Carver 406 Handling & GPH

I have a 406, have done the loop, done the east coast from Florida to Martha;s V, and the Bahamas more times than I can count. Currently in Chattanooga, TN. For the money the Carver 406 is a great buy, especially now with the market down.

I generally run at about 2500 RPM when in open waters. Otherwise I run
just above and idle. At 2500 I get about .7 MPG, at 900-1000 RPM I get
about 2.3MPG. I did add an additional AC unit to keep it cool to my like, thus
I have three units.

(mine in a 370HP Cummins).....

I do most of the wrk myself, and will be happy to share findings/fixes with you.

Good luck

abt 6-8 to get that mpg, at that speed I usually am on one engine at about 900-1100 rpm....I spend alot of time in fla waters, boat was in Ft Laud for the last
18 months

I've considered single engine operation too as the fuel savings are significant. However after talking to a tyranny repair tech in Ft Lauderdale who said not to let the tyranny free wheel for more than 30 min I've changed my mind.

You got good advice. Keep a 2x4 cut to length handy to block the shaft from moving when one engine is down.

How much improvement are you talking about on one engine? While I've seen some say running on one engine reduces fuel consumption, I've also read by others that less strain by running two engines just over idle uses about the same fuel. I have no idea, just asking for all views.

I once took a 36 Carver out of Glen Cove heading for S.I. with 1/4 tank on each side (just enough to make it). Under the Throgsneck we blew the port tranny. With no way to transfer fuel we ran on the one tank and I can't remember every seeing a fuel gauge drop so fast. Ran out at the #2 just north of the Verizano. When running on one engine you're fighting the boats desire to turn the whole way, and that burns fuel. It may work out at idle, but you're always tempted to push harder than will do any good speedwise, and that is not efficient. I DK the numbers, but given 2 I'll always run on 2, at least on a boat that size.

I had an oil cooler blow on my port engine a few years ago. I had a full tank (290+ gallons). Had to motor back 20 miles (just over idle) on the starboard engine only. Refilled the tank after fixing the cooler and found I burned over 40 gallons! That was only .5 MPG at 1000 RPM at ~6 MPH.

Running 2 engines at 1000 RPM gives me 8 MPH and I get 1.5 MPG.

I thought so, and there are the numbers. Thanks. Many times with a displacement hull it pays to go on one, but seldom with a planing hull.

That sounds like a good conclusion; displacement hull can achieve fuel savings going on one engine, but not a planing hull. Hull speed seems to be the optimum fuel savings, about 8 knots or so, or 1.34 x the square root of the waterline length; if you have the time.

well, its me again, don't know how much cruising some people do, I do have
over 28000 miles, over the past 10 years, much on one engine, why bother with spinning two props in no wake zones, and from Miami to Jacksonville 75% is no wake, the Erie and Trent Severn are also no wake, not to even mention the number of small towns with marina's that you need to slow down for.....the ZF rep, and the and the ZF manual says that running at idle, in gear or out of gear has no ill effect....but to each his own

I believe I've done a bit more than 28,000 miles in the last 10 years, but there's still a lot I don't know. So I'm open to considering different ideas. I just did a bunch of checking, and I can find nothing definitive saying there's a fuel savings or not. Other than when an engine goes down I don't run on one engine, so I'm no authority. In the one time I ran to empty on the only tank I could get to because of a blown tranny, I know I used a lot more fuel in that one engine than I would have normally (about double), but then I used none on the other side. So if there is any fuel savings it is negligible at best. What is definitive is that you lose maneuverability, and you have to work harder at the helm. Then there's the fact that most recreational boats don't run long or hard enough (150-200 hrs. a year avg.) to keep their motors properly lubricated. Giving your motors a break isn't doing them a favor. Finally, although I'm no engineer, I've read more than one owner's manual which advised to not let a prop freewheel. You're advised to block it if you must go to one engine because your shaft is turning with no lubrication.

The significant fuel savings on one engine I was referring to above was taken from data I obtained on my Carver 355 ACMY with twin Cummins 6B TA 5.9 M3's and ZF Marine HSW 800 2:1 tranny's.

