Wayne.B wrote:

The other issue with single engine is wear and tear on the
freewheeling transmission.

Why let it freewheel, a freewheeling prop generates more drag than a
stationary one?

Cheers
Marty

On Tue, 20 Nov 2007 07:56:28 -0500, Martin Baxter
wrote:

Wayne.B wrote:

The other issue with single engine is wear and tear on the
freewheeling transmission.

Why let it freewheel, a freewheeling prop generates more drag than a
stationary one?

Cheers
Marty

That's true but it's not that easy to safely stop a 30 inch prop on a
2 1/2 inch shaft from free wheeling. This topic gets a fair amount of
discussion in the trawler groups. People have tried various jerry
rigged schemes like pipe wrenches and wrapped lines on the shaft tied
off to engine mounts but neither of those schemes holds much appeal
for me, and it is very advantageous to have the idle engine quickly
available for maneuvering. Everything's a trade off. There is no
disputing the fuel save however even though it may not be fully
optimal. We arrived in Florida at 5:00AM this morning after 2 1/2
days off shore. The fuel saved by running slow speed, single engine
was in the neighborhood of 150 gallons.

The other thing we've done that has saved significant amounts of fuel
is to install high output alternators on both engines, and couple them
to the house bank with battery combiners. The saving comes from
reduced generator run time since we can now use the inverter for
routine AC needs when underway without discharging the house bank. The
reduced generator time also lowers maintenance and replacement costs.

"Wayne.B" wrote in message
...

Why let it freewheel, a freewheeling prop generates more drag than a
stationary one?

Cheers
Marty

That's true but it's not that easy to safely stop a 30 inch prop on a
2 1/2 inch shaft from free wheeling. This topic gets a fair amount of
discussion in the trawler groups. People have tried various jerry
rigged schemes like pipe wrenches and wrapped lines on the shaft tied
off to engine mounts but neither of those schemes holds much appeal
for me, and it is very advantageous to have the idle engine quickly
available for maneuvering. Everything's a trade off. There is no
disputing the fuel save however even though it may not be fully
optimal. We arrived in Florida at 5:00AM this morning after 2 1/2
days off shore. The fuel saved by running slow speed, single engine
was in the neighborhood of 150 gallons.

The other thing we've done that has saved significant amounts of fuel
is to install high output alternators on both engines, and couple them
to the house bank with battery combiners. The saving comes from
reduced generator run time since we can now use the inverter for
routine AC needs when underway without discharging the house bank. The
reduced generator time also lowers maintenance and replacement costs.


Wayne, you have the wrong GB. :-)

(I run at 7.5 kts on a single, 120hp diesel, burning less than 2 gph)

Eisboch

On Tue, 20 Nov 2007 12:22:05 -0500, "Eisboch" wrote:

Wayne, you have the wrong GB. :-)

(I run at 7.5 kts on a single, 120hp diesel, burning less than 2 gph)

Maybe so but I can't see us out cruising for 5 and 6 months at a time
on a 36. That was our retirement model, 6 months in Florida and 6
months north on the boat. As it is, the 49 is completely loaded with
"stuff". My wife just can not understand the concept of traveling
light.

She *really* wanted a triple cabin boat, allegedly so there would be
room for grandchildren and their parents. This lead to some
interesting conversations with brokers when they'd ask how many
grandchildren we had. The answer was, and still is, zero. Both sons
got married this year however so that's a start. :-)

On Tue, 20 Nov 2007 15:41:58 -0500, Wayne.B
wrote:

On Tue, 20 Nov 2007 12:22:05 -0500, "Eisboch" wrote:

Wayne, you have the wrong GB. :-)

(I run at 7.5 kts on a single, 120hp diesel, burning less than 2 gph)

Maybe so but I can't see us out cruising for 5 and 6 months at a time
on a 36. That was our retirement model, 6 months in Florida and 6
months north on the boat. As it is, the 49 is completely loaded with
"stuff". My wife just can not understand the concept of traveling
light.

She *really* wanted a triple cabin boat, allegedly so there would be
room for grandchildren and their parents. This lead to some
interesting conversations with brokers when they'd ask how many
grandchildren we had. The answer was, and still is, zero. Both sons
got married this year however so that's a start. :-)

Neither do I.

