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Discussion Starter · #1 ·
I found a wonderful old post by WarpP:

"I had a 8V71 take off after it warmed up, because someone put three of the oil rings in upside down. By the time we got the plywood against the turbo intake, 10 seconds, it was screaming at 3000 rpm and climbing. The emergency air shut on the supercharger was too far on to the engine to grab, thank god for that piece of plywood. Very impressive, a ton of iron trying to destroy itself and there is no way of escape."

Good to know.

I have a question about 8V71TI diesels (8 cylinders, 71cc per cylinder, turbo charged).

What is the optimal cruising speed and maximum range of the following Deep V planing hull?

1. Fuel tank 4000 liters (879.8769932 UK Gallons)
2. LWL 48.031496063 feet
3. Beam 4.3 Mts
4. Draft 1.52 Mts
5. Gross Tonnage 31.63
6. Total Engine Power 656.48 kW. (880 Hp)

Assuming the useable capacity of the tank is 87% of the maximum, that would provide 765.49 UK gallons (3480 liters).

For optimal cruising speed do you take the square root of LWL
(6.93047589008143) and multiply it by 1.34 as you would for a full displacement hull? 9.28 knots.

As it is a Deep V planing hull, do you multiply the square root of LWL by 2 giving 8.31 knots?

It seems from Stapletons Power Boat Bible that V471 normally aspirated engines with 55mm injectors needed 11,355 liters to cover 3,818 nm in 460.8 hours of running time.

Adding 8 UK gallons per hour for each 5mm increase in the size of the injectors does not answer the question because they are four cylinder engines.

If anyone can figure out what the optimal cruising speed (for maximum range) would be, and what the maximum range is, that would be great
 

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Discussion Starter · #4 ·
You are quite correct. It is cubic inches.

This is all new to me.

Have not yet bought the boat. Trying to figure out whether it has any sort of decent range, and whether I could run it on one engine, using the other as a backup.

Thanks for responding.
 

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Discussion Starter · #6 ·
Detroit V871TI

That makes perfect sense. Thank you.

I think it is going to be a trial and error job by watching consumption at various speeds unless I can find out from the manufacturer.
 

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Discussion Starter · #7 ·
Detroit Diesel

Cool.

I most definitely shall not mess about with the engines :)

You are right about parts availabilty. There are engine overhaul kits on e-bay.

Frankly I love the sound of these engines. They make your hair stand on end :)

Now all I need is a piece of plywood :)

Sincere thanks,
 

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Discussion Starter · #11 ·
Detroit 8V71

Many thanks to you both for your observations. Really helpful and interesting.

It would be nice to have the best of both worlds, which is to say it would be nice to have a 100hp diesel with its own prop as well.

Then there could be economical long distance passage making, and serious range, combined with the ability to turn on the powerful diesels and zip around bad weather :)
 
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