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?

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?

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
 

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?

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.