What's your cruising speed.

Baker · Dec 23, 2011

Baker · Dec 23, 2011

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.

flagold · Dec 23, 2011

Baker wrote:
*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.)

Nomad Willy · Dec 23, 2011

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

Moonstruck · Dec 23, 2011

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.

markpierce · Dec 23, 2011

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.

timjet · Dec 23, 2011

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

Marin · Dec 23, 2011

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.

Edelweiss · Dec 23, 2011

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

Formosa · Dec 23, 2011

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).**

Marin · Dec 23, 2011

saturnaisland wrote:
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.

*

You could and this has been suggested numerous times on this and other forums including the GB owners forum.* But for whatever reason, nobody ever seems to do it.* I don't know of any twin-engine owner with shaft log cooling who has done this even though they know it can be done.* My guess is that the instances of having to shut an engine down are few and far between, and the fuel savings of running a boat like* GB on one engine with one shut down have been shown to be fairly insignificant.* The founder of the GB forum ran accurate tests of this with his own boat and his findings in table form show that there's not much--- or in some cases anything--- to be gained by running a GB-type boat on one.

It may make a more significant difference with different hull types or cruise speed envelopes, however.

Formosa · Dec 23, 2011

I agree, Marin, that fuel savings alone aren't*necessarily enough to justify this (I'm familiar with the Dreamer's test stats and 2Bucks' FloScan readings on this forum) and I know*this has been hashed to death on TF but I still think single engine running can make sense.

We enjoy putting along at 6.5-7.0 knots -- I'm aware that your preference is a little more speed but we are ex-sailors -- which means 1400-1500rpm with twin Lehmans. That speed is probably*not loading the engines as much as it should so you could run one engine closer to the 1700-1800*sweetspot and get the same speed. Beyond loading the engine better, you may save 50-100 engine hours per year meaning less wear & tear and maybe less maintenance (fluid/filter changes, injector service, etc).*

I've connected the P & S cooling lines but still run both engines most of the time. It is still early days with this particular boat so time will tell on this subject.

And to the original question, I guess it is 7.0 knot cruising at about 1500 rpm with the twins.

*

Marin · Dec 23, 2011

saturnaisland wrote:*...we are ex-sailors -- which means 1400-1500rpm with twin Lehmans. That speed is probably*not loading the engines as much as it should ...

*

That rpm range is a little low for Fl120s.* Why not run at 1600, which won't increase your fuel usage enough to care about, get there a wee bit sooner and make your engines quite a bit happier?

chc · Dec 23, 2011

Our Californian 34 is powered by Detroit 8.2L's @ about 250 hp each. Boat displaces 18,000# officially; practically speaking, I would figure that to be closer to 20 - 21,000#. On our ICW cruise we averaged 8.4 kts, burned (avg) 5.3 gph. However, in all fairness, those are misleading figures. The ICW is slow going, with lots of idle zones for wake issues, bridge delays, etc. For normal, around the Chesapeake Bay, type of cruising, I plan on a total fuel burn of 10 gph, 8 - 9 kts cruise. WOT we get about 20 -22 kts; I don't even bother to figure fuel burn at that setting. RPM settings : about 63 - 65%. depending on the chart you select, loaded WOT on these engines is 3000 rpm; I generally run @ 1900 -2000. !

Edelweiss · Dec 23, 2011

chc wrote:
Our Californian 34 is powered by Detroit 8.2L's @ about 250 hp each. Boat displaces 18,000# officially; practically speaking, I would figure that to be closer to 20 - 21,000#.*

____________________________________________

So if I remember correctly those were about 500 CI and turbo'd.* Is this a later model boat or was this a repower?

I wouldn't be surprised on the weight, my 37' Cali. aft cabin is 15 ton's hanging in the straps with 500 gals. fuel on board.

