Engine Survey for DD 6V92s

[Capt. Kirk]

I have an accepted off on a RPHMY with twin 550 HP DD 6V92s.
With 550 HP, am I correct that they must be TAs?
The current owner has had her for five years. He says he has run her at 8 to 10 knots, occasionally 20 knots.
Of course, I don’t know the entire history of usage, so I plan to hire an experienced Detroit engine surveyor, if I can get one – it seems there are only two on the Chesapeake and one doesn’t return phone calls.
I will ask the engine surveyor to not pull any punches, submit an oil sample, and review the rebuild documentation from the owner.
I have one quote for a “basic survey” of $1800 to $2200 for a full day, including travel. Is that a fair amount?
I asked about having them take a deeper dive and they said they could remove the valve covers and do a bore scope. They said that would be a second day at the same rate
Should I plan to do this? Is it needed? Should I plan it in advance or wait until they’ve done the first day, “basic survey” first?
Is there anything else I can or should do?

 

[Lepke]

Yes, TAs. Rebuilding cost for one engine is much more than a 2 day survey on both. If the 2nd uncovers a problem, then it was worth it. If it doesn't, you have peace of mind.
If you use the engines at 80% or less hp, they will last at least twice as many hours between overhauls. Keep the oil clean, maybe triple the hours. Think about adding a good bypass oil filter.
If you're handy, learn to do the maintenance. It's not rocket science. It's better to do it yourself than trust the usual marina mechanic with a Detroit.

 

[FF]

"I have one quote for a “basic survey” of $1800 to $2200 for a full day, including travel. Is that a fair amount?"

The problem with a DD is to check the compression the injectors must be removed.

The big hassle is after putting them back in place they have to "run the rack',, it takes a good while to adjust the injectors so all are timed properly , so all the cylinders will do equal work. You hopefully are paying for the installers skill set for this task.If the compression is good , adjust the valves too.

Since DD can be rebuilt in place some folks will take the risk and simply do a smoke check.

The technique requires a totally cold engine , at least a day of no operation.
It takes a long time for more than a ton of iron to get room temperature,in a closed engine room.

Remove all the dock hoses power line and single up the dock lines.

Start the engine and quickly ( 30 seconds or so) get underway at modest 700-800 rpm.Observe the smoke coming out the exhaust, as the engine warms , increase the rpm.

The temperature at which the white (incomplete compression) smoke clears is a reasonable sign of the cylinder state , Clean at 120F its a great engine, 140F normal mid life , OK to cruise but no sport fish full throttle ,180f , the engine is needing at least an inframe , although if not run hard may still have another 1000 hours to go.

The engine must be under load to warm up normally , dockside wont do.

For folks without thousands of survey bucks its at least a rough idea of engine condition,
or will give an idea of if its worth a survey.

 

[Capt. Kirk]

"I have one quote for a “basic survey” of $1800 to $2200 for a full day, including travel. Is that a fair amount?"

The problem with a DD is to check the compression the injectors must be removed.

The big hassle is after putting them back in place they have to "run the rack',, it takes a good while to adjust the injectors so all are timed properly , so all the cylinders will do equal work. You hopefully are paying for the installers skill set for this task.If the compression is good , adjust the valves too.

Since DD can be rebuilt in place some folks will take the risk and simply do a smoke check.

The technique requires a totally cold engine , at least a day of no operation.
It takes a long time for more than a ton of iron to get room temperature,in a closed engine room.

Remove all the dock hoses power line and single up the dock lines.

Start the engine and quickly ( 30 seconds or so) get underway at modest 700-800 rpm.Observe the smoke coming out the exhaust, as the engine warms , increase the rpm.

The temperature at which the white (incomplete compression) smoke clears is a reasonable sign of the cylinder state , Clean at 120F its a great engine, 140F normal mid life , OK to cruise but no sport fish full throttle ,180f , the engine is needing at least an inframe , although if not run hard may still have another 1000 hours to go.

The engine must be under load to warm up normally , dockside wont do.

For folks without thousands of survey bucks its at least a rough idea of engine condition,
or will give an idea of if its worth a survey.

Sorry, but I'm confused.

Are you suggesting I do all the following for my engine survey?

