Cummins M2 300HP 6BTA 5.9

[Norrie1983]

Hello Everyone

I am brand new to this forum having registered only yesterday. I have just concluded on the purchase of my boat which is an Ocean Alexander 390 Flybridge. This boat has twin diesels of the above type and I am hoping that other forum members may be able to tell me how good or bad these engines are, any specific issues to look out for and how expensive is the operation and maintenance.

Hoping someone can help.

Regards
Norrie

 

[Latestarter1]

Hello Everyone

I am brand new to this forum having registered only yesterday. I have just concluded on the purchase of my boat which is an Ocean Alexander 390 Flybridge. This boat has twin diesels of the above type and I am hoping that other forum members may be able to tell me how good or bad these engines are, any specific issues to look out for and how expensive is the operation and maintenance.

Hoping someone can help.

Regards
Norrie

Norrie,

What do you need to know?

Post your engine serial numbers and I can tell you EXACTLY what to watch out for.

Biggest changes took place in 1991 basically very sound motors however we need to pay particular attention to your charge air coolers. Original Cummins M2 300's had welded stainless steel charge coolers with rectangular tubes. Tubes used to 'pant' and fail filling engine with water. Lousy US design, complete pile of dung, wonder how they sent a man to the Moon! Fixed by Cummins engineering team from Darlington who replaced the CAC with a properly engineered design manufactured by Serck in the UK with round tubes, basic design is still in use on current QSB engine.

Once I have your engine serial #s I can tell you what hardware you have and how to turn these into absolutely bomb proof 300 Hp motors.

Good luck

 

[Norrie1983]

Hi

Thanks for your reply!

The limited documentation I have with the boat so far would define the engine numbers as follows:

11573018 and
44573855

Are these the serial numbers that you've requested that will give you the information that you / I need?

Thanks in anticipation of hearing from you

Norrie

 

[Latestarter1]

Norrie,

Dug out a picture of the later style of SWAC (seawater aftercooler) for instant recognition, if you have these you are in good shape.

This is a very good design however like all SWAC coolers requires regular servicing.

Keep an eye out for shaft leaks on the Sherwood raw water pumps, (use ASAP for parts not Cummins Diesel). Genuine Fleetguad filters available just about anywhere aound £5 for lube (LF3349) do not bother with upgrages and £10 for fuel filter. Use decent brand of 15W40 ACEA E5/7 lube, all available from commercial vehicle stockist. Be careful NOT to overfill engines.

When you come up with some engine #'s I can give you a proper update check list.

 

[PCUK]

Cummins engines are the cheapest to rebuild of any commercial engine. That is official not just my opinion. You can buy all your spares including specific marine parts at your local Cummins truck dealer. This engine is used by the US Coastguard. These are basically the best marine engines you could possible buy.

 

[starfire]

Interesting.

Latestarter1, sorry to piggyback on this thread, but I am involved with a 20+ year old SeaRay that has a pair of these, one of the pair is CPL 0970 S/N 445643993.

I wonder if I can presume on you for information on this ?


At the moment this is being rebuilt after raw water ingress into 4 of the 6 cylinders, when things were stripped there was evidence of standing (raw) water in the turbo & exhaust manifold. This had been there since the engine was last run some 6 weeks previous.

There is no evidence of water in the inlet side.

This engine had problems stopping, when shut down the engine would continue to 'rattle' for 10 secs or so, injectors when removed & tested showed a couple dribbling & not shutting off correctly.


Consensus is, the excess fuel was causing the engine to bounce around on compression, rather than continuing to rotate, causing a vacuum in the exhaust manifold & drawing water up from the muffler. Exhaust mixing elbow is sound, muffler is not blocked.

Wonder if you have any further thoughts on this ?

 

[miket]

Fairline Turbo 36

I had a pair of these in my Turbo 36, built 1990.
Strangely, one used to get a discount for this engine option over the more common 306hp VP equivalent once on the 2nd hand market. I would have paid a premium for the Cummins!!
Took me all over the S Coast, Holland, Brittany and C I's without missing a beat.