Larry B

*

Baker · Dec 24, 2011

nomadwilly wrote:
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

*I run my boat(Yanmar 4LHA-STP) at 300 under max continuous and 500 under max rated. *But it is all about power curve. *To give you an idea of the power curve of my engine: it produces 190hp@3100RPM(Max continuous) and 240hp@3300RPM....so as you can see, a LOT of power shows up on the top end meaning the curve is very steep towards the upper end of the RPM range. *I cruise at 2800RPM at approx 140ish hp. *These Yanmars are built to scream and I have no problem running them in this manner. *But like I said, I have owned a 4236 and while I would have no problem running it at 2300RPM, I wouldn't do it on a regular basis. *I would imagine there power profile to very similar to a Lehman and I don't think any Lehman owner would feel to warm and fuzzy about using 2300 as a normal every day power setting.

chc · Dec 24, 2011

Larry;
Yep, 500 CI w/turbos. Not sure if it was repowered along the way. It is a 1984 boat. I think I am the 3rd owner, so these are very likely the original engines.

Edelweiss · Dec 24, 2011

chc wrote:
Larry;
Yep, 500 CI w/turbos. Not sure if it was repowered along the way. It is a 1984 boat. I think I am the 3rd owner, so these are very likely the original engines.

A lot happened after Marshal sold the Californian name.* I just hadn't seen a GM in a calif.*before, Perkins and Cats were the standard.* That is a lot of pony power, I'll bet it can fly.* I'm the first owner on mine and still running on the original, twin na Perkins, engine build.*

Doc · Dec 24, 2011

My 1989 Californian 45' MY with 485 hp 6-71 TIB's got exactly one mile to the gallon at 1200 rpms. 8.75 kts. At 2200 rpms (out of a max of 2500) I got .4 mpg at 20 kts. The 13.5 kw Kohler gen set was always running.

The tug at 1800 rpms got 2 mpg and was going 8.75 kts. It had a single 330 Cummins. The 12 kw Northern Lights gen set was very rarely running.

Norwester · Dec 24, 2011

Here are some numbers for our 46 Westcoast with a single Cummins 270B.* At 1400 rpm we're at 8 knots burning 2.5 gallons/hr.* At 1600 rpm we're at 9.2 knots burning 3.6 gallons/hr.* At 1800 rpm we're at 10 knots burning 4.8 gallons/hr.* Top end is 2600 rpm.* I generally run at 1400-1600 rpm.* My wife likes to run at 2,000+.* I tell her that past 1800 rpm the boat is pushing more water, burning more fuel and she isn't even gaining 1 knot.* I still catch her inching it up all the time.*

The boat wasn't designed as a trawler, but because of the single it is very efficient for it's size.*

Lyle

bshanafelt · Dec 24, 2011

7.0 knots , 1.4 gal/hr 1400 rpm; 8 knots, 1.8 gal/hr 1650 rpm
single cummins 210hp.
boat is 20,000lbs

Baker · Dec 25, 2011

Norwester wrote:
Here are some numbers for our 46 Westcoast with a single Cummins 270B.* At 1400 rpm we're at 8 knots burning 2.5 gallons/hr.* At 1600 rpm we're at 9.2 knots burning 3.6 gallons/hr.* At 1800 rpm we're at 10 knots burning 4.8 gallons/hr.* Top end is 2600 rpm.* I generally run at 1400-1600 rpm.* My wife likes to run at 2,000+.* I tell her that past 1800 rpm the boat is pushing more water, burning more fuel and she isn't even gaining 1 knot.* I still catch her inching it up all the time.*

The boat wasn't designed as a trawler, but because of the single it is very efficient for it's size.*

Lyle

*Those are some nice numbers. *It is quite rare you find a boat like that with a single....I would even say extremely rare!!! *And they usually go for cheap because most people looking for that type of boat want twins(and/or speed). *Anyway, I dig your rig!!!