Remove the injectors to check the compression? And then put them back in and "run the rack?"
"Adjust the injectors so all are timed properly , so all the cylinders will do equal work? And adjust the valves too?

Please advise.

 

[STB]

I've never owned Detroits. I did make an offer on a boat with
them once but it fell through, I don't remember why.

But, if I were the seller and someone suggested they have mechanic do all of that disassembly and reassembly on my engines, I'd tell them to by a different boat.

The exceptions would be (a) if it were in response to some type of finding, e.g. abnormal smoke or slow start, or (b) if I, personally, knew the mechanic well, even if just by reputation.

There are just too many buyers to have some potential buyer's broker's tool screw up my rack, etc.

If the engine starts fast, hunts only briefly, smokes normally and cleans up normally, runs up to rpm without excessive black smoke, doesn't look burned up at the exhaust manifold, looks good at the elbow, hoses, and coolers, has good pressure and temp, and has a good engine oil analysis, I'm not sure what one would be looking for.

Invasive diagnostics are best to identify a problem, but, like too much medicine, can only cause one if there isn't one.

I think.

 

[gsholz]

I'd not pay for an invasive survey. A good indicator of DD health is a real cold start. Make sure the engine has not been started that day. Start it around 45-50 deg F. If the engine starts quickly (cranking just a few seconds) and if the white smoke (unburned fuel) goes away within 30 seconds, the engines have good compression indicating limited wear.

If you need to crank excessively or white smoke persists, the engines show lack of compression usually caused by wear. You should then price in new kits.

 

[sean9c]

I'd a 6v53 that was that way. Stone cold it pretty much wouldn't start without either cranking it long enough that friction would build a little heat up or you used ether. Once it started that first time you could let it sit for hours hit the key and it'd start immediately.
When I bought the boat, unfortunately, the seller also knew this, and without us knowing would show up early on the days of sea trial and survey and make sure that the engine had a little heat in it.

I'd not pay for an invasive survey. A good indicator of DD health is a real cold start. Make sure the engine has not been started that day. Start it around 45-50 deg F. If the engine starts quickly (cranking just a few seconds) and if the white smoke (unburned fuel) goes away within 30 seconds, the engines have good compression indicating limited wear.

If you need to crank excessively or white smoke persists, the engines show lack of compression usually caused by wear. You should then price in new kits.

 

[Taras]

If they are "DDEC's" (detroit diesel electronic control), then be careful........ a friend of mine has 6V92 DDEC's and its been a constant struggle to keep them running. Lots of electronic "issues" that has resulted in a lot of money being spent

 

[Ken E.]

I'd not pay for an invasive survey. A good indicator of DD health is a real cold start. Make sure the engine has not been started that day. Start it around 45-50 deg F. If the engine starts quickly (cranking just a few seconds) and if the white smoke (unburned fuel) goes away within 30 seconds, the engines have good compression indicating limited wear.

If you need to crank excessively or white smoke persists, the engines show lack of compression usually caused by wear. You should then price in new kits.

I concur with this comment, and formerly owned DD 871's. A cold start is a good test, watching the smoke as described above. Then a sea trial, watching for smoke -there shouldn't be any. Then run it up to WOT to see if it will come up to rated rpm and keep it there, watching water temps and noting any vibrations. If no faults appear, I'd be feeling pretty good about the engines in a general sense.

 

[FF]

Remove the injectors to check the compression? And then put them back in and "run the rack?"
"Adjust the injectors so all are timed properly , so all the cylinders will do equal work? And adjust the valves too?

If you want to check the compression , this is the way it is done.

On "other" injection setups the timing is done in the pump , and the injector just squirts.

On a DD the injector has a cam lobe that pushes down on the injector , as each injector is its pump it must be timed to the other cylinders.A simple procedure , but does require some skill.

DD did this so the injector size could be matched to the desired engine power out put.