When I sold the boat, the new owner had fairly major problems after approx' 4 years of his ownership. Not sure what except it was expensive.

I loved them. Good old simple lumps of cast iron.

 

[Latestarter1]

Norrie,

I got your private message.

You posted ESN#s
11573018
44573855

The 11 # is clearly incorrect CPL 970's were build in UK Darlington serial 8 #s starting 21XXXXXX and US Rocky Mount 8 #'s starting 44XXXXXX.

44573855 came up stright away on the database:
6BTA 5.9M(300)
CPL 970
Built Rocky Mount 28th Jan 1991

Assumed that first serial was a typo and substituted 44 fot 11 however came up as not on the database??.

Some good news and some not so good.

#1 You have later Denso fuel pump with boost control. Early 6BTA 300's to CPL 970 used Nippon Denso fuel pump without boost control. 3 and 6 second torque was simply amazing, however as they were using the prop as the LDA, unless propped real light they black smoked like hell.

You do not have that problem. Another issue was that CPL 970's always come out high on power, always had 315 Hp (real not metric hp) just in spec however many were 320Hp and a bit more so needed a bit of taming to get through test. This is another reason why it is imperitive that motors be allowed reach at least 2,800 rpm EGT's climb real quick when engine is pulling over 315 proper Hp.

#2 Unless engine has been uprated and many were, as built you have welded steel after coolers which are designed to fail internally and cause catostropic failure.
Take a look at my picture unless they look like this you have to address the problem.

I will PM with my email address.

 

[Latestarter1]

Interesting.

Latestarter1, sorry to piggyback on this thread, but I am involved with a 20+ year old SeaRay that has a pair of these, one of the pair is CPL 0970 S/N 445643993.

I wonder if I can presume on you for information on this ?


At the moment this is being rebuilt after raw water ingress into 4 of the 6 cylinders, when things were stripped there was evidence of standing (raw) water in the turbo & exhaust manifold. This had been there since the engine was last run some 6 weeks previous.

There is no evidence of water in the inlet side.

This engine had problems stopping, when shut down the engine would continue to 'rattle' for 10 secs or so, injectors when removed & tested showed a couple dribbling & not shutting off correctly.


Consensus is, the excess fuel was causing the engine to bounce around on compression, rather than continuing to rotate, causing a vacuum in the exhaust manifold & drawing water up from the muffler. Exhaust mixing elbow is sound, muffler is not blocked.

Wonder if you have any further thoughts on this ?

No problem, pleased to help if I can.

I will run your esn# when I get a chance.

Unless you can confirm that you have the updated style SWAC's do not even bother lifting a spanner to the engines.

Sea Ray were known to have pretty whacko home brewed exhaust risers, do not think they used the Cummins item. I suspect your basic exhaust design offers little in the way of protection and makes little use of gravity.

'Consensus is, the excess fuel was causing the engine to bounce around on compression, rather than continuing to rotate, causing a vacuum in the exhaust manifold & drawing water up from the muffler.'

Hope that you were not part of the consensus, this king of thinking belongs the know nothing nobhead tech school of convoluted thinking!

If exhaust is working properly there no way that motor can draw water back even if it was able to perform such contortions.

You have three issues.

#1 Two Injectors taken out due to contaminated fuel, all six require rework. (Investigate cause of contamination)

#2 If you have old style SWAC go no further.

#3 Exhaust system potentially not fit for purpose if you have water in the turbo.

#4 If turbo requires replacement use part # from later CPL, costs come out about 50% less than CPL 970 and makes sweeter motor.

I have a guy who rebuilds these old CPL 970 whole nine yards, re-block, later (post 1991) 7mm injector head with K line valve guides rotators, tested on my dyno £4,500 a pop. No VAT.

