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Running on one engine
If I shut down one of my engines to save fuel, am I supposed to block the shaft of the dead engine in order to protect the transmission? And what is the best way to do this?
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Running on one engine
On 5/19/2015 12:24 AM, wenders wrote:
If I shut down one of my engines to save fuel, am I supposed to block the shaft of the dead engine in order to protect the transmission? And what is the best way to do this? I don't think it's necessary or even desireable. -- Respectfully submitted by Justan Laugh of the day from Krause "I'm not to blame anymore for the atmosphere in here. I've been "born again" as a nice guy." |
Running on one engine
On Tue, 19 May 2015 05:24:54 +0100, wenders
wrote: If I shut down one of my engines to save fuel, am I supposed to block the shaft of the dead engine in order to protect the transmission? And what is the best way to do this? === I've had numerous conversations with my mechanic and others on this subject. The problem arises because the transmission depends on circulation of oil for lubrication and cooling. The pump which creates that circulation is driven by the engine side. Some say that if you run slowly (under 7 kts or so), that there is little or no risk. I've done this on numerous occassions without experiencing any problems, and have observed no abnormal temperatures as measured by an IR heat gun. Others say that it's OK if you briefly restart the engine every hour or so to ensure lubrication. On the other hand both my mechanic and the transmission manufacturer (Twin Disc) strongly recommend against it, and consequently I have stopped doing it. The generally accepted method of securing the shaft from rotation is to chain it down, i.e., wrap the coupler with chain and fasten it to a strong point on the boat. Obviously this has to be done with the boat stopped. There is a secondary issue that you may not be aware of. The shaft log and/or cutlass bearing frequently rely on a flow of cooling water from the engine raw water system to prevent wear and over heating. If the associated engine is shut down, that flow will no longer be present unless you have installed cross over hoses from the opposite engine. Bottom line for me is that the risks out weigh the potential fuel savings. Rebuilding or replacing a transmission costs many thousands of dollars plus the inconvenience and down time. Chaining down the shaft is tricky and has its own risks. A possible alternative is to leave the engine running at idle speed instead of shutting it down. Diesel engines do not like to idle for long periods of time however and will eventually develop carbon deposits and/or stuck rings. |
Running on one engine
Maybe I'm not thinking right, but how can running only 1engine save fuel? To achieve any speed to get to plane arnt you having to over tax that one engine, causing higher fuel consumption?
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Running on one engine
On 5/20/2015 8:19 AM, Tim wrote:
Maybe I'm not thinking right, but how can running only 1engine save fuel? To achieve any speed to get to plane arnt you having to over tax that one engine, causing higher fuel consumption? Slow trolling at idle speed is the reason that makes most sense to me. I doubt fuel savings would amount to much. -- Respectfully submitted by Justan Laugh of the day from Krause "I'm not to blame anymore for the atmosphere in here. I've been "born again" as a nice guy." |
Running on one engine
On Wednesday, 20 May 2015 09:19:06 UTC-3, Tim wrote:
Maybe I'm not thinking right, but how can running only 1engine save fuel? To achieve any speed to get to plane arnt you having to over tax that one engine, causing higher fuel consumption? Reminds me of those vehicles that shut down half the cylinders when cruising. I wouldn't touch one of those vehicles...it's quite hilly here in the city and the province in general. |
Running on one engine
On Wed, 20 May 2015 05:19:05 -0700 (PDT), Tim
wrote: Maybe I'm not thinking right, but how can running only 1 engine save fuel? To achieve any speed to get to plane and you having to over tax that one engine, causing higher fuel consumption? === You don't run on one engine if you want to get on plane. The fuel savings comes from running slowly at less than hull speed which minimizes drag. The problem with running that slowly is that both engines end up at or slightly above idle speed. That's particularly bad for diesels since they are prone to developing carbon deposits and sticky rings when they idle for a long time. The fuel savings, which is minimal based on my experience, comes from operating the remaining engine at a more efficient RPM range. Internal combustion engines require a certain amount of power at idle speed just to overcome friction, run pumps and alternators, spin cam shafts, etc. That's all wasted power that does not show up at the flywheel or contribute to forward motion. It's not all gravy however since the prop for the engine which is shut down is now creating drag, as do the rudders which have to compensate for the off center thrust. I have done controlled tests with our boat, running slowly at around 7 kts on a single engine, and letting the idle prop spin freely. The fuel save was 20% at best. |
