On Mon, 23 Feb 2004 23:22:55 GMT, "Rich" wrote:


"Wayne.B" wrote in message
.. .
160 is OK for fresh water usage but not for salt water.


Why is that?
=========================================

Salt begins to precipitate out of solution as temperatures increase
and will cause clogged cooling passages.

If this were true, there would be no need for a choke
on a carbed engine.

Short Wave Sportfishing wrote:

On Mon, 23 Feb 2004 20:10:04 GMT, "Geoff 93 RRC"
wrote:

It seems most new boats have a 160 thermostat these days. I have a '93
Mercruiser 4.3LX. Can I use the 160 thermostat? I boat exclusively in
fresh water. I want to get the cleaner combustion that the higher temps
give.

Ok, I've a different opinion.

I prefer to run a little cooler thermostat with a hotter plug. I've
done this on my antigue trucks and this technique works great.

If you are looking for power and clean combustion, a hotter plug is
always the best choice over fooling around with the thermostat. You
have to remember that the reason you have a thermostat is to maintain
a constant temperature on the block for expansion/contraction reasons
- not for combustion. Combustion is strictly the pervue of how hot
the spark is.

Curiosity question - raw water cooled or fresh.

Later,

Tom
S. Woodstock, CT
----------

Basic Fishing Program:

10 - Fish
20 - Eat
30 - Sleep
40 - Goto 10

"Geoff 93 RRC" wrote in message
m...
It seems most new boats have a 160 thermostat these days. I have a '93
Mercruiser 4.3LX. Can I use the 160 thermostat?


You probably would not notice a difference in engine performance or
efficiency during normal boating operation. MercCruiser uses a 140 degree
thermostat in the same 4.3 engine that Volvo and the former OMC use with a
160 degree version.

Bill Grannis
service manager

The boat is fresh water cooled. What hotter range plug would you recommend
and how much hotter is it than the standard plug?

Thanks,
Geoff

"Short Wave Sportfishing" wrote in message
...
On Mon, 23 Feb 2004 20:10:04 GMT, "Geoff 93 RRC"
wrote:

It seems most new boats have a 160 thermostat these days. I have a '93
Mercruiser 4.3LX. Can I use the 160 thermostat? I boat exclusively in
fresh water. I want to get the cleaner combustion that the higher temps
give.

Ok, I've a different opinion.

I prefer to run a little cooler thermostat with a hotter plug. I've
done this on my antigue trucks and this technique works great.

If you are looking for power and clean combustion, a hotter plug is
always the best choice over fooling around with the thermostat. You
have to remember that the reason you have a thermostat is to maintain
a constant temperature on the block for expansion/contraction reasons
- not for combustion. Combustion is strictly the pervue of how hot
the spark is.

Curiosity question - raw water cooled or fresh.

Later,

Tom
S. Woodstock, CT
----------

Basic Fishing Program:

10 - Fish
20 - Eat
30 - Sleep
40 - Goto 10

Woops, I meant raw water cooled - no heat exchanger. I think I am sticking
with the cooler 143 degree thermostat. We boat on Lake Travis in Austin, TX
and although very clean, its "hard" water. I have the scale on my outdrive
to prove it. Seems the cooler running temps will limit mineral precipation
as it does for sea salt.

Thanks for all of the replies.

"Geoff 93 RRC" wrote in message
m...
The boat is fresh water cooled. What hotter range plug would you
recommend
and how much hotter is it than the standard plug?

Thanks,
Geoff

"Short Wave Sportfishing" wrote in
message
...
On Mon, 23 Feb 2004 20:10:04 GMT, "Geoff 93 RRC"
wrote:

It seems most new boats have a 160 thermostat these days. I have a '93
Mercruiser 4.3LX. Can I use the 160 thermostat? I boat exclusively in
fresh water. I want to get the cleaner combustion that the higher
temps
give.

Ok, I've a different opinion.

I prefer to run a little cooler thermostat with a hotter plug. I've
done this on my antigue trucks and this technique works great.

If you are looking for power and clean combustion, a hotter plug is
always the best choice over fooling around with the thermostat. You
have to remember that the reason you have a thermostat is to maintain
a constant temperature on the block for expansion/contraction reasons
- not for combustion. Combustion is strictly the pervue of how hot
the spark is.

Curiosity question - raw water cooled or fresh.

Later,

Tom
S. Woodstock, CT
----------

Basic Fishing Program:

10 - Fish
20 - Eat
30 - Sleep
40 - Goto 10

On Tue, 24 Feb 2004 02:36:53 GMT, Jim Kelly wrote:

If this were true, there would be no need for a choke
on a carbed engine.

Huh?

What does choking an engine (limiting the air in the fuel mixture for
a quicker start) have to do with hot plugs?

Just curious.

