fuel consumption 8V71 naturals

[ron6785]

To be totally honest, I REALLY like our 53 on plane which is contrary to the way I felt for 4 1/2 years on the boat. But last cruising session in Sep/Oct I ran her for about an hour on plane for the trip between where we were anchored and the marina and I felt like she did EVERYTHING better.

That short trip convinced me that I wanted to operate on plane a LOT more. I've been thinking that planing may become our normal operating mode from now on but we'll see...

We don't have the opportunity to boat as much as we used to so the price of fuel for doing this vs displacement cruising is not an issue, regardless of what the prices do.

Mike, are you running 8/71 naturals, and getting up on plane? How many knts do you need to stay up? At what RPMS?

[MikeP]

No, not naturals, TIs. Sorry if I didn't make that clear earlier. With the TIs in our 53MY it takes WOT to sloooooowly get onto plane (flaps full down!) and around 2000RPM to hold her there at around 15.5-16 K depending on conditions. She will not reliably stay on plane below that RPM. WOT with a clean bottom and freshly cleaned shafts/props will usually produce 17.5-17.8K. When we bought her and she didn't have all the stuff in her that we have now, she did 18.5.

[Brian Degulis]

MikeP's figures look very reasonable...in a 45 to 55 foot twin screw heavy planing hull, like Hatts, it's REALLY hard to get 1 NMPG over 8 or 9 knots. That's why real long range boats, like Nordhaven typically have a single engine and cruise around 6 knots, maybe 7 knots or so...for the reasons stated in earlier posts: speed takes a lot of power and that means a lot more fuel consumption.

I've tried slow cruising and besides the fact my engines don't seem to like such slow running as much as 10 or 11 knots, I get really bored: 10 knots gets you where you are going in about 6/10 or 60% of the time at 6 knots...on a half hour run, nobody cares much but if you are running say 100 miles, 16.67 hrs (at 6 knots) vs 10 hs (at 10 knots) is really tedious!!! (Besides I need to walk my dog.)

That's the way I feel 10Ks is the magic # any slower starts to drive me nuts especially on a long run. I'm cheap and the fuel savings is considerable but I just can't get used to less than 10.

Brian