn't even phase me anymore. Just another day.

Bert, you are overdue for some good luck. better play power ball tonight.

I hope it's NOT the same shop doing the work. I would really question why are you having this problem if the motors were truly overhauled. Properly overhauled heads include new tubes that should last near forever.
I am sorry that your having extra problems in less than 250 hours. But this is a strange failure that should of not happened after a proper major.
Good luck, sleep well and dream of large women.

,Dread Pirate Ralph

Why did the injector tube start leaking? I find that to be strange if the motor was recently rebuilt. They should have been changed and usually they last near forever and you only have a problem once in a blue moon if you're removing injectors, they either get stuck in there or you have a problem when removing an injector.

The Injector Tube life should be at least equal or greater than the hours accumulated between complete overhauls. If the tube failed in combustion, they most likely were not reamed properly, if it is a coollant failure, they most likely were not installed properly or the heads have started to fail.

Has the condition of the head been checked/verified - any cracks that may lead to additional coolant type failures. Having rebuild issues at 200 hours (is tha right?) lead me to think that there are some outside circumstances going on - is your mechanic an independent or associated with a dealer/distributor? What is his track record / reputation?

As an aside note. DD did have some troubled blocks once in a long while. I've seen blocks from the factory where the bores were egg shaped and not perfectly round. I've heard of blocks with other machining issues. I've also seen these particular blocks get rebuilt a few times and having issues a few times, because nobody fixed the initial issue that was wrong with the block in the first place.

We'll see ... the engine was overhauled this last time by John Carey himself on the stand in his shop. New cylinder head castings were used. John checked all the tolerances and bored the cylinder bores. I'm confident that John will figure it out. At this point, it looks like there is no further damage to the engine.

I have certainly had my share of bad luck with this engine.

#1 .. $65,000 overhaul by Saunders Yachtworks of Orange Beach, AL ... Failed immediately. Saunders took no responsibility at all. They are the worst shop I have ever had the misfortune of patronizing. May bad karma forever haunt them.

#2 .. Larry Kress of Central Marine, Herrington Harbour, MD took $25,000 to remove the engine from the boat and leave it in pieces. Went out of business. (7 months of heartache)

#3 .. Complete overhaul on the stand by John Carey of Carey's Diesel, Leipsic, DE. $45,000. Took it from basket case to running in the boat in a month. Great guy ... nice business.

Now the cylinder head failed. Hard to believe and I'm sure they're not happy about it either. I called Carey's on Monday ... they had the cylinder head off Tuesday and back in their shop. I think she'll be good to go in another week. I am confident Carey's Diesel knows what to do.

Mike

What was the failure with the tube? Water leak? Blow-by? How was it detected? Who actually put that head together?
It's an Inquiring mind thing.
,rc

Carey's built the head up from a new casting. I detected the leak because the Walker Air-Sep Drain Tank filled with coolant and started making a mess. I also noticed coolant overflow from the coolant cap on that engine.

They have not yet determined what caused the failure of the injector tube. They may still determine something else is wrong ... cracked head etc. So far, though, it looks like leaking injector tube.

Western Branch Diesel (Portsmouth, VA) has majored both of my 16-92 mains and they were low overall cost, they stood behind their work, were on time and they operate as designed.
I give them and the non DDEC 92's a thumbs up.

I too had the pleasure of sitting at Western Branch's marina and having a rebuild done on a 12v71. I agree that they did very good work. Sitting at their marina sucked though. No ammenities and nothing nearby.....but nonetheless, the work was good and was done May 2008 and the engine is still doing well 1000 hrs later.... It took them about a month to do the work and there were zero issues with them keeping the yacht clean or anything else.

Thanks ... I almost moved the boat down to Portsmouth VA for the overhaul .. they were very uneasy about taking the basket case job (understandably) but were prepared to do so. I'm glad your engines are running well and the members of this board can all benefit from good references!

Here is an update on the engine.

It seems that the cylinder head casting (that was new) is bad. They cleaned up the head and installed a new injector tube in the #2 (that had failed) and the injector tube would not seat properly. It went down too far so they ordered a new cylinder head.

New cylinder head should be here this week and they will install.

Should be going again before long.

Mike

New head (cast) warranty? Seems they would of seen this event on first build if they were looking. Sorry your having more delays.
I am still a believer in 71s.

71s rule..

,rc

I agree, but the problem is the rebuild parts went through a phase of very questionable to little quality from 2006 to about 2009. Injectors, heads, pistons, rings, liners, etc....... It seems to hard parts have gotten to be better quality, but there are still some parts out there still on shelves here and there of questionable quality. I had a 12v71TI rebuilt by a DD dealer in 2008 in Ft. Laud. 150hrs and 3 months later it had no compression on 1 cylinder (90lbs).
Another dealer took the motor apart while I watched (Western Branch). 4 of the liners had very strange deep verticle scratches in an area about 1" wide. 5 of the 12 reliabilt injectors were bad, 1 had a split tip. 1 reliabilt head had a chipped valve and bad seat. DD had them take oil and fuel samples 10 days after the motor was dis-assembled trying to get out of warranty. They tried to blame the parts until they realized everything was changed during the first rebuild with reliabilt parts including heads and turbo's. There were no issues with either sample and no water in the fuel. A month later the rebuild was done, DD argued with WB about the bill, $28k for the repairs (not quite another major, but close- main bearings left alone, new head, new injectors, 4 piston kits, check turbo's, etc.) The owner ate $14k so we could pull out and leave to make Chicago and he could have somewhat of a summer with the boat. DD fought him all of the way and never covered the difference.

New cylinder head installed ... all systems go ... sea trial went well. No leaks, fairly clean running. Good to go once more. Time to put the interior back together.

I had one fail on a 12-71, #2 .seems some carbon manged to get up between the injector and the tube causing a split and then hydraulic lock, 12K later...DD did the work and reconditioned the head..if you are lucky and can see some carbon traces at the top of the tube then do the fix right away, we noticed one on the other engine and did the clean up right there, so every year I pull the rocker covers and do an exam to check for any carbon traces. Hopefully can find something prior to a failure.