Running a large gasoline engine at low RPM for long periods
 

I have a boat with twin 350 hp Crusader gas engines. I would like to
cruise this boat between Florida and the Bahamas. It will be optimal
for me to cross the Gulf Stream at high cruising speeds to get out of
harms way, then reduce to a very slow speed when moving around the
islands in order to conserve fuel and increase my range. I've heard
that this can cause fouling of spark plugs. Has anyone tried this and
can comment on doing something like this? Does the plug fouling
happen over a lengthy period of time (weeks) or rather quickly (hours)?

Running a large gasoline engine at low RPM for long periods
 

What do you mean by slow speeds? Is this a planing boat or a displacement
boat? Generally it is considered bad for gasoline engines to idle them for
extended periods. If the carbs are set up properly though it should not
foul the plugs very much. You can speed up for a few minutes occasionally
to clean them out. I don't think you are really going to find idling around
in a planing boat to be very satisfactory. You might experiment with
running on one engine to see if you can achieve the low speed you want with
the endgine running above idle.

"Diego" wrote in message
ups.com...
I have a boat with twin 350 hp Crusader gas engines. I would like to
cruise this boat between Florida and the Bahamas. It will be optimal
for me to cross the Gulf Stream at high cruising speeds to get out of
harms way, then reduce to a very slow speed when moving around the
islands in order to conserve fuel and increase my range. I've heard
that this can cause fouling of spark plugs. Has anyone tried this and
can comment on doing something like this? Does the plug fouling
happen over a lengthy period of time (weeks) or rather quickly (hours)?

Running a large gasoline engine at low RPM for long periods
 

Here's a good link http://www.boatdocking.com/other/Mushing.html

"Diego" wrote in message
ups.com...
I have a boat with twin 350 hp Crusader gas engines. I would like to
cruise this boat between Florida and the Bahamas. It will be optimal
for me to cross the Gulf Stream at high cruising speeds to get out of
harms way, then reduce to a very slow speed when moving around the
islands in order to conserve fuel and increase my range. I've heard
that this can cause fouling of spark plugs. Has anyone tried this and
can comment on doing something like this? Does the plug fouling
happen over a lengthy period of time (weeks) or rather quickly (hours)?

Running a large gasoline engine at low RPM for long periods
 

"jamesgangnc" wrote in message
...
Here's a good link http://www.boatdocking.com/other/Mushing.html

"Diego" wrote in message
ups.com...
I have a boat with twin 350 hp Crusader gas engines. I would like to
cruise this boat between Florida and the Bahamas. It will be optimal
for me to cross the Gulf Stream at high cruising speeds to get out of
harms way, then reduce to a very slow speed when moving around the
islands in order to conserve fuel and increase my range. I've heard
that this can cause fouling of spark plugs. Has anyone tried this and
can comment on doing something like this? Does the plug fouling
happen over a lengthy period of time (weeks) or rather quickly (hours)?




Charles Low used to be a regular contributor here. Haven't seen his name
for a while.
All around good guy.

Eisboch

Running a large gasoline engine at low RPM for long periods
 

"Eisboch" wrote
http://www.boatdocking.com/other/Mushing.html
Charles Low used to be a regular contributor here. Haven't seen his name
for a while.
All around good guy.

Good writer, too. I enjoyed the article. Maybe even learned something.

Running a large gasoline engine at low RPM for long periods
 

Running a large gasoline engine at low RPM for long periods
 

Running a large gasoline engine at low RPM for long periods
 

On Sep 29, 12:46 pm, trainfan1 wrote:
wrote:
On Fri, 28 Sep 2007 13:29:04 -0700, Diego wrote:

I have a boat with twin 350 hp Crusader gas engines. I would like to
cruise this boat between Florida and the Bahamas. It will be optimal
for me to cross the Gulf Stream at high cruising speeds to get out of
harms way, then reduce to a very slow speed when moving around the
islands in order to conserve fuel and increase my range. I've heard
that this can cause fouling of spark plugs. Has anyone tried this and
can comment on doing something like this? Does the plug fouling
happen over a lengthy period of time (weeks) or rather quickly (hours)?

Any fairly modern engine will be fine going slow...
2 strokes have a
problem with this for a number of reasons but 4 strokes don't share
those problems.

Unless it's an E-Tec or Optimax.

A port or direct fuel injected inboard engine should do fine
indefinitely. A carbed or CFI engine may suffer from fuel pooling &
sporadic rich operation(fouling the plugs), especially high performance
engines. If intake charge velocity is maintained, by design or by
engine speed, prolonged idling should pose no problem.

A 350 hp Crusader should be a 454 Chevy(maybe 496 CID if newer), it
should do fine idling, even with carbs.

Rob- Hide quoted text -

- Show quoted text -

AAgreed. If anything edse, and if it they arn't already, I'd change
them over from points ignition to electronic. Can be done simply too.
Pertronix ovvers a "drop-in kit for less than $100.00 each that is
simple to install with no modifications to the distributors. No need
to pull the distributors either.

The advantage is a much higher spark voltage which increases fuel burn
efficiency, and plug life.

Running a large gasoline engine at low RPM for long periods
 

Common misconception about ignitions. If the spark is igniting the fuel it
can't ingnite it "better". Nor does the spark clean the plug, the fuel
combustion does that. The temp of a plug is primarily about how far into
the combustion chamber it protrudes.