Twin operation at 1300 rpm gave a GPS speed of 8.3 kts and a total fuel burn of 4.9 gal/hr (from Cummins fuel burn charts) or 1.69 NM/gal.

Single operation at 1300 rpm gave a GPS speed of 7.1 kts and a total fuel burn of 2.45 gal/hr (half the above) or 2.9 NM/gal. That's 58% less fuel burn.

My props are relatively close together and at 7.1 knots in calm seas (intercoastal) once I set the rudder correction for the asymmetrical thrust I could not tell I was on one engine.

My conclusion: The loss of thrust from the shut down engine and the resulting asymmetrical thrust is paid for in the reduced speed from 8.3 to 7.1 kts. I don't know if the running engine fuel flow increased to maintain 1300 rpm due to the added drag, but some have said this is so, in which case the Cummins fuel curves don't apply.
Also at idle speeds, a large portion of the engines power is used just to keep the engine running; circulation pump, raw water pump, alternator, etc and moving that massive crankshaft and fly wheel, power that is not going to the props. As rpm is increased the percentage of power produced to keep the engine running is considerably less and far more is going to the prop.
A more in depth discussion on single engine operation can be found here:
http://www.trawlerforum.com/forum.spark?aBID=115492&topicID=38913265&p=3
Draw your own conclusions.

My tranny manual also states that no harm will occur to a free wheeling tranny. I called ZF Marine in Miramar FL and asked a tech this same question. His reply, it's OK to run a free wheeling tranny for about 30 minutes, but that's about it, it does need lubrication that requires the engine to be running. He suggested that if I wanted to run single engine, swap the engines every 30 minutes. My take: These tranny's are too expensive to fool with, block the tranny if you're going to run single engine.

Then there is always that little wrinkle of what to do if you have to make a sudden dodge to the side you're running on like when you meet a current from a side channel or spot a tree stump. 2.5 gph savings at $5 per gal. is $12.50. In the unlikely event that you actually cruise that way for 8 hours a day that's $100 (about what you'll give in tips on a day of boating). Then you have to account for the extra miles you might cover by veering off your course line (heavy boats, those with props close together or with a full keel will do better than light planing hulls, but now we're into trawlers), the extra time it takes to get to your destination, the start-up fuel burn whenever you get into close quarters so you can maneuver and the wear of running that motor cold and unlubricated. Now add in the potential repair costs. All-in-all, unless you're running at a steady speed 24/7 on say an open ocean voyage I see any savings (if there is any) derived from running on one hardly worth the risks or inconvenience, especially when you consider that you'll probably only run your boat for 150 hours total during the year.
Saving money is wonderful. Turn off the extra lights at home and turn down the thermostat, get rid of that SUV. Boating is done for fun. If it causes you to count pennies on you day off, maybe it's the wrong recreational activity. Boating is not an activity you get into to save money.

Now we are telling others what the true value and enjoyment of yachting is? Did you miss the part where he said that he DECIDED to do this on his own accord? What makes you think that the things you enjoy about the yachting lifestyle you choose would be the keys to everyone's enjoyment? We are happy for you and your ability to choose whether fuel savings is something that is worthwhile for you and the enjoyment of your yacht. Does everyone need to operate per your SOP?

yep, all you said is true, in my case I run between 400 and 500 hours per year. this year will an exception...open ocean, with swells and current is not practical for one engine, nor is a place like hells gate in NY,

Simply putting out what I've learned to help inform and to learn myself. I don't, nor even care to tell anyone how to run their lives or budget. Chill. For the record, I don't pay for one ounce of fuel, nor boat for enjoyment (although it is an addiction). My job is to protect my clients and their assets, and to save them money wherever I can do so purdently. However, anybody I've ever met in boating that sweated every dime spent was either miserable, not long in boating or both. Boating is a pastime in which trying to save a dollar very often involves losing $100.

TIMEJET, good post

Concerning the transmission (sorry...the term 'tranny' gets me weirded out ) freewheeling...I had a thought that I couldn't seem to wrap my head around.

If, let's say the port engine, were shut off and then put into a forward gear, would the prop freewheel? Sorry if it seems like a dumb question, but the more I think about it, the more I come up with 2-3 answers.