 

[tinkicker0]

Hello Everyone

I am brand new to this forum having registered only yesterday. I have just concluded on the purchase of my boat which is an Ocean Alexander 390 Flybridge. This boat has twin diesels of the above type and I am hoping that other forum members may be able to tell me how good or bad these engines are, any specific issues to look out for and how expensive is the operation and maintenance.

Hoping someone can help.

Regards
Norrie

Be wise to get your compressions checked IMO, I have found the 6BT cylinder head has major issues with hairline cracking across both the inlet and exhaust valve seats. In automotive applications at least.
Happily they seem to run for years in this state without major troubles, but it can burn a gas path across the valve face causing loss of compression.

 

[Firefly625]

I love reading posts from folk who not only really know their beans....but probably had a hand in designing them... carry on Latestarter1

 

[Latestarter1]

Be wise to get your compressions checked IMO, I have found the 6BT cylinder head has major issues with hairline cracking across both the inlet and exhaust valve seats. In automotive applications at least.
Happily they seem to run for years in this state without major troubles, but it can burn a gas path across the valve face causing loss of compression.

Hey Tinkicker only with 9mm injector head engines and they were replaced with 7 mm 1991 (21 years ago!). Reputable engine rebuilders scrapped off 9mm heads or made use of Cummins ReCon accepting 9mm heads against ReCon 7mm heads for two years after the change over with no bad core surcharge. The bus companies what did they do? Still carried on contracting to rebuilders still using 9mm heads with 7/9mm injector conversion washers regardless.........

Along with 7mm injectors 1991 was also the year when base angine had major upgrade. Block had improved tensile strength torque plate honed during manufacture improving oil control. Torque plus angle cylinder head capscrews revise lube pump, oil cooler and piston cooling nozzles with changed under piston targeting.

At the same time marine applications had water feed to turbo changed from back of cylinder head to back of the block improving the water flow to the exhaust manifold eliminating risk of cracking.

Still run across CPL 970's running a treat, with some huge hours, however they do no have abuse resistance of later post '91' engines. In 2008, the B became the Worlds most sucessful and widely manufacturerd one liter per cylinder engine range.

Found one of the fabricated stainless steel SWAC in the scrap. If you have one of these it HAS to be replaced.

 

[Robin]

I'm very glad our heads were upgraded before we bought our new (to us) boat. I'm doubly glad and trebly grateful for the excellent information on here from Latestarter!

 

[tinkicker0]

Hey Tinkicker only with 9mm injector head engines and they were replaced with 7 mm 1991 (21 years ago!). Reputable engine rebuilders scrapped off 9mm heads or made use of Cummins ReCon accepting 9mm heads against ReCon 7mm heads for two years after the change over with no bad core surcharge. The bus companies what did they do? Still carried on contracting to rebuilders still using 9mm heads with 7/9mm injector conversion washers regardless.........

Along with 7mm injectors 1991 was also the year when base angine had major upgrade. Block had improved tensile strength torque plate honed during manufacture improving oil control. Torque plus angle cylinder head capscrews revise lube pump, oil cooler and piston cooling nozzles with changed under piston targeting.

At the same time marine applications had water feed to turbo changed from back of cylinder head to back of the block improving the water flow to the exhaust manifold eliminating risk of cracking.

Still run across CPL 970's running a treat, with some huge hours, however they do no have abuse resistance of later post '91' engines. In 2008, the B became the Worlds most sucessful and widely manufacturerd one liter per cylinder engine range.

Found one of the fabricated stainless steel SWAC in the scrap. If you have one of these it HAS to be replaced.

Sorry LS, in this case I find myself in the rare position of being in disagreement with you. which knowing what you did for a living is somewhat disconcerting.

It IS the 7mm head I am talking about, indeed I have never actually seen a 9mm head but am aware of them and I have seen the copper top hat injector nozzle sleeves you mention in the gasket kits. To be double sure - the head I am talking about has the top hat type stem seals that double as spring seating washers.
Most of these motors are around 10 years old and certainly not 21!

