QSC 500's vs. 6CTA engines

[ezwoo]

I'm looking at 42-44 Sedan bridges '04 to '06. The brokers don't seem to know much about the difference in these engines. I was optimistic that I could get some opinions about the pro's and con's of each on this board. I took these numbers right off of the listings, if they are not right. Thanks.

 

[Robski97]

The short version is the QSC are fully electronic. NO SMOKE , very little smell. GREAT MOTORS. The 6CTA's are mechanical motors and smoke....

Frank and the guys can fill in more but QSC if possible are the way to go....

Rob

 

[fwebster]

I believe the rotating assemblies are about the same on both motors and both are based on the old C-series design which is a proven, sound engine. The major difference is the fuel delivery system and the head/valve design.

The QSC is an electronic common rail high pressure fuel system. That affords more precise fuel delivery, and as Rob mentions, the QSC engines have less smoke and more complete combustion when cold. The new head design has 4 valves per cylinder and results in quicker acceleration and higher HP ratings, although the HP increase probably comes from higher rpms. The QSC is still relatively new and some minor issues are surfacing........most notably the high pressure fuel line is prone to vibration which can crak the fittings thus causing a high pressure fuel leak, the accessory drive belt and idler system is prone to throwing off the belt when it gets a little wear a little and stretches (carry spare belts, learn to change them and do it while at the dock since they can be difficult to access on some models.) The engine control computers seem to be causing some problems, Out of 10 44DB,'s 44DA's and 48DA's in our dealer owned marina, all but 2 have had faulty starting and frequent limp mode problems.

The 6CTA is a proven work horse. They require an intake chamber heater to aid in cold start/smoke. Most of these engines whose owners complain about smoke, have either faulty heaters or the heaters were never hooked up from the factory. The 6CTA is a very dependable engine that is also very easy to maintain.

I am sort of an old school guy and personally, I prefer older design mechanical engines like the 6CTA. When you are 75 miles off shore, there is just less to go wrong with mechanical engines than with new electronic engines. Having said that, having QSC's instead of 6CTA's would not keep me from buying the right boat and I certainly would not pass on a boat because it had one engine instead of the other.

Hope that helps.

 

[Skip]

I have 6CTAs in my 03 420DA. I have put 520 hours on the engines since I bought the boat. My average fuel usage year over year is 21.5 GPH, and the oil samples since 2006 show the engines are holding up quite well.


All I have ever had to do beyond normal annual maintenance (fluids, filters, anodes) is to change thermostats when I bought the boat, probably due to the fact that the boat sat for a year before we bought it. The nice thing about the 6CTAs is that I can do nearly all the maintenance myself.

At Fwebster's suggestion I use a product called power service diesel kleen which compensates for the reduced lubricity in ULSD fuel. This product also boosts cetane.

My engines don't smoke much at start up. They do, however, smoke more than the QSC 500s in my friend's 44DB.

When we sea trialed the boat the Cummins tech discovered that the intake chamber heaters had not been installed properly. When properly functioning, these cut down on the smoking at cold start.

I'd guess there are very few 04 420DBs with 6CTAs. By late 2004 Cummins was building the 480CE. The QSC 500 followed in the 06 model year, I believe.

 

[Jaws]

I have the 6CTA's as well and find them to be reliable. Start up produces very little smoke except on the coolest of Michigan mornings. However they will smoke on a cold start if you advance the throttles to a faster idle. In cooler climates you either let the intake heaters do their job or install the Wolverine pan heaters as I am doing over the winter.
The only problem that I have had thus far with the mechanical motors is a starter relay that has twice failed me. It is very easy however to do an emergency start by laying a screwdriver across the terminals. Otherwise they are problem free if maintained.

 

[Converse48]

I have the QSCs in my 44DB. A buddy has the 480CEs in a 2003 400DB. I'm not sure how the 6CTA differs from the CE, but the 420/44DB will have either 480CE or QSCs in it. Both boats run strong. Mine smokes less at start up, and at all times, and is smoother in terms of noticeable vibration. The QSC-powered boat also accelerates much faster and runs a bit faster, although only a couple of knots.

As Frank mentioned, there was a recall on the QSC to install a bracket to keep the high pressure fuel line from vibrating and cracking. Mine was one of the lucky ones that cracked. Sprayed fuel everywhere. Both have been "fixed" now for three years and we've had no problems.

I can do all of the "routine" preventative maintenance on my engines. Anything involving the fuel delivery system, other than filters, is off limits for amateurs. But I have never had any problems (knock wood) beyond the one fuel line.

With the QSC, they eliminated the coolant filter and made some things easier to get to. Changing impellers on both is a pain in the a$$.

As far as fuel consumption, I'm gathering that the QSC is a little less efficient... it's hard to tell because the CE doesn't have fuel flow meters so we have to go with "averages" which are virtually meaningless. However, given that my buddy and I run together most times, a comparison from his boat to mine is reasonable. He "averages" 22 across a season and I "average" 23 GPH. Given that my boat is slightly faster it's probably close to a wash on a NMPG basis. But I will give a very slight nod to the CE on efficiency. I'm not a fan of "averages" because my fuel flow shows 40GPH at cruise, yet I "average" 23 in actual consumption. I have seen people compare their "averages" to real-time fuel flow meters to argue that their boats are more efficient than others...