Running on one engine
True North wrote:
On Wednesday, 20 May 2015 09:19:06 UTC-3, Tim wrote: Maybe I'm not thinking right, but how can running only 1engine save fuel? To achieve any speed to get to plane arnt you having to over tax that one engine, causing higher fuel consumption? Reminds me of those vehicles that shut down half the cylinders when cruising. I wouldn't touch one of those vehicles...it's quite hilly here in the city and the province in general. Lots of hills where i live. Friend got his wife a new GMC SUV. He says 28 on the highway and around town 14 mpg with the big V8 shuts down 4 cylinders when cruising. Friend with a new Corvette says, ease up to 90 mph and cruise on the 4 cylinder mode. 46 mpg. Sounds like they are doing something correct. |
Running on one engine
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Running on one engine
On Wed, 20 May 2015 13:43:02 -0500, Boating All Out
wrote: In article , says... I have done controlled tests with our boat, running slowly at around 7 kts on a single engine, and letting the idle prop spin freely. The fuel save was 20% at best. That's a significant savings. Since you didn't lock down the idling shaft, what are the downsides? === The most significant downside is possible damage to the transmission. On a boat with no crossover cooling water to the shaft log, it and the cutlass bearing are also at risk. On my boat we have active fin (Naiad) stabilizers which minimize rolling in heavy seas. They are much less effective at slower speeds so that is a secondary draw back. |
Running on one engine
Bill, I have a friend with a new Chevy truck with the shut down system. Yes, at 75 cruise on, he said he's getting about 28 mpg.
I remember in the early 80's the Caddilacs had that 8-6-4 system that when it worked it did well. But it didn't work very well for long. A lot of them caught on fire... |
Running on one engine
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Running on one engine
True North wrote:
On Wednesday, 20 May 2015 09:19:06 UTC-3, Tim wrote: Maybe I'm not thinking right, but how can running only 1engine save fuel? To achieve any speed to get to plane arnt you having to over tax that one engine, causing higher fuel consumption? Reminds me of those vehicles that shut down half the cylinders when cruising. I wouldn't touch one of those vehicles...it's quite hilly here in the city and the province in general. People much smarter than you have accounted for your concerns when they developed those systems. |
Running on one engine
On Wednesday, May 20, 2015 at 8:05:11 PM UTC-4, Username wrote:
People much smarter than you have accounted for your concerns when they developed those systems. ****face krause has been " running on one engine" for years right here. |
Running on one engine
On Wed, 20 May 2015 20:03:00 -0400, Username
wrote: wrote: On Tue, 19 May 2015 05:24:54 +0100, wenders wrote: If I shut down one of my engines to save fuel, am I supposed to block the shaft of the dead engine in order to protect the transmission? And what is the best way to do this? Dunno much about inboards but the outboard guys say you really should swap props if you are running on one engine to prevent "lugging". If it was properly propped to run 2 in the power band, one is going to be straining at much more than hull speed. Most twins have counter-rotating props. Swapping them would make you run in reverse. === I think you misunderstood his comment. He did not mean swapping them port to starboard and vice versa. He meant swapping them for new props with a lower pitch, sort of like shifting to a lower gear. |
Running on one engine
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Running on one engine
Tim wrote:
Bill, I have a friend with a new Chevy truck with the shut down system. Yes, at 75 cruise on, he said he's getting about 28 mpg. I remember in the early 80's the Caddilacs had that 8-6-4 system that when it worked it did well. But it didn't work very well for long. A lot of them caught on fire... Lots more computer power in cars these days. |
Running on one engine
I can understand running one engine for a 'trolling' speed. But the OP was vague on what boat, engines, and purpose he's trying to achieve besides merely 'saving fuel'
He hasn't been back either. Lol! |
Running on one engine
On 5/21/15 9:22 AM, Tim wrote:
I can understand running one engine for a 'trolling' speed. But the OP was vague on what boat, engines, and purpose he's trying to achieve besides merely 'saving fuel' He hasn't been back either. Lol! A friend has a 25 foot outboard fishing boat with a full transom bracket. It has a 300 hp Yamaha centered on the platform, and there's a 20 hp outboard mounted on the bracket to the side of the big Yamaha. Steering bracket connects both to the steering wheels. Nothing unusual around here. He runs in and out of the harbor on the small outboard, and also uses it to troll for stripers. The small outboard has no problems maintaining the 6 mph harbor speed limit. |