Torque and angle bolts - check.
Longer piston cooling jets - check.
Fracture rods instead of machined - check.

I have around a 60% rejection rate for 6BT heads due to hairline cracks developing in the valve seats - NOT the head casting and since it is cheaper to fit new heads than have the guides, valves and seats reworked, they go in the scrap area to sent wherever as old core.
Often the cracks are not noticeable at first glance so our standard method to determine whether the head is suitable for further attention is to spin up the valves with a bit of fine grinding paste. A good inspection with a strong worklight will then reveal them. I have come across heads with 12 out of 12 seats cracked.

As said before, this does not seem to be a particular concern to the motor and they seem to run happily in this state without issue other than cutting a very occasional gas channel in the valve face, but there is no way I am refitting a head with cracked seats.

Sorry to be the bearer of bad tidings LS


EDIT: Not to alarm other forumites unduly, perhaps I should mention that the motors I get to recondition have already done a gazillion hours and are exceptionally hard worked.

 

[Latestarter1]

Sorry LS, in this case I find myself in the rare position of being in disagreement with you. which knowing what you did for a living is somewhat disconcerting.

It IS the 7mm head I am talking about, indeed I have never actually seen a 9mm head but am aware of them and I have seen the copper top hat injector nozzle sleeves you mention in the gasket kits. To be double sure - the head I am talking about has the top hat type stem seals that double as spring seating washers.
Most of these motors are around 10 years old and certainly not 21!

Torque and angle bolts - check.
Longer piston cooling jets - check.
Fracture rods instead of machined - check.

I have around a 60% rejection rate for 6BT heads due to hairline cracks developing in the valve seats - NOT the head casting and since it is cheaper to fit new heads than have the guides, valves and seats reworked, they go in the scrap area to sent wherever as old core.
Often the cracks are not noticeable at first glance so our standard method to determine whether the head is suitable for further attention is to spin up the valves with a bit of fine grinding paste. A good inspection with a strong worklight will then reveal them. I have come across heads with 12 out of 12 seats cracked.

As said before, this does not seem to be a particular concern to the motor and they seem to run happily in this state without issue other than cutting a very occasional gas channel in the valve face, but there is no way I am refitting a head with cracked seats.

Sorry to be the bearer of bad tidings LS


EDIT: Not to alarm other forumites unduly, perhaps I should mention that the motors I get to recondition have already done a gazillion hours and are exceptionally hard worked.

Tinkicker Forumites have zero cause for alarm anyway. After mid 1991 ALL marine and certain constant speed B CPL's fitted with premium cylinder heads. Upgraded valve guides high temperature valves and seats. Plus valve rotators on both inlet and exhaust.

As to being bearer of bad tidings, that is the message I generally bring to your bus operators. The issue you speak of is not a base engine issue but one of muppet maintenance.
Dug into my black museum here is extract.........

Cummins Diesel ReCon 6BT Part # 4960RX built Cumbernauld Oct 2001 and fitted in Dennis Dart SLF December 2001. Bus decomissioned July 2009 due at internal accident. Engine deemed to be in running order at time of accident and fit for further use. Engine had accrued 23,300 hours before bus removed from service.

Oil drains had been carried out annually using correct lubricant and Fleetguard filters, something like 3,000 hr (reputed) lube oil drains.

Upon tear down oil pan had to be removed to drain lube as drain plug was expoxied in place due to partially stripped thread. Bottom of oil pan was 15mm deep in solid sludge and debris. Air compressor had been replaced, capscrews low break off torque and brace missing. Front timing gear showed signs of fretting against block most likely due poor fitting of replacement compressor. Cam lobe spalled on four out out of five exhaust lobes. Tappet faces also showed signs of distress. Balls in the ends of the push tubes severely worn out of round and actually drilling into tappets (Mitsubishi push tubes are normally bomb proof). Valve tips and rocker pads showing signs of distress. One exhaust valve seat cracked.

