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Old 12-21-2011, 05:58 PM   #1
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What's your cruising speed.

Just curious what speed you cruise at. As an aside, how slow would you be willing to go if it halved your fuel consumption?
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Old 12-21-2011, 06:03 PM   #2
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What's your cruising speed.

We run the engines (FL120s) at about 1700 rpm which gives us a cruise speed through the water of about 8 knots. Used to be a tad over 8 knots but we had the props pitched down*a few years ago so now it's usually a wee bit under 8 knots.

FL120s are happiest in the 1600-1800 range and running them any slower than 1500 rpm runs the risk of not getting them up to temperature.

We don't like cruising at 8 knots--- we'd rather be doing 18 or preferably 25--- so we are not willing to slow down any more no matter how much fuel it saves. Fuel is the cheapest thing in boating anyway--- if we were concerned about fuel burn and cost we wouldn't be boating at all.


-- Edited by Marin on Wednesday 21st of December 2011 07:04:47 PM
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Old 12-21-2011, 06:05 PM   #3
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What's your cruising speed.

I know I could reduce fuel consumption if I cruised slower than 8.5 to 9.0 kts. However, I cruise at 1650 to 1700 rpm regardless of SOG. Better for the engines. Depending on an ebb or flood current, I'll realize 7.0 to 11.00 kts around the San Francisco bay area.

-- Edited by Giggitoni on Wednesday 21st of December 2011 07:07:40 PM
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Old 12-21-2011, 06:43 PM   #4
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RE: What's your cruising speed.

Twin Yanmar 500hp seem to be happier at 25-27 knots.
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Old 12-21-2011, 06:44 PM   #5
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RE: What's your cruising speed.

We run at about 1750 rpm which pushes us at 8.5-9 kts. The engines just don't sound right under 1650 rpm and over 1900 I feel my wallet leaking.
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Old 12-21-2011, 06:46 PM   #6
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RE: What's your cruising speed.

I can push it out to 8.5 kts....but I prefer to hold it down to 7kts for fuel efficiency....
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Old 12-21-2011, 06:53 PM   #7
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What's your cruising speed.

Can't quite make 8 knots at full throttle.* Usuallly go about 7 knots.* Normally go faster (through the water) against the tidal current*and slower with the current.* Find that's the best fuel- and time-wise.* Seems like I'm either fighting or flowing with a 2-knot-or-more current.


-- Edited by markpierce on Wednesday 21st of December 2011 08:16:02 PM
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Old 12-21-2011, 06:57 PM   #8
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RE: What's your cruising speed.

7 knots for me and we like that speed.
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Old 12-21-2011, 07:03 PM   #9
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RE: What's your cruising speed.

I know, I'm not a trawler but... 3,150 produces 24-25kts. That's where the engine sounds and feels the best. Anything more and the secondaries open and so does the wallet!
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Old 12-21-2011, 07:18 PM   #10
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RE: What's your cruising speed.

Exactly 7.5 knots at somewhere around 1800 RPM, I think. I can get up to 10+ wide open but at that point I'm just digging a trench.* My tachs are all jacked up so I really never know what my RPM is so I just go by the sound and vibration.* Gonna get that fixed in the Spring.
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Old 12-21-2011, 08:04 PM   #11
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RE: What's your cruising speed.

I'm still working with my own early numbers, but the PO has one of those plastic stick labels next to the tach that says "best cruise 2600", and that comes out to a restful 7.5 knots turning a 22 X 13 prop "or so it is marked". This boat was re-powered with a 140 Yanmar over the original 90 Volvo, but they kept the same prop. Since the Volvos seem to be most comfortable at 6.5 knots, I have not been able to figure out why this boat has turned into a more comfortable 7.5 knot cruiser. Fuel consumption seems to be about the same too. It's possible that when the Yanmar was installed, they re-pitched the old prop too, but I haven't had any reason to pull the boat and check. Regardless, three sources record a silky smooth 7.5 knots at 2600 and 2.2 GPH. It drops to 1.65 GPH at 6.5 but doesn't feel a smooth. 3600 WOT gets 9.5 knots with a pronounced squat.
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Old 12-21-2011, 08:18 PM   #12
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RE: What's your cruising speed.

