DD 12v71 fuel flow and return rates

[Aussie Mike]

I'm installing fuel flow metres on my 12V71 turbos (650HP) and was wondering if anyone can help me with feed and return fuel rates per hour?
I need to determine what size of the flow meters. Gallon per hour or litres per hours for both feed and return. Thanks

 

[oscarvan]

The only help, limited as it is, I can offer is that I recall an 8V71 pumping 40-50GPH. Don't hold me to that.

 

[Briankinley2004]

 

[Aussie Mike]

That's exactly what I needed. Thanks so much.

 

[oscarvan]

I don't see the return flow in those graphs. Am I missing something?

 

[jmooney]

Gallon per hour used is not the same as fuel flow to the engine . A lot of fuel is returned . You need to know the amount of fuel initially flowing to the motor to size the fuel flow senders . I am looking into this and think that the flow senders should be sized as small as possible , as I think they would be more accurate at the lower range of flow . This is where most of us would be using the flow rates as a way of maximizing range and efficiency.

 

[racclarkson@gmail.com]

In my experience based on the time to pull and empty a tank into another on trips, I speculate as follows: At or about hull speed, fuel return is +/- 2X indicated flow; on plane, fuel return is +/- 3 to 3-1/2X indicated flow. Motors are 12V71Ti rated at 850 SHP; fuel flow is measured with Flow Scan and been found historically to be accurate viz totalizer vs. refueling.

 

[SeaEric]

That's exactly what I needed. Thanks so much.

Seems like longer ago than 2011. Time flies! I hope she's treating you well. Cheers!

 

[Aussie Mike]

When reading the graphs, I presumed "slip %" was referring to returning fuel. Am I mistaken?

Eric, I sold the boat in 2013 to a lovely couple (had to go bc of my divorce).
They lived on her and made many improvements over 7 years. They cruised all the east coast of AU and ended up in Cairns near the Great Barrier Reef. I kept in touch with them and I bought her back in much better shape than when I sold her 8 months ago.
She is berthed at Magnetic Is, again, close to the "reef".

 

[racclarkson@gmail.com]

When reading the graphs, I presumed "slip %" was referring to returning fuel. Am I mistaken?Eric, I sold the boat in 2013 to a lovely couple (had to go bc of my divorce). They lived on her and made many improvements over 7 years. They cruised all the east coast of AU and ended up in Cairns near the Great Barrier Reef. I kept in touch with them and I bought her back in much better shape than when I sold her 8 months ago.She is berthed at Magnetic Is, again, close to the "reef".

I believe he’s talking about prop slip, or efficiency. 28” pitch, for example, should move boat 28” forward every revolution. Being the prop operates in water, it’ll never achieve 100% efficiency.