On Long Voyages Do You Run On One?

Paulkarlsven

Paulkarlsven

New Member
Dec 29, 2010
436
Port Stephens, Australia
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Engines
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Hi All,

I am about to do a 300nm voyage in a twin 454 V drive sports cruiser and I am trying to conserve as much fuel as possible to reduce the expense. This is a boat relocation trip and not a holiday as such.

So for those that have done this sort of trip have you ever shut one engine down and just slow motored on the other?

I will be doing this from the Gold Coast in Queensland, Australia down to Port Stephens in NSW, Australia. I also hope to be able to use the EAC to make a few knots for free.

I would always have the option of reverting back to both engines if I needed to run for safe harbour due to inclement weather.
 
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I’ve looking into this. We have too many long no wake zones and we keep getting more.

First, one combination will leave you without power steering. That does not sound like that big of a deal until you do it for a few hours. It’s not a muscle group that you can develop with push-ups or other normal exercise. The front of my chest got soar. Not the pec mussels, the dead center of the chest.

Second, when I had to replace a engine coupler I was given this practice as a possible reason for the early failure. Then I was handed a 4 figure repair bill.

Third, after real world unscientific number crunching that I did, the fuel saves was negligible if anything.
 
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Use both engines. Wild guess, whatever efficiency you gain by only running one engine (internal and drive friction losses for example) you'll lose by asymmetrical thrust, having to compensate with the rudder, which adds drag, and the drag of the freewheeling prop.

Best regards,
Frak
 
On our 340 (454s at 310 hp) we get .75 MPG at 3600 RPM with a speed of 28 MPH. At 1200 rpm we burn 4.5 gph at 7.5 mph. 1.6 MPG. This is with full fuel and water.
 
On one 829 mile trip we burned 1128 gallons engines ran 49.5 hours .735 miles per gallon, 22.8 gallons per hour, averaged 16.8 mph. This includes running the generator. Trip was a 7 day cruise.
 
Thanks for the responses there are a lot of good reasons to stay on both engines which I had not given much thought to, one of which is the power steering.

I guess if I keep the RPM down to the 1200 to 1500 range I will probably get the best bang for buck.

In my advantage is that the engines will have brand new risers, plugs and filters plus be fully serviced. The hull and running gear are currently having new anti-foul applied so she will be pretty clean underneath to do the trip.

I will be using the autopilot a lot of the time, I have never had this option before so it will be interesting to see how it performs.
 
Good luck & have a SAFE trip. :smt001

Don't forget to take the camera. :thumbsup:. We like pics. :smt001
 
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1988 340 DA, 454's, Using floscan and GPS my best MPG is 3200 RPM with both engines.

Faster and mileage plummets. Slower and I fall off the plane so mpg goes down. Real slow with 1 or 2 engines never gets the mpg of 3200.

The only time 1 engine works out is below 5 knots.
 
sfergson727 said:
Throw power steering out of the mix, you don't have it. Throw the couplers out too, you have V-drives, not stern drives. The risks you have are your shaft seals. If you do not have a crossover cooling to them (assuming they are dripless) the unpowered one will burn itself up.

Run both engines at 1300 RPM, as said above, you should get around 1.5 mpg. I recently ran a trip up to Mackinac Island and back, 665 miles at that RPM for 90% of the trip. We saved at least 40% on our fuel burn, had I otherwise gone at normal cruise.

It goes without saying, even though the autopilot is steering, make sure you have someone on lookout duty at all times. Additionally, get real familiar with setting up alarm rings around the boat with the radar, as it will get your attention if you miss something. Note on the first picture, we've traveled 81 miles, then note the elapsed time. It took us 35 hours to go 330 miles, and that was with me cheating on the speed occasionally. If you are more disciplined than I, you can expect about 48 hours to complete the trip.

BTW I had a crew of 3 adults on board for shifts. Make sure that your crew sleeps when it is their time off, otherwise you'll all be exhausted, the whole trip. Have fun!
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Wow thanks for the info that was really useful to me. I say power steering because, I think I should have made it known, that my boat has a Seastar hydraulic drive system installed on it.

I definitely intend to keep watch, I am hoping at this stage to have two crew with me Having said that I intend to put in before nightfall each day, no sense in killing ourselves for the sake of a couple of days plus I like to have a good dinner and a bit of a relax in the evening. We will head off at sparrow fart each day.:grin:

At least it is outside the Humpback migration season so the likelihood of running into migratory pods will not be of too much concern.:smt001
 
I think there's more to the story here. I collected some data running single engine vs two engine and I concluded there may be some savings, and quite possibly considerable savings.
My Carver 355 ACMY with twin Cummins diesels gets 1.69 mpg at 8.3 kts and 1300 rpm. Single engine I get 7.1 kts and 2.45 mpg at the same 1300 rpm. Speeds were taken off the GPS and fuel flow off the Cummins fuel flow curves and converted to mpg.

The loss in speed from 8.3 kts to 7.1 kts accounts for the increase drag due to the rudder correction and the drag on the free wheeling prop and loss of thrust from the shut down engine.

What is not accounted for and this is important, is the increase in fuel flow on the remaining engine to maintain 1300 rpm. An engine will increase fuel flow slightly to maintain a set rpm when a slight load is imposed. How much this increased fuel flow would only be known with fuel flow indicators. The Cummins fuel flow curves of course do not account for this.

There was a lively discussion on the Trawler Forum several months ago on this issue: http://www.trawlerforum.com/index.spark?aBID=115492&p=3&topicID=38913265

Each boat will be different, for example my props are very close together creating very little asymmetrical thrust when one is shut down.

Another consideration is your transmissions. Some require the engine running to provide hydraulic pressure. The tranny will overheat without pressure. In my case the tranny manual says it's OK to allow the tranny to free wheel but when I called a repair facility the tech said that at most allow the tranny to freewheel for 30 minutes.

You can bet when fuel reaches $5 a gallon this issue will be further discussed.
 
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sfergson727 said:
Throw power steering out of the mix, you don't have it. Throw the couplers out too, you have V-drives, not stern drives. The risks you have are your shaft seals. If you do not have a crossover cooling to them (assuming they are dripless) the unpowered one will burn itself up.
Click to expand...

I ruined a Strong dripless seal on my port engine this past summer when I ran about 1 1/2 hours on one engine. I did not have cross over cooling, I do now, $3,000 later...

I would stay on two engines, run at 1200 RPM or less and you may save some money, but keep it on course without an autopilot will be a PITA...
 
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