Conclusion: There was NO evidence in the records that overhead had ever been adjusted during the life of the engine 23,300 hours, the exhaust valve seat cracking was clearly due incorrect valve clearance due to lack of setting in service and severe wear in the valve train caused by 3,000hr + lube oil drains, resulting severe valve 'beat in' and seat failure.

As the drain plug had been epoxied in I had my doubts that lube had been drained at 3,000 hrs. The front oil seal was leaking due to fishing line probably picked up from the road being wound around the damper and damaging the oil seal. The oil leak required regular lube oil top ups which I suspect were replenishing the additive in the lube oil giving it some level of respite.

Suspect these little donks do a sterling job in the face of much adversity.......

PS I have suggested to bus companies that they may want to specify marine heads at a £500 premium. Silence was deafening.

Amazing thing is that bus servicing is of far higher standard in Zimbabwe than the U.K

 

[tinkicker0]

Tinkicker Forumites have zero cause for alarm anyway. After mid 1991 ALL marine and certain constant speed B CPL's fitted with premium cylinder heads. Upgraded valve guides high temperature valves and seats. Plus valve rotators on both inlet and exhaust.

As to being bearer of bad tidings, that is the message I generally bring to your bus operators. The issue you speak of is not a base engine issue but one of muppet maintenance.
Dug into my black museum here is extract.........

Cummins Diesel ReCon 6BT Part # 4960RX built Cumbernauld Oct 2001 and fitted in Dennis Dart SLF December 2001. Bus decomissioned July 2009 due at internal accident. Engine deemed to be in running order at time of accident and fit for further use. Engine had accrued 23,300 hours before bus removed from service.

Oil drains had been carried out annually using correct lubricant and Fleetguard filters, something like 3,000 hr (reputed) lube oil drains.

Upon tear down oil pan had to be removed to drain lube as drain plug was expoxied in place due to partially stripped thread. Bottom of oil pan was 15mm deep in solid sludge and debris. Air compressor had been replaced, capscrews low break off torque and brace missing. Front timing gear showed signs of fretting against block most likely due poor fitting of replacement compressor. Cam lobe spalled on four out out of five exhaust lobes. Tappet faces also showed signs of distress. Balls in the ends of the push tubes severely worn out of round and actually drilling into tappets (Mitsubishi push tubes are normally bomb proof). Valve tips and rocker pads showing signs of distress. One exhaust valve seat cracked.

Conclusion: There was NO evidence in the records that overhead had ever been adjusted during the life of the engine 23,300 hours, the exhaust valve seat cracking was clearly due incorrect valve clearance due to lack of setting in service and severe wear in the valve train caused by 3,000hr + lube oil drains, resulting severe valve 'beat in' and seat failure.

As the drain plug had been epoxied in I had my doubts that lube had been drained at 3,000 hrs. The front oil seal was leaking due to fishing line probably picked up from the road being wound around the damper and damaging the oil seal. The oil leak required regular lube oil top ups which I suspect were replenishing the additive in the lube oil giving it some level of respite.

Suspect these little donks do a sterling job in the face of much adversity.......

PS I have suggested to bus companies that they may want to specify marine heads at a £500 premium. Silence was deafening.

Amazing thing is that bus servicing is of far higher standard in Zimbabwe than the U.K

Pretty much what I find and can agree about bus company "fitters". However I can't complain because it keeps a roof over my head.

Re the epoxied in drain plug. Of course you know standard bus garage practice in such a case is to remove the filter, put a bucket under and let it idle until the oil stops gushing. Or so i have been told.

Cams as already mentioned via PM are always cream crackered as are the tappets whether it be the 6BT, ISB or ISC.
Exhaust valve rockers always require replacement as do the valves for the reasons you mentioned.
Not forgetting of course the fretting on the timing case and cracked injector pipes where someone has left the injector pump bracket off, the thing has compressed its gasket, come adrift and is dancing around on the kidney slots.