"Tim" wrote in message
oups.com...
On Sep 29, 12:46 pm, trainfan1 wrote:
wrote:
On Fri, 28 Sep 2007 13:29:04 -0700, Diego wrote:

I have a boat with twin 350 hp Crusader gas engines. I would like to
cruise this boat between Florida and the Bahamas. It will be optimal
for me to cross the Gulf Stream at high cruising speeds to get out of
harms way, then reduce to a very slow speed when moving around the
islands in order to conserve fuel and increase my range. I've heard
that this can cause fouling of spark plugs. Has anyone tried this and
can comment on doing something like this? Does the plug fouling
happen over a lengthy period of time (weeks) or rather quickly
(hours)?

Any fairly modern engine will be fine going slow...
2 strokes have a
problem with this for a number of reasons but 4 strokes don't share
those problems.

Unless it's an E-Tec or Optimax.

A port or direct fuel injected inboard engine should do fine
indefinitely. A carbed or CFI engine may suffer from fuel pooling &
sporadic rich operation(fouling the plugs), especially high performance
engines. If intake charge velocity is maintained, by design or by
engine speed, prolonged idling should pose no problem.

A 350 hp Crusader should be a 454 Chevy(maybe 496 CID if newer), it
should do fine idling, even with carbs.

Rob- Hide quoted text -

- Show quoted text -

AAgreed. If anything edse, and if it they arn't already, I'd change
them over from points ignition to electronic. Can be done simply too.
Pertronix ovvers a "drop-in kit for less than $100.00 each that is
simple to install with no modifications to the distributors. No need
to pull the distributors either.

The advantage is a much higher spark voltage which increases fuel burn
efficiency, and plug life.

Running a large gasoline engine at low RPM for long periods
 

"Diego" wrote
reduce to a very slow speed when moving around the
islands in order to conserve fuel and increase my range.

I once made a 50 mile round trip with a Merc 165 at idle and occasionally
just a tick over. Maybe 1000 RPM during the periods I was hurrying. No
problems at all with the 30 year-old carbureted breaker point engine. Took
about 12 hours and used only a little less fuel than the same trip at a
moderate planing cruise. At the time I was less interested in miles than I
was in time-on-water per gallon, if you know what I mean.

Running a large gasoline engine at low RPM for long periods
 

On Sep 29, 1:27 pm, "jamesgangnc" wrote:
Common misconception about ignitions. If the spark is igniting the fuel it
can't ingnite it "better". Nor does the spark clean the plug, the fuel
combustion does that. The temp of a plug is primarily about how far into
the combustion chamber it protrudes.


Actually james, i could almost agree with you, but I was'nt aproaching
the idea of a hotter/colder plug. Just hotter (quicker) spark, which
enhances spark plug life. (Higher volts/less amps)

The 40,000+ volts to the plugs (HEI) is more efficient than the old
12-14,000 volts (points). otherwise GM should have left well enough
alone (points) in 1974. When they introduced HEI, spark plug life
increased dramatically about 500% not counting less oil and fuel
fouling. Of course HEI allowed OEM's to use plugs with a wider gap
thus getting a faster fire rate.

20 yrs ago, I ahd a really nice '69 Pontiac grand prix. 400 cid 4 bbl.
I pulled the points distributor and installed an HEI from a 1975.
Performance, fuel economy, and plug life increased.

Of course YMMV.




"Tim" wrote in message

oups.com...



On Sep 29, 12:46 pm, trainfan1 wrote:
wrote:
On Fri, 28 Sep 2007 13:29:04 -0700, Diego wrote:

I have a boat with twin 350 hp Crusader gas engines. I would like to
cruise this boat between Florida and the Bahamas. It will be optimal
for me to cross the Gulf Stream at high cruising speeds to get out of
harms way, then reduce to a very slow speed when moving around the
islands in order to conserve fuel and increase my range. I've heard
that this can cause fouling of spark plugs. Has anyone tried this and
can comment on doing something like this? Does the plug fouling
happen over a lengthy period of time (weeks) or rather quickly
(hours)?

Any fairly modern engine will be fine going slow...
2 strokes have a
problem with this for a number of reasons but 4 strokes don't share
those problems.

Unless it's an E-Tec or Optimax.

A port or direct fuel injected inboard engine should do fine
indefinitely. A carbed or CFI engine may suffer from fuel pooling &
sporadic rich operation(fouling the plugs), especially high performance
engines. If intake charge velocity is maintained, by design or by
engine speed, prolonged idling should pose no problem.

A 350 hp Crusader should be a 454 Chevy(maybe 496 CID if newer), it
should do fine idling, even with carbs.

Rob- Hide quoted text -

- Show quoted text -

AAgreed. If anything edse, and if it they arn't already, I'd change
them over from points ignition to electronic. Can be done simply too.
Pertronix ovvers a "drop-in kit for less than $100.00 each that is
simple to install with no modifications to the distributors. No need
to pull the distributors either.

The advantage is a much higher spark voltage which increases fuel burn
efficiency, and plug life.- Hide quoted text -

- Show quoted text -

Running a large gasoline engine at low RPM for long periods
 

Unless it's an E-Tec or Optimax.

A port or direct fuel injected inboard engine should do fine
indefinitely. A carbed or CFI engine may suffer from fuel pooling &
sporadic rich operation(fouling the plugs), especially high performance
engines. If intake charge velocity is maintained, by design or by
engine speed, prolonged idling should pose no problem.

A 350 hp Crusader should be a 454 Chevy(maybe 496 CID if newer), it
should do fine idling, even with carbs.

Rob


Thank you all for your comments. Lots of useful information. Rob,
you're correct, it is a 454 Chevy, but an older carbed engine.