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Old 12-22-2011, 05:00 AM   #21
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RE: What's your cruising speed.

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.

*
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Old 12-22-2011, 06:03 AM   #22
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RE: What's your cruising speed.

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.*
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Old 12-22-2011, 06:09 AM   #23
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RE: What's your cruising speed.

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.
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Old 12-22-2011, 06:27 AM   #24
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RE: What's your cruising speed.

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.
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Old 12-22-2011, 06:38 AM   #25
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What's your cruising speed.

Quote:
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.
*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
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Old 12-22-2011, 06:38 AM   #26
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What's your cruising speed.

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
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Old 12-22-2011, 07:21 AM   #27
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What's your cruising speed.

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
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Old 12-22-2011, 08:52 AM   #28
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RE: What's your cruising speed.

Quote:
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.
*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.
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Old 12-23-2011, 03:40 AM   #29
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RE: What's your cruising speed.

"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 .
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Old 12-23-2011, 05:04 AM   #30
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RE: What's your cruising speed.

Quote:
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 .
*Also dripless packings...they need a water feed crossover for single engine ops (at least a*PSS does)
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Old 12-23-2011, 05:38 AM   #31
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RE: What's your cruising speed.

15kts@5-6gph...not too shabby!
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Old 12-23-2011, 05:49 AM   #32
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RE: What's your cruising speed.

Quote:
FlyWright wrote:
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.
*Flywright, something doesn't seem to jive here. *I had that same engine in a Prairie 29 with about a 25ft waterline and the engine was happiest about 18-1900 RPMs(6.5kts). *It is a 2600RPM engine. *I think running it at 2300RPMs is a bit much. *Not only that, if I ran mine at *that RPM in that little Prairie it would be doing damn near the same speed as your boat(at least 7.5 and with a lot less waterline). *Are you sure your tachs are correct??? *Are you sure your props are properly pitched? *And what RPM can you attain at WOT?

Personally, I would not feel comfortable using 2300RPM as a "normal" power setting. *Not knowing the power curve of that engine but I would assume it to be well over 80% and quite possibly over 90%. *Old tech diesels aren't very happy in that realm nor will they give you the service life they are known for.
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Old 12-23-2011, 08:06 AM   #33
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RE: What's your cruising speed.

Quote:
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*Flywright, something doesn't seem to jive here. *I had that same engine in a Prairie 29 with about a 25ft waterline and the engine was happiest about 18-1900 RPMs(6.5kts). *It is a 2600RPM engine. . .

_________

Off topic, but had an airline pilot here at the house yesterday checking out our P29 before going out to Texas to give your boat a serious look. *(ours isn't for sale, he wanted to check ours out with the wife for room, etc.)
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Old 12-23-2011, 10:19 AM   #34
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RE: What's your cruising speed.

John, FlyWright,

If the engine is in excellent shape, if it's warmed up and cooled down at the proper rate, if it's oil and all other maint is fresh and most importantly if the engines are propped right running 300 rpm down from rated rpm should'nt present any problems whatsoever. If Fly is 100 rpm over propped the above is not true at all. With my 3000 rpm rated engine I cruise at 2300 most of the time (700 down) and run frequently at 2500 (500 down) and would'nt hesitate to run 2700 or even 2800 for several hours but to do that all the time even w my "run'em hard attitude" would not be an option. I think you're right John. 2300 (300 down) on an old OR new engine is just a tad too much load for continious operation. If it were my boat I'd run 2000 - 2100rpm and make sure I was under propped a tad or spot on at 2600 at WOT. The above is 100% opinion.

Eric
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Old 12-23-2011, 10:31 AM   #35
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RE: What's your cruising speed.

I cruise at 400-500 off the top. *-450 gives me 27 knots on flat, slack water.

It's really tough being in the minority again.
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Old 12-23-2011, 10:47 AM   #36
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RE: What's your cruising speed.