Quote:
Budds Outlet wrote:
I know, I'm not a trawler but... 3,150 produces 24-25kts. That's where the engine sounds and feels the best. Anything more and the secondaries open and so does the wallet!
*I'm deficient:*get "nose bleeds" traveling on a boat*going faster than hull speed (when I'm paying for the fuel.)
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Old 12-21-2011, 08:28 PM   #13
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What's your cruising speed.

Quote:
markpierce wrote:
*I'm deficient:*get "nose bleeds" traveling on a boat*going faster than hull speed (when I'm paying for the fuel.)
*Mark, you just have a little touch of "dollar separation anxiety". *A little spending therapy will help you get over it. *As a matter of fact if you will send me your credit card info, I'll help you.


-- Edited by Moonstruck on Wednesday 21st of December 2011 09:28:50 PM
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Old 12-21-2011, 08:36 PM   #14
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RE: What's your cruising speed.

In our 4788 Bayliner with 330 cummins...

We get 1.7 NMPG at 7.8 knots

If we slow down to 6.8 knots we get 2.7 nmpg

If we speed up to 15 knots we drop to .68 nmpg

We think thats pretty good for this size boat.
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Old 12-21-2011, 08:57 PM   #15
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RE: What's your cruising speed.

Quote:
ksanders wrote:
In our 4788 Bayliner with 330 cummins...

We get 1.7 NMPG at 7.8 knots

If we slow down to 6.8 knots we get 2.7 nmpg

If we speed up to 15 knots we drop to .68 nmpg

We think thats pretty good for this size boat.
*Kevin, your low speed numbers are very good.

My 35 Carver with the same 330 Cummins at 7.4 kts gets 1.6 nmpg.

At 6.8 kts I get 2.2 nmpg.

But my higher speed numbers are a bit better:

At 19 kts I get a shade under 1 nmpg.*

However check this out. On one engine at 7.2 kts I get a whopping 2.5 nmpg. So when I go slow which is about half the time, I'm single engine.*
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Old 12-21-2011, 09:05 PM   #16
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RE: What's your cruising speed.

Quote:
healhustler wrote:
I'm still working with my own early numbers, but the PO has one of those plastic stick labels next to the tach that says "best cruise 2600", and that comes out to a restful 7.5 knots turning a 22 X 13 prop "or so it is marked". This boat was re-powered with a 140 Yanmar over the original 90 Volvo, but they kept the same prop. Since the Volvos seem to be most comfortable at 6.5 knots, I have not been able to figure out why this boat has turned into a more comfortable 7.5 knot cruiser. Fuel consumption seems to be about the same too. It's possible that when the Yanmar was installed, they re-pitched the old prop too, but I haven't had any reason to pull the boat and check. Regardless, three sources record a silky smooth 7.5 knots at 2600 and 2.2 GPH. It drops to 1.65 GPH at 6.5 but doesn't feel a smooth. 3600 WOT gets 9.5 knots with a pronounced squat.
*Same transmission ratio?
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Old 12-21-2011, 10:07 PM   #17
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RE: What's your cruising speed.

Quote:
Moonstruck wrote:
*Mark, you just have a little touch of "dollar separation anxiety". *A little spending therapy will help you get over it.
*Gotta save up for those inevitable yard bills.
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Old 12-21-2011, 11:49 PM   #18
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RE: What's your cruising speed.

We seem to travel best ~ 7 knots, which is about average SOG by GPS at 1850 rpm which is where Lotus seems to feel happiest. (L120)
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Old 12-22-2011, 02:33 AM   #19
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RE: What's your cruising speed.

8 Kts at 2300 RPM seems to be where my Perkins 4.236's are happy. I get 2.1 NMPG at that speed. 7 Kts/2100 RPM gives me closer to 2.5 NMPG and is much quieter, but feels too slow. Call me a speed freak.
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Old 12-22-2011, 03:44 AM   #20
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RE: What's your cruising speed.

Our LWL ia close to 48, 49 ft , so we travel at SL x 1.0 for a cheap cruise at 7K.

This is 1200 -1300 RPM and under 3 gph.

Sure 12k is possible but at 10-12 gph its not often .
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