power specs for 1980 12V71TI

[captmikes]

Any one have info on HP, Torque, and fuel consumption for these engines.

 

[MicroKap]

ENGINES – 12V71TIs (N90 Injectors produce 690 BHP @2,300 RPM, 660 SHP; Twin Disk Transmissions (514 with 2:1 Ratio). Straight from Detroit Diesel.

Ross MacDonald, owner of a 60’ Hatteras Sportfish with 650 HP 12V71TIs reported the following:

1900 RPMs – 54 gallons per hour – 16 knots
1450 RPMs – 24 gallons per hour – 11 knots
1000 RPMs – 18 gallons per hour – 9.5 – 10 knots

1979 Hatteras 60C Performance Table from Motor Boat & Sailing

True RPM Knots MPH GPH
800 7.2 8.3 5.4
1,000 8.5 9.8 9.0
1,200 9.5 10.9 14.2
1,400 9.9 11.4 21.4
1,600 10.2 11.7 31.4
1,800 15.0 17.3 43.2
2,000 19.4 22.3 65.4
2,400 21.1 24.3 76.2

 

[rsmith]

Ross's # are what I saw on the 60 I fished on in the early 80's except we ran to the offshore canyons for day trips so we needed a little more speed for the 70 nm run. We ran 2150rpm which gave 60gph or so and 16.5-17.5 kts.Because these boats hold so much fuel and h2o speed and fuel burn vary with loading.(It was always faster coming home)
Now I'm going to make ppl mad. This hull design had the most pronounced pressure wave effect Ive ever seen. On the way offshore loaded we would be pushing 17kts as soon as we passed Five Fathom bank (off cape may) and entered deeper water (over 30') the speed would drop to 15kts and change.You could feel the loss of lift and the boat settle as it entered deeper water .Now this was in 1980 and we had just got the new loran c which replaced loran a. We were using the new Northstar that not only automaticly tracked both td's but gave a suedo ground speed, so it wasnt all that accurate.But I still position plotted on the chart and it was pretty close.
Did I mention the boat is stable as a rock?LMAO

 

[captmikes]

Thanks.
I should have given more detail. i have two of these in my 1973 53C. they were installed in 1980 by original owner who wanted more speed. they still run good but smoke some on startup and after idling for a while. am considering a pair of Cummins QSM-11's as replacements and wanted to compare power and torque curves. Talked to Tom Slane the other day and he indicated that his customer is happy with his. any suggestions?

 

[rsmith]

Was the name of the boat "Hey Bett" out of Cape May NJ?

 

[REBrueckner]

The 690HP DD engines are still only about 0.8HP/cube, so those engines are not really souped up and should give good service life. You can search here for other comments on the Cummins QSM-11's which have gotten good reports. The Cummins should be more fuel efficient.

It would be interesting to see the weight different between a pair of the two engines with their gears.

 

[jim rosenthal]

The M11s make about the same horsepower. They probably weigh less than half each of what a 12v-71 weighs, which means you would take a few tons of weight out of the boat. At a rough guess, I'd estimate the boat would be five to six thousand pounds lighter. That's a big difference even on a large boat like the 53C. They are also now available as remans for about 60K a pair, I think.

I think the Hookshot, the boat Tom installed these in, cruises about 19-20 kts. Uses a lot less fuel to do it as well. And you would have a lot more room around the engines, for service and all. You could probably fit a wine cellar in there with the space you free up. Sell your old engines on boatdiesel.com and you can stock the wine cellar.

 

[REBrueckner]

My early 1970's Hatteras brochure shows the 53C at 47,000 lbs. As usual, that seems light.

5,000 lbs is equivalent to about 625 gallons of fuel....aboard my 1972 48 YF that was almost a full load of fuel and I would guess my speed might have been a knot different....I can't imagine 3 knots speed change due to weight alone on a bigger boat, but whatever is accounting for it, about a three knot increase on less fuel in a BIG difference.....

Regarding smiths comments at the 5 fathom line, that is sure different than my 48 YF....I could tell from the trim of the boat when I was entering perhaps 15 to 20 foot depths....the stern would drop and I could tell from the sound of my waves we had enetere shallower water....the wake waves would break more...I was dragging more water and would always slow down from about 11 or 12 knots to 8 or 9 in shoal water....

I think we have had this discussion about shoal water performance previously!!!!

 

[rsmith]

My early 1970's Hatteras brochure shows the 53C at 47,000 lbs. As usual, that seems light.

5,000 lbs is equivalent to about 625 gallons of fuel....aboard my 1972 48 YF that was almost a full load of fuel and I would guess my speed might have been a knot different....I can't imagine 3 knots speed change due to weight alone on a bigger boat, but whatever is accounting for it, about a three knot increase on less fuel in a BIG difference.....

Regarding smiths comments at the 5 fathom line, that is sure different than my 48 YF....I could tell from the trim of the boat when I was entering perhaps 15 to 20 foot depths....the stern would drop and I could tell from the sound of my waves we had enetere shallower water....the wake waves would break more...I was dragging more water and would always slow down from about 11 or 12 knots to 8 or 9 in shoal water....

I think we have had this discussion about shoal water performance previously!!!!

My boat has come up between 58-64000 on the travellift gauge.I dont know how acurate that is but they use it to detirmine what slings to use so it must be close.
Pressure wave effect is the same as ground effect in a aircraft increaced lift when the bird is half a wingspan length from the ground. In a boat the h2o is not compressable like air so its more pronounced. If your off plane the wedge of water slows you down, on plane it gives more lift and you go faster.

 

[jim rosenthal]

Interesting....I don't know the relative weights of these two sets of engines, but I do clearly recall the performance numbers that Tom had seen on his 53 convertible, and they were impressive. And I think that boat had a tower and so on, so it wasn't a lightweight. The weight difference may be even more than I thought; I think M11s weigh about 2400lbs each, maybe a little more or less.

At a recent CYCA rendezvous, there was a 53 classic MY that the owner had repowered with Cummins 480CEs. It was strange to see them in the engine rooms previously occupied by the 8v-71TIs that had been in there; they look so small in that space. According to the owner, this boat will now cruise 17-19 knots and reach 21 or more at WOT. And those aren't even M11s...

 

[saltshaker]

I spoke with Tom on Friday. He is doing a 53C with QSM11's right now. He said it was a 3 ton weight savings and the water line rose 3". I don't know what the performance numbers are but I recall Hook shot could cruise 21kts and almost 24kts WOT with the 12V71TI's. That was with a new bottom and not much gear on board. I would expect the QSM11's to be a bit faster.

 

[saltshaker]

I was talking to Tom Slane today and asked him about QSM11's in the 53C. Hook Shot is the boat he is finishing right now. He expects a cruise in the 24kt range using 715HP QSM11's.