Isn't fuel-rate consumption a better indicator of an engine's load?* A 2500-RPM engine is operating at less than 50% power at 1250 RPM.**A 4.5-GPH engine at 2500 RPM operating at 2200 RPM and*consuming 3.5 GPH is at 80% power.* I thought such a power setting*was healthy for the engine but not for one's pocketbook.
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Old 12-23-2011, 11:46 AM   #37
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What's your cruising speed.

Quote:
ksanders wrote:
*Very cool.

I havn't tried single engine running.
*Kevin, as FF mentioned you need to check with the tranny manufacturer to see if free wheeling the tranny does no damage. My ZF marine tranny's according to the manual are OK to free wheel indefinitely but a quick check with ZF Marine and I was advised to free wheel no more than 30 minutes before swapping engines. So I set a timer on my chartplotter for 20 minutes and swap engines.*

A quick check to see if it really is advantageous to operate single engine is to note the speed at whatever rpm you want to consider, say 1300 rpm. Shut one down and note the speed after re-trimming and allowing the boat to slow. If the speed single engine is more than half the speed with two engines operating then it is more economical. Depending on the loss of speed it may not be worth it. At 1300 rpm I drop from 7.8 kts to 6.8 kts single engine. Well worth it for me, probably due to my smaller boat and the engines being relatively close together.*

As the saying goes; individual results may vary.*


-- Edited by timjet on Friday 23rd of December 2011 12:50:38 PM
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Old 12-23-2011, 12:13 PM   #38
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RE: What's your cruising speed.

Quote:
ksanders wrote:

I havn't tried single engine running.
*Kevin--- Whether or not you can run on one with the other prop and transmission freewheeling will depend on two things.* One, your transmission must be capable of being freewheeled with the engine shut off.* Some are, some aren't.* The BW Velvet Drive, for example, can be freewheeled safely according to the manual at slow speeds, which they define as sailing or trolling speeds.

The other factor is whether or not your shaft logs have cooling water feeds from the engines' raw water cooling system.* On our boat, for example, the shaft logs are cooled/lubed by a water feed picked off from the engine's raw water cooling system and fed to a fitting in the log.* This is because at speed the forward cutless bearing in the log does not recieve sufficient--- or any--- cooling/lube water from outside the boat.* So this water is fed to the bearing by the engine's raw water system.* If the engine is shut down no water will be fed to the log and if the shaft is freewheeling the log, bearing(s), and shaft will get extremely hot in a very short time even at slow speeds, and permanent damage to the bearings, shaft, or both will occur.

So even though our Velvet Drive transmissions can be freewheeled at slow speeds, our shafts cannot if the water feed is not present.* So if we have to shut an engine down the shaft has to be tied off (there is provision for this in the engine room).* And the non-turning prop will generate so much turbulence and drag there would be no value in doing this to try to save fuel.* We'd probably use less fuel with both engines running than cruising with one shut down.

So make sure you understand your transmissions' operating parameters and shaft log cooling/lube requirements before you attempt to run on one.
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Old 12-23-2011, 01:23 PM   #39
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RE: What's your cruising speed.

Quote:
FlyWright wrote:
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.
*Al

What is your RPM at WOT and do you know the curb weight for a 34'*?*

I usually run about 2400 at 8.5 knots (seems to be the sweet spot for the 6.354's) and WOT is 2800.

(ps.*So after spending a week floating around*at 7 knots, how long does it take your mind to catch up to charging down the runway at 110 knots?? * )

Larry B
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Old 12-23-2011, 04:52 PM   #40
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RE: What's your cruising speed.

You could cross-cool your stuffing boxes by connecting the two cooling lines with T-junctions, a short cross hose and a few clamps. That way either engine cools both P & S bearings.

Besides having cutlass bearing*cooling lines coming off my transmission coolers, each of my shaft tubes has another fitting with a hose leading from small reservoirs to gravity-feed*water or ATF-type fluids for cooling the logs. That according to my engine surveyor (this extra system was empty and not in use when I bought the boat and the surveyor felt it was a bit redundant -- sort of a "try it if you like but it's not necessary" thing).**
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