Don't get me started on rusted blocks and cavitation damage to liners because they have been topping them up with clean water (ISC)

Whether the heads usually go bad or not, I just tell it as I find it

Just glad we only offer a 12 month warranty.

 

[Latestarter1]

Whether the heads usually go bad or not, I just tell it as I find it

Just glad we only offer a 12 month warranty.

In 1992 Mr Komatsu say you fix engine real good now with new cylinder head, we cannot break it, werelly like little engine now but too noisy, we help you fixee. Hence STORM block and ladder frame, just to make life near impossible to work on underneath when installed in a vehicle!

I was involved with the CVR(T) repower project replacing over 2,000 Jaguar engines in the Scimitar and other members of the familiy. Certain people in the MOD wanted a motor with less torque to save spending money on new gearbox. B was first four stroke to pass the US Navy 500hr endurance test.
Despite US Navy test data MOD wanted to to do their own endurance cycle which included series of tests including running chilled coolant into the engine whilst it was pulling peak torque on the dyno, plain crazy! Three makes of engine were shortlisted, Brand A failed a head gasket at 300 hrs so tests had to be run over again, then Brand C picked up a piston at about 400 hours. MOD ran third set of tests and Brand C supplied new engine which picked up piston at just over 200 hours of testing. Little B said have I got the job yet, getting tired of all this pain. MOD selected the B and forced to revamp the gearbox, making a far better vehicle overall.

Tinkicker bite the bullet fit a marine head, I will PM the part # then offer two year warranty!

 

[starfire]

'Consensus is, the excess fuel was causing the engine to bounce around on compression, rather than continuing to rotate, causing a vacuum in the exhaust manifold & drawing water up from the muffler.'

Hope that you were not part of the consensus, this king of thinking belongs the know nothing nobhead tech school of convoluted thinking!


You have three issues.

#1 Two Injectors taken out due to contaminated fuel, all six require rework. (Investigate cause of contamination)

#2 If you have old style SWAC go no further.

#3 Exhaust system potentially not fit for purpose if you have water in the turbo.

#4 If turbo requires replacement use part # from later CPL, costs come out about 50% less than CPL 970 and makes sweeter motor.

No, not part of the concensus, but, no evidence of water, at all, in the inlet side of things, however the swac is the old style, I will pass your comments onto the owner.

This setup has been fine for 20+ years, what would cause raw water to rise to the level of the turbo and exhaust manifold is the puzzling bit.

The water side of the turbo, manifold & exhaust elbow have been pressure tested & are Ok.

Fuel & filters are clean, but, I suspect the injectors have not been touched since the engine was built, all 6 have now been reworked.

The exhaust riser is the cummins part, but with sea ray exhaust plumbing, there is no siphon break & no easy way of getting one to the required height above the injection point into the elbow.


Many Thanks,

 

[Latestarter1]

No, not part of the concensus, but, no evidence of water, at all, in the inlet side of things, however the swac is the old style, I will pass your comments onto the owner.

This setup has been fine for 20+ years, what would cause raw water to rise to the level of the turbo and exhaust manifold is the puzzling bit.

The water side of the turbo, manifold & exhaust elbow have been pressure tested & are Ok.

Fuel & filters are clean, but, I suspect the injectors have not been touched since the engine was built, all 6 have now been reworked.

The exhaust riser is the cummins part, but with sea ray exhaust plumbing, there is no siphon break & no easy way of getting one to the required height above the injection point into the elbow.


Many Thanks,

You mention syphon break some Sea Rays had Vernatone water lift, check out dimensions some installations live on the edge then one day.............


Good luck

 

[FRODRIGUEZ]

Dear Sir
I am wondering if you could help me answering a similar question as Norri? I have a Jeantot 42 power cat with two 300 HP cummins 6bta 5.9 1995. I am not able to see the engine serial number and I wonder if you could direct me to where to look for.
Thank you so much