Frankly, I'm glad because I don't want to...

Well, never mind. :)

"Short Wave Sportfishing" wrote in message
news

Believe it or not, there was a very thin film of ice forming on top of the
water in the back basin this morning.

Sign of things to come, I am afraid.

Eisboch

Wayne.B wrote:
On Tue, 20 Nov 2007 07:56:28 -0500, Martin Baxter
wrote:

Wayne.B wrote:
The other issue with single engine is wear and tear on the
freewheeling transmission.
Why let it freewheel, a freewheeling prop generates more drag than a
stationary one?

Cheers
Marty

That's true but it's not that easy to safely stop a 30 inch prop on a
2 1/2 inch shaft from free wheeling. This topic gets a fair amount of
discussion in the trawler groups. People have tried various jerry
rigged schemes like pipe wrenches and wrapped lines on the shaft tied
off to engine mounts but neither of those schemes holds much appeal
for me, and it is very advantageous to have the idle engine quickly
available for maneuvering.

Forgive my ignorance, I'm just not familiar with something this big. I
would think that you could just leave the tranny in gear and stop the
motor, or is there sufficient torque generated to turn the motor over?

Cheers
Marty
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On Tue, 20 Nov 2007 12:22:40 -0500, Martin Baxter
wrote:

Forgive my ignorance, I'm just not familiar with something this big. I
would think that you could just leave the tranny in gear and stop the
motor, or is there sufficient torque generated to turn the motor over?

The tranny is hydraulically actuated internally with its own pump
driven by the engine. With the engine off there is no pressure to
keep the clutches engaged. As long as the transmission is in gear
however, it is impossible to shut the engine down because of the prop
rotation being passed through. It's quite possible that there would
be enough torque to restart the engine if it did not disengage but
there is no way to find out.

On 2007-11-20 15:49:16 -0500, Wayne.B said:

On Tue, 20 Nov 2007 12:22:40 -0500, Martin Baxter
wrote:

Forgive my ignorance, I'm just not familiar with something this big. I
would think that you could just leave the tranny in gear and stop the
motor, or is there sufficient torque generated to turn the motor over?

The tranny is hydraulically actuated internally with its own pump
driven by the engine. With the engine off there is no pressure to keep
the clutches engaged. As long as the transmission is in gear however,
it is impossible to shut the engine down because of the prop rotation
being passed through. It's quite possible that there would be enough
torque to restart the engine if it did not disengage but there is no
way to find out.

I've always wondered... Why not put a feathering prop on at least one
of the shafts? Yeah, I know they're expen$ive (we have a MaxProp), but
it seems like it might be overall cheaper in the long run.

Then again, I'm not sure I've seen a 30" feathering prop. Nevermind....
MaxProp show up to 44" and some indication of a 4 blade; Autoprop shows
up to 36". Dang, I'd hate to pay their cost, but I don't much like
buying fuel or transmissions either.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

On Wed, 21 Nov 2007 00:46:44 GMT, Jere Lull wrote:

I've always wondered... Why not put a feathering prop on at least one
of the shafts? Yeah, I know they're expen$ive (we have a MaxProp), but
it seems like it might be overall cheaper in the long run.

Then again, I'm not sure I've seen a 30" feathering prop. Nevermind....
MaxProp show up to 44" and some indication of a 4 blade; Autoprop shows
up to 36". Dang, I'd hate to pay their cost, but I don't much like
buying fuel or transmissions either.

It's a good thought and one that I might consider if I have to reprop
again sometime in the future. Do you have any idea how they work? Is
the pitch adjustable in some way or do they just self-feather from the
force of the water like a folding prop?

The other important issue is reliability. If you are docking a 60,000
lb boat in close quarters you *really* want to know that forward and
reverse are working exactly as planned. There is no fending off by
hand if something goes wrong. The reality of today's boat insurance
market is that if you have an expensive liability claim from damage to
another boat, you are probably going to get cancelled and have trouble
finding another policy. You pretty much have to self insure for all
but the very largest losses these days.