Not all HP is created equal!

BillD

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Something to ponder. Comparing engine HP.

Two great Cummins engines !!!

QSC 500 hp vs QSM 450 hp
8.3 liters 10.9 Liters

Weight?, QSM has about 1,000 lbs. more of IRON than a QSC.
Duty?, QSC, light vs QSM, medium to continuous duty

HP output, QSC at 1800 rpm maybe 200 hp vs QSM at 1800 rpm maybe 300-350 hp.
Torque?, QSC at 1000 rpm close to nothing vs.... QSM serious torque at idle to 1,000 for driving BIG hydraulics.

Maintainance?, QSM, about as simple and cheap as it gets in high annual hour usage. QSC, as in all high hp pleasure duty marine diesels, constant vigilance of SWAC circuit.



Which identical boat would win a buoy race on seatrial day??

The QSC, if that matters. LOL

For what it's worth,

Bill D
 

Pedlyr

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It all comes down to fuel. How much fuel gives you what HP you are looking for. Which, of course, is a function of RPM's.

With the CAT ECM's you hook up ET (Electronic Technician, a fancy name for laptop/software). You can get a total amount of fuel burn for the engine in gals. Many times this is used in determining overhaul periods, not engine hours.

Betcha the QSC uses more fuel even though it is a smaller displacement.
 

MouseTrap

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It was either Enzo Ferrari or Carol Shelby that stated: "Horsepower sells cars, torque wins races."

I would imagine it would be the same for boats too.
 

Overkill

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Depends on how long it is, continuous duty should win on the long haul if it doesn't run out of fuel first.
 

Estimator

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Question

What the word on John Deere engines? I have been asked if I would consider putting this brand in a new build. Some "special " pricing out there right now

Any thoughts?

Resale ??
 

badabing

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hmmm, well i just took out a good ole dd71 series and i gotta tell you....a chevy 350 has more torque but i did replace it with a qsm11 rated at 405hp at 2100 rpm and this motor has oodles of torque and is running a 50 qpm hydraulic vane pump running up to 3000psi and the qsm loves it
 

Helen L

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Chevy 350 more torque??????? Are you comparing your $100k engine to a $15k engine? A f/i to n/a? Don't be silly.
 

badabing

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i was just pointing out that the 71 series is a very poor example of a torquey motor.....i have had a 6-71 in my boat for 10 years through 3 overhauls and finally just replaced it with a qsm11 405, don't get me wrong, they (71 series) have their good aspects but torque definitely is not one of them
 

Helen L

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520 NM (350) vs 526 NM (4-71 @ 2100 rpm) 560 NM @ 1400

OK, what 350 is that? How is it tuned?

Just sayin
i was just pointing out that the 71 series is a very poor example of a torquey motor.....i have had a 6-71 in my boat for 10 years through 3 overhauls and finally just replaced it with a qsm11 405, don't get me wrong, they (71 series) have their good aspects but torque definitely is not one of them
I wasn't comparing a 6-71 to the QSM11. It's stupid to compare an engine that's 70+ years old with a new one. But compared to others in it's old school class, it had good torque. Most of my friends' draggers have 8-71s and swear by them. 6-71 baseline torque numbers compared to 3208 numbers and you'll guess why more 71s were in draggers.
 

BillD

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I enjoy starting these discussions!!

I wasn't comparing a 6-71 to the QSM11. It's stupid to compare an engine that's 70+ years old with a new one. But compared to others in it's old school class, it had good torque. Most of my friends' draggers have 8-71s and swear by them. 6-71 baseline torque numbers compared to 3208 numbers and you'll guess why more 71s were in draggers.
Always good insight and information with ANY topic!!

I always pickup a bit of knowledge!
 

Helen L

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Generally the commercial boats are looking for super reliabilty over pumped up horsepower torque. You could make a lot more from a 71, but decrease the lifespan greatly. I'm not in this to go fast and drop big cash every few years on rebuilds. That's not to say I don't appreciate a fast DE and high output diesel. For my application I want something that will run 15,000 hours before a rebuild though. If I was having a DE of my dreams built new, I'd still put an 8-71 in it.
 

badabing

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well i guess we can agree to disagree....first a new qsm 11 405 hp was only about 44k not near the 100k but hey whats 56 grand, and like i said 71 series are great engines....i put over 15000 hours on mine in the last 10 years but i don't see how to compare a 2 stroke diesels torque to any 4 stroke diesel torque no matter the year made, but i may be missing something here
the cummins 10.8 liter has been around since the early 70s and marinized here and there before cummins marinized it and sold it as a marine engine
not trying to argue just stating my firsthand experience
 

BillD

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Cummins Rule !!!!

well i guess we can agree to disagree....first a new qsm 11 405 hp was only about 44k not near the 100k but hey whats 56 grand, and like i said 71 series are great engines....i put over 15000 hours on mine in the last 10 years but i don't see how to compare a 2 stroke diesels torque to any 4 stroke diesel torque no matter the year made, but i may be missing something here
the cummins 10.8 liter has been around since the early 70s and marinized here and there before cummins marinized it and sold it as a marine engine
not trying to argue just stating my firsthand experience
QSM 405,

Great engine, detuned 11 liter beast.
 
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