I appreciate Frank's point about ease of self maintenance. But neither me or my buddy are the types that are going to adjusting the valve lash or injector timing ourselves. We do all the routine preventative maintenance ourselves, but everything major is left to pros anyway. In three years of side-by-side running and maintenance, there has never been anything he could do on his boat that I couldn't on mine. Arguably, routine maintenance is easier on the QSC.

So, all that said, I strongly prefer the QSC-powered boat. Stronger, faster, quieter, cleaner and smarter (i.e. Smart Craft) works for me. But take all that with a grain of salt. I doubt anyone is going to weigh in that they think "the other" motor is better.

 

[jrirvine1]

I run the 480CE 6CTA (C series, electronic fuel delivery, 6 cylinder, turbocharged and after cooled) I have put about 230 hours on since purchasing the boat and find the Cummins to be great engines with my numbers mostly like Skip’s. The only issue is that both alternators needed to be replaced within about 80 hours of each other, or around 600 hours. Some have speculated that this is the weak link on these engines and the alternator failure may due to the heaters cycling at start up. This voltage draw can be seen in the gauge at the helm and is a normal condition for these engines.

We have never felt the boat was underpowered and have had no problems keeping up and cruising with other boats. Mine smoked a bit the first season, mostly in the fall when the air was cooler. This was remedied by finally understanding what every more experienced diesel dude told me. That is, the three most important requirements for a diesel is – Clean, Clean and Clean. (Clean air, clean fuel and clean filters.)

Yes, my engines are better.

 

[fwebster]

Tim,

I take it you have yet to experience having to hit the starter button 15 times to get the engine to crank........only to have Cummins tell you it isn't their problem and the Sea Ray dealer tell you it isn't a switch problem? When it does happen, cut to the chase and tell the Cummins guy to bring an engine control computer with him and plan to change it.

or, idling home in limp mode........from 75 miles off-shore? Its a sensor, but which one and do you have spare?

or, having the systems monitor scream an overheat warning to you at the worst possible time in a crowded waterway, only to find that one serpentine belt has been thrown off the idler and is wadded up in the bilge.

Cummins' pattern is to not fix systemic problems such as those above until a customer complains........like Animal House, sort of a double secret warranty recall. I hope you don't have to deal with any of the above, but there are a lot of QSC owners who have.

 

[Converse48]

Tim,

I take it you have yet to experience having to hit the starter button 15 times to get the engine to crank........only to have Cummins tell you it isn't their problem and the Sea Ray dealer tell you it isn't a switch problem? When it does happen, cut to the chase and tell the Cummins guy to bring an engine control computer with him and plan to change it.

or, idling home in limp mode........from 75 miles off-shore? Its a sensor, but which one and do you have spare?

or, having the systems monitor scream an overheat warning to you at the worst possible time in a crowded waterway, only to find that one serpentine belt has been thrown off the idler and is wadded up in the bilge.

Cummins' pattern is to not fix systemic problems such as those above until a customer complains........like Animal House, sort of a double secret warranty recall. I hope you don't have to deal with any of the above, but there are a lot of QSC owners who have.

No, I have not had any of these experiences, but you're making me nervous.

Just decided to do a preemptive strike on the serpentine belt. I do have the spares, so it's time to use 'em.

 

[Boatingfool]

I doubt anyone is going to weigh in that they think "the other" motor is better.

I agree, both engines are very similar and very stout. I had the 450hp mechanical versions in my last boat. At 1,400hrs they never missed a beat...and extremely efficienct. Little smokey while cold, but many people did the 480 CE version injector upgrade which curbed the smokey cold startup (I had purchased the injectors but sold the boat before I got around to changing them).

Very easy motors to maintain and inexpensive shal anything need replacing. I do believe the later veriants have sleeves...so if you rack up 3000hrs it would be easier to rebuild.

 

[ezwoo]

Thanks all for the input. As usual, the information came fast and furiously. CSR is a remarkable resource that adds vakue to my Sea Ray.

 

[Robski97]

WE havent had the experiences Franks posts about with the QSC's but his super secret recall did come up . Back in 06 I had an injector issue . Today there on the boat replacing all my injectors on both motors. So you might want to inquire.... Last thing u want is a hung injector....

Rob

 

[Converse48]

Who are "they"? And did "they" call you, or did you call them?

 

[Robski97]

Sorry, They = local Cummins guy. I called them to schedule my aftercooler maint and Valve lash Adj. They stated they would be replacing all my injectors. ( both motors ) No doubt if I didnt call it would not have been done .

Rob

 

[bmac]

Sorry, They = local Cummins guy. I called them to schedule my aftercooler maint and Valve lash Adj. They stated they would be replacing all my injectors. ( both motors ) No doubt if I didnt call it would not have been done .

Rob

Rob

We need to talk. I've got to schedule WESCO for my genny and haven't had the fuel line bracket done. Do you have an extended warranty?

 

[Sum Escape]

Sorry, They = local Cummins guy. I called them to schedule my aftercooler maint and Valve lash Adj. They stated they would be replacing all my injectors. ( both motors ) No doubt if I didnt call it would not have been done .

Rob

I have the QSCs (355 hours) as well and have had the fuel rail recall done...no other issues with them. What is up with the injectors that I should know Rob? Thanks in advance for your help.

 

[Robski97]

Guys ,
I know nothing about the injector recall. I can just tell u they said there was one and they replaced the injectors on both motors. There never very forthcoming. They dont leave any reciepts either. I do not have an extended warrty.

Rob

PS Brian. the quotes at work . ill email u monday.