Running on one engine
On 5/21/2015 9:22 AM, Tim wrote:
I can understand running one engine for a 'trolling' speed. But the OP was vague on what boat, engines, and purpose he's trying to achieve besides merely 'saving fuel' He hasn't been back either. Lol! Mebee we've been trolled ;-) -- Respectfully submitted by Justan Laugh of the day from Krause "I'm not to blame anymore for the atmosphere in here. I've been "born again" as a nice guy." |
Running on one engine
On 5/21/2015 9:30 AM, Keyser Söze wrote:
On 5/21/15 9:22 AM, Tim wrote: I can understand running one engine for a 'trolling' speed. But the OP was vague on what boat, engines, and purpose he's trying to achieve besides merely 'saving fuel' He hasn't been back either. Lol! A friend has a 25 foot outboard fishing boat with a full transom bracket. It has a 300 hp Yamaha centered on the platform, and there's a 20 hp outboard mounted on the bracket to the side of the big Yamaha. Steering bracket connects both to the steering wheels. Nothing unusual around here. He runs in and out of the harbor on the small outboard, and also uses it to troll for stripers. The small outboard has no problems maintaining the 6 mph harbor speed limit. Nice to know, but not relevant to this discussion. :-) -- Respectfully submitted by Justan Laugh of the day from Krause "I'm not to blame anymore for the atmosphere in here. I've been "born again" as a nice guy." |
Running on one engine
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Your point is well taken. I would never try to put the boat on a plane with only one engine. I was more thinking of trolling at low rpm on one engine.
I would still want to block the dead shaft, but still have not quite figured out how. Appreciate your input. |
Running on one engine
Bill, I take it you're talking about a band brake?
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Running on one engine
Tim wrote:
Bill, I take it you're talking about a band brake? Yup. But you could implement a small mechanical disk brake also. |
Running on one engine
Wayne.B wrote:
On Wed, 20 May 2015 20:03:00 -0400, Username wrote: wrote: On Tue, 19 May 2015 05:24:54 +0100, wenders wrote: If I shut down one of my engines to save fuel, am I supposed to block the shaft of the dead engine in order to protect the transmission? And what is the best way to do this? Dunno much about inboards but the outboard guys say you really should swap props if you are running on one engine to prevent "lugging". If it was properly propped to run 2 in the power band, one is going to be straining at much more than hull speed. Most twins have counter-rotating props. Swapping them would make you run in reverse. === I think you misunderstood his comment. He did not mean swapping them port to starboard and vice versa. He meant swapping them for new props with a lower pitch, sort of like shifting to a lower gear. You are probably right. I'm not afraid to admit when I'm wrong! |
Running on one engine
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Running on one engine
On Sun, 24 May 2015 08:54:52 -0400, wrote:
On Sat, 23 May 2015 09:42:08 -0400, Wayne.B wrote: On Sat, 23 May 2015 06:55:21 -0400, wrote: If you think you need the kicker for a backup, that may be another issue but it is just going to get old and rot on that bracket. It is cheaper to sell it and buy a tow pirate contract === I agree if you do all of your boating within cell phone or VHF range. But if you go 40 or 50 miles offshore, twin engines of some sort have a lot to recommend them. This is where the discussion of the prop deal came about, on the real boat board. Trying to idle home from 50 miles out or half way to the Bahamas is not that attractive. That is where carrying a set of spare props with "single prop pitch" came in but it would need to be slick calm to be able to swap props at sea. On an inboard you are diving. If I was going to do this I might look into that system with the standard hub and replaceable blades for my spare. === None of the alternatives are real good if you lose an engine in the Gulf Stream. You don't really need to run at idle speed however, it will just seem that way if you're used to running on plane at 25 kts or so. You can actually cover quite a bit of ground at 7 or 8 kts if you have the patience to tough it out. Don't ask me how I know. :-) |
Running on one engine
Wayne.B wrote:
On Sun, 24 May 2015 08:54:52 -0400, wrote: On Sat, 23 May 2015 09:42:08 -0400, Wayne.B wrote: On Sat, 23 May 2015 06:55:21 -0400, wrote: If you think you need the kicker for a backup, that may be another issue but it is just going to get old and rot on that bracket. It is cheaper to sell it and buy a tow pirate contract === I agree if you do all of your boating within cell phone or VHF range. But if you go 40 or 50 miles offshore, twin engines of some sort have a lot to recommend them. This is where the discussion of the prop deal came about, on the real boat board. Trying to idle home from 50 miles out or half way to the Bahamas is not that attractive. That is where carrying a set of spare props with "single prop pitch" came in but it would need to be slick calm to be able to swap props at sea. On an inboard you are diving. If I was going to do this I might look into that system with the standard hub and replaceable blades for my spare. === None of the alternatives are real good if you lose an engine in the Gulf Stream. You don't really need to run at idle speed however, it will just seem that way if you're used to running on plane at 25 kts or so. You can actually cover quite a bit of ground at 7 or 8 kts if you have the patience to tough it out. Don't ask me how I know. :-) When I go on long range tuna trips out of San Diego, most of the trip cruising is at 9-11 knots. And on a 7-8 day we end up as far south as Rocas alijos. 460 miles from Point Loma harbor. |
Running on one engine
On 5/24/2015 5:51 PM, Wayne.B wrote:
On Sun, 24 May 2015 08:54:52 -0400, wrote: On Sat, 23 May 2015 09:42:08 -0400, Wayne.B wrote: On Sat, 23 May 2015 06:55:21 -0400, wrote: If you think you need the kicker for a backup, that may be another issue but it is just going to get old and rot on that bracket. It is cheaper to sell it and buy a tow pirate contract === I agree if you do all of your boating within cell phone or VHF range. But if you go 40 or 50 miles offshore, twin engines of some sort have a lot to recommend them. This is where the discussion of the prop deal came about, on the real boat board. Trying to idle home from 50 miles out or half way to the Bahamas is not that attractive. That is where carrying a set of spare props with "single prop pitch" came in but it would need to be slick calm to be able to swap props at sea. On an inboard you are diving. If I was going to do this I might look into that system with the standard hub and replaceable blades for my spare. === None of the alternatives are real good if you lose an engine in the Gulf Stream. You don't really need to run at idle speed however, it will just seem that way if you're used to running on plane at 25 kts or so. You can actually cover quite a bit of ground at 7 or 8 kts if you have the patience to tough it out. Don't ask me how I know. :-) That would be a great day of cruising on the Grand Banks we had. :-) I have to admit though, after operating boats that could cruise at three times the speed of the GB, I found it's 6-7 knot cruise to be very relaxing. You just plan your trips for what it can do. The other nice thing is it could go from Boston to Fernandina Beach, FL on one tank of fuel. |
Running on one engine
On Sun, 24 May 2015 20:06:54 -0400, "Mr. Luddite"
wrote: On 5/24/2015 5:51 PM, Wayne.B wrote: On Sun, 24 May 2015 08:54:52 -0400, wrote: On Sat, 23 May 2015 09:42:08 -0400, Wayne.B wrote: On Sat, 23 May 2015 06:55:21 -0400, wrote: If you think you need the kicker for a backup, that may be another issue but it is just going to get old and rot on that bracket. It is cheaper to sell it and buy a tow pirate contract === I agree if you do all of your boating within cell phone or VHF range. But if you go 40 or 50 miles offshore, twin engines of some sort have a lot to recommend them. This is where the discussion of the prop deal came about, on the real boat board. Trying to idle home from 50 miles out or half way to the Bahamas is not that attractive. That is where carrying a set of spare props with "single prop pitch" came in but it would need to be slick calm to be able to swap props at sea. On an inboard you are diving. If I was going to do this I might look into that system with the standard hub and replaceable blades for my spare. === None of the alternatives are real good if you lose an engine in the Gulf Stream. You don't really need to run at idle speed however, it will just seem that way if you're used to running on plane at 25 kts or so. You can actually cover quite a bit of ground at 7 or 8 kts if you have the patience to tough it out. Don't ask me how I know. :-) That would be a great day of cruising on the Grand Banks we had. :-) I have to admit though, after operating boats that could cruise at three times the speed of the GB, I found it's 6-7 knot cruise to be very relaxing. You just plan your trips for what it can do. The other nice thing is it could go from Boston to Fernandina Beach, FL on one tank of fuel. === Yes, we're in the process of completing an 800 nautical mile loop through the Bahamas, average speed about 8 1/2 knots, all done on one tank of fuel. And it is relaxing on a nice day. Once you're in open water just set the autopilot and the radar alarm, sit back, and let the boat take you for a ride. To quote a relevant line from the book "Perfect Storm," "No one ever gets tired of looking at the water." |
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