Discussion in 'Hatteras Yacht' started by Captain Dufy, Nov 8, 2015.
Same head, Same messed up back. When younger, I did it my self, Now near crip, I hire it out.
So the Army has different criteria, really just a set power for a limited amount of time, then rebuild and start all over. EPA emissions get waived. Their ground vehicle fleet is huge, old, and all over the globe with foreign military sales. Do you think the EPA is a factor in US military vehicles operating in the Middle East? I don't think so, just deliver the power required for the defense application for the duration specified and you are in business. Armed Force lives are on the line , and the EPA is a non-existent blip on their operational radar screen.
Even the Cummins VTA 903 is still alive and kicking at ungodly ratings from 900 - 1000hp in land vehicles. In marine form, the 903 only hit 450hp.
Ok now we have sound opinions about 8 71s and 12 71s. But can they efficently power a boat as heavy as an Hatteras without costing a fortune in fuel.I wonder if it would not be simpler to buy an older Hatteras ( cheaper) and repower with cats or cums?
And can somebody explain to me what the added TA or TI means and what do they add to the power and what is their consequences to reliability ? Then i can go shopping at least knowing what to look for. Thanks
Horse power moves a boat.
1/10 of a gallon per hour per horse power / 2 for a turbo diesel (each).
The modern fuel savings of the newer engines are the h p to weight, and the reduction of over fueled emissions when not making max horse power.
You want to move a Hatteras, this is where you start. Save weight, smarter fuel burn with no over fueling. These things cost bux.
Or spend the extra dollor$ and run what you have.
It may be a life time before the new equipment pays it's self off in the fuel savings (if ever). Then you still have an old boat.
I'm on the old front. My Detroit's ran well today from Jax to StAugustine. 100 gallons off shore against a south wind and current. Even tried some fishing off PV (No Joy).
A QSM11 would have consumed the same fuel with todays weather.
A calmer day on flat water, a QSM11 would of out run me on less fuel. It would take near 15 years of this for a (rebuilt) set of QSM11 to start saving money after the investment. The credit card interest alone would kill this on a south GA budget.
Even if one of my 12V71 blocks really cracks, it's still cheaper to stay with what I have. Heck, it's a 40 year old boat.
All Detroits have supper chargers, shortly called blowers and without any turbo charger, the term is naturaly asperated or NA.
TI - Turbo/Inter cooled. After the first air compression by the turbos, this hot air is cooled thru a raw water heat exchanger before it enters the blowers, then the air box, then the cylinder.
TA - Turbo/After cooled. The hot air from the turbos travels thru the blowers, then in the air box (V valley) is the heat exchanger that cools the air just before entering the cylinder. This offers the coolest/compressed air needed for extra horse power.
TA have a bit more plumbing and an interesting (may complicated) heat exchanger system.
It DEPENDS how you run them. At cruise they don't use terribly much more fuel than say a modern cat or man. Maybe 10% more fuel. Under the turbo's they're actually about 20% more efficient than new engines. I ran a Hatteras 75' MY with 12v71 TI's, at 1000 rpms we did 10.3 knots at 12 gph for both engines. A set of C 18's would probably be around 16-18 gph. At cruise a different story.......If you do the 1000 rpm crawl, you should run them up to cruise for 30 minutes every 6 hours to clean them out.......