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?

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

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

Twin Yanmar 500hp seem to be happier at 25-27 knots.

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.
Amazing Grace

I can push it out to 8.5 kts....but I prefer to hold it down to 7kts for fuel efficiency....

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

7 knots for me and we like that speed.
Steve W

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!

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.

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.

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!

Click to expand...

*I'm deficient:*get "nose bleeds" traveling on a boat*going faster than hull speed (when I'm paying for the fuel.)

markpierce wrote:
*I'm deficient:*get "nose bleeds" traveling on a boat*going faster than hull speed (when I'm paying for the fuel.)

Click to expand...

*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

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.

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.

Click to expand...

*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.*

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.

Click to expand...

*Same transmission ratio?

Moonstruck wrote:
*Mark, you just have a little touch of "dollar separation anxiety". *A little spending therapy will help you get over it.

Click to expand...

*Gotta save up for those inevitable yard bills.

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)

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.

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 .

6.5 knots. If I'm really in a hurry *I can go 7 knots.

I can almost hear the engine at that speed. I could give a crap less what my fuel consumption is.

*

We cruise at about 6.25 to 7*knots at 1600 to 1750 rpms and burn right around 1.8 gallons/hour.* The 6.25 knots is with the*paravains in the water.*

Well seeing how I haven't even been on a cruise yet in my New but Old 1976 Hatteras 48' Lrc that I purchased this past year I really don't personally know. *I spent a week on the boat down in Boca del toro, Panama trying to get motors running and getting rid of all the bad fuel I spent the evenings pouring over logs & info from previous owner and he noted on a graph that 1850 rpms was 8.2 knots was the sweet spot for fuel consumption/speed. *She has a waterline of 44' and she has a pair of 453 Detroit at about 112 or 120 hp, so not sure if that is good or not. *I assume if we slow down to 7 or 7.5 knots which if memory serves me right it was around 1550-1650 rpms fuel consumption seemed to drop significantly.

I met Chip another Lurker on this site just recently and he volunteered to go down with me along with a Delivery Capt he knew to help get boat prepped & ready for trip up to Guatemala here in the next few weeks so I bet after the first of the year I will have some hard numbers, its approximately 800-900 knt miles and possibly a 6 day trip. *This is why I love boating- for the adventure.

Maiden voyage 6 day trip? Wish us luck.

Since I'm in the Atlantic ICW, based out of Charleston, SC, I'm dealing with tidal currents most of the time. 2K RPM gives me about 7 knots at slack current, but over land, I'm making anywhere from 5 to 9 knots, depending on the tidal current. And this speed can change rather quickly when passing an inlet.

Most of the time, this speed is fine, but there are some long, boring areas where I'm tempted to step it up a little.

rwidman wrote:
Since I'm in the Atlantic ICW, based out of Charleston, SC, I'm dealing with tidal currents most of the time. 2K RPM gives me about 7 knots at slack current, but over land, I'm making anywhere from 5 to 9 knots, depending on the tidal current. And this speed can change rather quickly when passing an inlet.

Most of the time, this speed is fine, but there are some long, boring areas where I'm tempted to step it up a little.

Click to expand...

*In the ICW, going by an inlet coming in from the side is interesting. *You can have a 2 knot current pushing you when you get to it. *As you pass it you may have to deal with a 2 knot head current. *That is a 4 knot change in speed. *In a slow boat it can feel like hitting a wall.

Also currents coming in from the side of the ICW have a definite side setting affect. *One area I can think of about this is around McCellansville. *With narrow channels and 8' tides, attention must be paid.

One good thing about the currents is that they usually scour and keep the channels clear of silt. *However they also tend to pile it up at intersections.


-- Edited by Moonstruck on Thursday 22nd of December 2011 07:58:22 AM

We usually settle in on 6.5 knots with our highly overpowered 52 hp throttled back to warp factor 3 . . . though the vid shows higher.


-- Edited by flagold on Thursday 22nd of December 2011 07:40:01 AM

Otisguy-

check you EPIRB! but good luck!

I bought a boat in Ft Lauderdale and left the next morning for Charleston,SC without even being aboard for a sea trial (surveyor did one).

Big difference in where you will be and me in the ICW!!!!

Good luck again!


-- Edited by psneeld on Thursday 22nd of December 2011 08:22:16 AM

timjet wrote: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.

Click to expand...

*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.*

*Very cool.

I havn't tried single engine running.

"I havn't tried single engine running."

Check with the transmission mfg before you do, many can not be trailed , the prop must be stopped.

A prop brake frequently requires the shaft to be removed to be installed .

FF wrote:
"I havn't tried single engine running."

Check with the transmission mfg before you do, many can not be trailed , the prop must be stopped.

A prop brake frequently requires the shaft to be removed to be installed .

Click to expand...

*Also dripless packings...they need a water feed crossover for single engine ops (at least a*PSS does)