Norwester · Dec 25, 2011

John,

You're right, it is a rare boat.* Out of 24 made, I only know of 3 with a single.* The advantages are that it is very fuel efficient for the size, and also very quiet and smooth when running 8-9 knots.* It has a wide open engine room and is simple and easy to service.*

We bought it as a bank repo in Vancouver, B.C. in 2009.* It was a lot less expensive than many other boats of her size and construction.* I attribute that to being a repo and also to the fact that fewer people would be looking for a single in this style of boat.*

I started out looking for a sedan style with twins, but by the time we found this boat I wanted a very fuel efficient aft cabin style with a cockpit and a Cummins diesel.* This boat fits our needs well.

Lyle

Bendit · Jan 31, 2012

I know this is an old thread, but I thought there was*a thread where members had posted pictures of their vessels underway. Anyway*I finally have a*pic underway taken by a friend from land on Auckland' anniversary day (last Monday).

We are cruising at our normal speed of 9.2 kn at 1250 rpm. We are burning 18 litres or 4.7*gallons per hour. I notice that the bow which is steeply raked but quite rounded with plenty of bouyancy, not a fine entry, pushes quite a lot of water forward and the stern has lifted from its normal attitude. *9.2 kn is exactly max. displacement speed. (1.34 x sq root wl).

The hull is long and narrow at the waterline so fairly efficient for a semi-planing configuration.

At 8 kn or 1100rpm we burn 11 litres or 2.8*gallons per hour, and at a fast cruise of 12 kn, 45 litres or 11.7 gallons per hour

Peter B · Feb 1, 2012

Looks nice Jeff. I reckon your best compromise cruise speed would be about 9kn @ 1200rpm, and you'd be saving a bit. In the pic she looks like she is just moving out of her cruise economy comfort zone. Great pic tho - wish I could get one of our boat from a similar vantage point, but they don't exist where we boat. Unless we knew someone with a place on Russell or McLeay Island overlooking one of the channels we frequent, but sadly we don't.

ktischler · Feb 1, 2012

Running our twin Lehman 120's at 1600 rpm gives us about 7.2 kts and a fuel burn rate of about 3.6 gph. If we push them up to 1750 or so we can get 8 kts, but fuel burn goes up to around 5 gph. Burning almost 30% more fuel to gain .8 kts is just not worth it, in our opinion. So we putt-putt along happily at 1600.

-- Edited by ktischler on Wednesday 1st of February 2012 08:14:41 AM

Bendit · Feb 2, 2012

Peter B wrote:
Looks nice Jeff. I reckon your best compromise cruise speed would be about 9kn @ 1200rpm, and you'd be saving a bit. In the pic she looks like she is just moving out of her cruise economy comfort zone. Great pic tho - wish I could get one of our boat from a similar vantage point, but they don't exist where we boat. Unless we knew someone with a place on Russell or McLeay Island overlooking one of the channels we frequent, but sadly we don't.

*Thanks Peter,

I agree that a little slower would likely be a bit more efficient, but backing off reduces turbo boost to almost zero and the engine feels happier with a pound or two of boost. I am happy to potter about fishing etc at 1100 rpm but for passages, 1250 feels best.

Compared with the Riviera 36 we had before this, we are doing 1/2 the speed and using less than 1/4 the fuel.

Baker · Feb 2, 2012

I would say that Bendit, you have quite an efficient boat. I personally would cruise her at 8kts....which I would imagine to be around 1.1 or so which is where you really wanna be for efficiency.

markpierce · Feb 3, 2012

Mid-day yesterday in Carquinez Strait, I made 4.9 knots SOG at 2200 RPM going east but 8.7 knots at 1300 RPM going west.* Let's say water currents influence my cruising and engine*speeds.

Now realize I said the same thing on Dec. 21 but with less specificity.

-- Edited by markpierce on Friday 3rd of February 2012 01:54:15 PM

nwboater · Feb 3, 2012

We used to cruise at 1700 rpm for 8 knots. Then we spent a summer cruising with friends in a smaller, slower boat. We reduced our*speed to 6.8-7.5 knots and found that the engine loafted along (quietly!) at around 1400 rpm (1.5 gal/hr max. possibly less). We now cruise at 1500 rpm and take whatever speed she gives us. Nice.

What's your cruising speed.

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