 

[AlanT]

I have an accepted off on a RPHMY with twin 550 HP DD 6V92s.
With 550 HP, am I correct that they must be TAs?
The current owner has had her for five years. He says he has run her at 8 to 10 knots, occasionally 20 knots.
Of course, I don’t know the entire history of usage, so I plan to hire an experienced Detroit engine surveyor, if I can get one – it seems there are only two on the Chesapeake and one doesn’t return phone calls.
I will ask the engine surveyor to not pull any punches, submit an oil sample, and review the rebuild documentation from the owner.
I have one quote for a “basic survey” of $1800 to $2200 for a full day, including travel. Is that a fair amount?
I asked about having them take a deeper dive and they said they could remove the valve covers and do a bore scope. They said that would be a second day at the same rate
Should I plan to do this? Is it needed? Should I plan it in advance or wait until they’ve done the first day, “basic survey” first?
Is there anything else I can or should do?

Last year I bought a boat with 8V92TA's. My Diesel Mechanic saved me $68k. At sea trial he asked sellers broker to run the boat up to WOT. At WOT the temperature of one engine immediately went into the red amidst an explosion of steam and fluid. We shut down the engine. Later analysis shows we had cylinder and piston damage. Seller wound up having to rebuild the entire engine. (New pistons, liners, cylinder heads). It was determined that engines had received no maintenance for 4+ years and the cooling system was severely compromised on both engines, It worked at slow cruising speed but was immediately and destructively inadequate at WOT. We were able to get seller to pay to have our mechanic rebuild the engine and also the cooling system on the other engine in order to close the sale.

These engines both passed the "cold start" test described by others. If my mechanic had not insisted we run the WOT test that would have been my $68k!

 

[sbman]

I have an accepted off on a RPHMY with twin 550 HP DD 6V92s.
With 550 HP, am I correct that they must be TAs?
The current owner has had her for five years. He says he has run her at 8 to 10 knots, occasionally 20 knots.
Of course, I don’t know the entire history of usage, so I plan to hire an experienced Detroit engine surveyor, if I can get one – it seems there are only two on the Chesapeake and one doesn’t return phone calls.
I will ask the engine surveyor to not pull any punches, submit an oil sample, and review the rebuild documentation from the owner.
I have one quote for a “basic survey” of $1800 to $2200 for a full day, including travel. Is that a fair amount?
I asked about having them take a deeper dive and they said they could remove the valve covers and do a bore scope. They said that would be a second day at the same rate
Should I plan to do this? Is it needed? Should I plan it in advance or wait until they’ve done the first day, “basic survey” first?
Is there anything else I can or should do?

That's a big red flag to me on the mechanic's part.

Exactly how would they do a 'borescope' after removing the valve covers? A DD does not have any holes in the cylinder top from which to do a borescope, only injector removal would be enough to do this and this (as everyone has pointed out) requires re-doing the rack adjustment after re-installing the injectors. Not to mention potential for creating fuel tube leaks.

But then you have to ask yourself WHY IN THE WORLD would you do a borescope on a DD? Just take the airbox covers off the side of the block and you can see right into the cylinders and 'borescope' all you want from there. If the person suggesting this operation was the actual person that is going to do the work, then I would suggest finding someone else. If it was just office staff suggesting 'the usual' that's a different story I wouldn't expect them to know the difference.

 

[sbman]

Also, the 92 series V motors tend to have main bearing wear that requires periodic replacement of the main bearings, especially if run under heavy loads. If there is no documentation of this having been done, you might expect to be doing this as preventative maintenance yourself and find out how much your mechanic would charge to do so. It can be done in-place as long as there is room to work under the engine.

 

[Capt. Kirk]

That's a big red flag to me on the mechanic's part.

Exactly how would they do a 'borescope' after removing the valve covers? A DD does not have any holes in the cylinder top from which to do a borescope, only injector removal would be enough to do this and this (as everyone has pointed out) requires re-doing the rack adjustment after re-installing the injectors. Not to mention potential for creating fuel tube leaks.

But then you have to ask yourself WHY IN THE WORLD would you do a borescope on a DD? Just take the airbox covers off the side of the block and you can see right into the cylinders and 'borescope' all you want from there. If the person suggesting this operation was the actual person that is going to do the work, then I would suggest finding someone else. If it was just office staff suggesting 'the usual' that's a different story I wouldn't expect them to know the difference.

It was someone in the office not a mecahnic, but still surprised they would say that if they really didn't know how this works. Thanks for the insight.

 

[PacificBlue]

We always did this on all boat purchases with Diesel engines:

Borescope liners to check for scuff marks on cylinder bore surfaces.

Leak down or compression test on each cylinder.

Oil analysis.

You only get one chance before you become the owner. All good money spent.

Moist people neglect the gearbox, it deserves a look as well.

Once we bought each boat, all engine and gear hoses replaced with enough additional onboard spares. I like to start at a comfortable baseline when I get a new to me used boat.

 

[Ski in NC]

I do these in two steps: First is visual inspection and cold start. You can look at three holes on the 692 550 through right bank air box covers. Usually the left bank covers are occluded by coolant piping, starter, etc. I look at what I can access. Then sea trial and check all the temps and pressures. Second step comes into play if problems are found on step 1.

If engine starts well and has minimal smoke (depending on outside/engine temp)and sea trial numbers are all good, often I tell the buyer that the compression is at least above spec. I can go to step two and do a comp test, but based on the smoke it is above minimum an it really will not tell you anything.

I have tried borescopes, but the image you see mostly creates more questions than it resolves. And you can not see piston rings with a borescope.

I have never found a low compression hole on a DD that did not already have symptoms. I knew the engine was sick before the tester went in the hole.

 

[ronobrien]

I have an accepted off on a RPHMY with twin 550 HP DD 6V92s.
With 550 HP, am I correct that they must be TAs?
The current owner has had her for five years. He says he has run her at 8 to 10 knots, occasionally 20 knots.
Of course, I don’t know the entire history of usage, so I plan to hire an experienced Detroit engine surveyor, if I can get one – it seems there are only two on the Chesapeake and one doesn’t return phone calls.
I will ask the engine surveyor to not pull any punches, submit an oil sample, and review the rebuild documentation from the owner.
I have one quote for a “basic survey” of $1800 to $2200 for a full day, including travel. Is that a fair amount?
I asked about having them take a deeper dive and they said they could remove the valve covers and do a bore scope. They said that would be a second day at the same rate
Should I plan to do this? Is it needed? Should I plan it in advance or wait until they’ve done the first day, “basic survey” first?
Is there anything else I can or should do?

First to my knowledge "TA" refers to turbocharged & after cooled (induction air cooled by engine coolant). I don't get your Q that they must be TA, but maybe I am missing something. If the proposal is to use a bore scope, I would think they could remove the blower box covers and scope up into the cylinders there. That seems easier to me than going in through the top. Just some thoughts. Best of luck. PS Detroits run forever.

 

[MYTraveler]

I don't think you need the mechanic for a full day. As far as checking compression, IME (twin 892s, which I had rebuilt twice, and talking with lots of owners and mechanics when I owned them), if they have a compression problem that will show up when you start them cold (make sure the boat has not been run for 24 hours before you get there. If they engines are warm, the seller is hiding something). There are easily removable plates on the side of the engine that allow borescope access through the ports into the cylinders. The most important thing is how clean the exhaust is (black or blue smoke is bad to very bad, brown haze is typical, white that quickly dissipates is steam), how stable the engine and exhaust gas temps, and oil pressures, and that it makes rated rpm. A good mechanic can tell a lot just by listening to the engines. As important as the engines, are the gears, especially if they are Alisons. The gear pressure should be consistent and set to whatever the spec is (350 psi?). Too little pressure and the gears will slip (resulting in dirty, smelly gear oil), too much pressure and they will blow out the rear main seal.

 

[dwiggl]

I bet one of those 2 surveyors on the Chesapeake is named Tom Hug. He did a very thorough survey on my 6-71's and was spot on with the work that needed to be performed to bring the units up to optimal. Very professional survey documentation, and he spent an hour going over all of the issues. This was a huge help to the technician that ultimately did the work.
Not cheap and money well spent.
Unfortunately he does not do a good job around answering the phone or retuning calls. He seems to just disappear when he gets busy. In speaking with others that just seems to be his MO. But that seems to be the way these days with the shortage of experts in the industry these days.
If you can find him - use him.

 

[AlanT]

Just a quick note to make sure when requiring the seller to allow you a cold start, is to mention that any pre-heaters are also turned off at least a day before. When you turn on the ignition on the DDEC displays it will show the temperature of the engines (before you start them). This temperature should be ambient. If it is higher then either the engine has been run or the pre-heaters were on. ~A