Later,

Tom
S. Woodstock, CT
----------

Basic Fishing Program:

10 - Fish
20 - Eat
30 - Sleep
40 - Goto 10

I am questioning your assertion that "combustion is strictly the pervue
of how hot the spark is." I contend that that it is necessary to
increase the fuel to air ratio on a cold engine because the engine is not
imparting enough heat to the mix to create a combustible mix regardless
of the heat range of the plug. Therefore, engine temperature has a
direct effect on combustion.

I agree with your contention that mechanical clearances in the engine are
designed around a certain operating temperature. If the engine is
operating above or below the design temperature, thermal expansion rates
of the materials in the engine will result in clearances that are
different than the design criteria.

Short Wave Sportfishing wrote:

On Tue, 24 Feb 2004 02:36:53 GMT, Jim Kelly wrote:

If this were true, there would be no need for a choke
on a carbed engine.

Huh?

What does choking an engine (limiting the air in the fuel mixture for
a quicker start) have to do with hot plugs?

Just curious.

Later,

Tom
S. Woodstock, CT
----------

Basic Fishing Program:

10 - Fish
20 - Eat
30 - Sleep
40 - Goto 10

On Wed, 25 Feb 2004 02:01:22 GMT, Jim Kelly wrote:

I am questioning your assertion that "combustion is strictly the pervue
of how hot the spark is." I contend that that it is necessary to
increase the fuel to air ratio on a cold engine because the engine is not
imparting enough heat to the mix to create a combustible mix regardless
of the heat range of the plug. Therefore, engine temperature has a
direct effect on combustion.

I can agree with that. However, combustion has to be initiated by the
spark. The fact that a cylinder is operating at certain temperature
only assures that the fuel/air mix on entering the chamber is fairly
evenly dispursed. The source of ignition is still the spark. A
hotter spark means that more energy is imparted to the explosive
mixture resulting in a cleaner burn with more energy transfer. The
gas expansion rate is better because the burn is initiated quicker.

Additionally, a hotter plug in a cold normally aspirated engine means
that one can use less choke on starting. Faster start, faster warm
up.

Later,

Tom
S. Woodstock, CT
----------

Basic Fishing Program:

10 - Fish
20 - Eat
30 - Sleep
40 - Goto 10

"Short Wave Sportfishing" wrote in message
...
On Wed, 25 Feb 2004 02:01:22 GMT, Jim Kelly wrote:

I am questioning your assertion that "combustion is strictly the pervue
of how hot the spark is." I contend that that it is necessary to
increase the fuel to air ratio on a cold engine because the engine is not
imparting enough heat to the mix to create a combustible mix regardless
of the heat range of the plug. Therefore, engine temperature has a
direct effect on combustion.

I can agree with that. However, combustion has to be initiated by the
spark. The fact that a cylinder is operating at certain temperature
only assures that the fuel/air mix on entering the chamber is fairly
evenly dispursed. The source of ignition is still the spark. A
hotter spark means that more energy is imparted to the explosive
mixture resulting in a cleaner burn with more energy transfer. The
gas expansion rate is better because the burn is initiated quicker.

Additionally, a hotter plug in a cold normally aspirated engine means
that one can use less choke on starting. Faster start, faster warm
up.

Later,

Tom
S. Woodstock, CT
----------

Basic Fishing Program:

10 - Fish
20 - Eat
30 - Sleep
40 - Goto 10


Wrong! A hotter plug only keeps you from fouling at the temperature you are
running. No hotter spark. Same coil and ignition driving the EMF. Same
gap normally. A hotter plug, just does not transfer as much heat in the
same time as cold plug. The heat is transferred to the head and cooling
system. If you are running a cold engine, the burn is not as complete and
with a normal heat range plug, it would foul and not fire. The hotter range
plug just allows the carbon to burn off. Ideal would be a ceramic engine,
that allows you run real high temps with out melting the piston, etc. Could
get even more energy out of the gallon of gas. When starting, all the plugs
are cold. More gas as the volatility of the fuel, does not allow as much
vapor to ignite, so more fuel == more vapor. Why you get lots of carbon
(black smoke) out the tail pipe on an engine with a stuck choke.

But the heat range of the plug is only a function of the heat transfer rate of
the insulator. Hotter plugs have a longer path from the tip to the metal body
which transfers the heat to the head. So the tip of a hotter plug wood
maintain a higher temperature. However, any plug capable of igniting
combustion will create the same reaction in the combustion chamber and deliver
the same amount of power. A hotter plug may have less of a tendency to foul
if this is a problem.

Short Wave Sportfishing wrote:

On Wed, 25 Feb 2004 02:01:22 GMT, Jim Kelly wrote:

I am questioning your assertion that "combustion is strictly the pervue
of how hot the spark is." I contend that that it is necessary to
increase the fuel to air ratio on a cold engine because the engine is not
imparting enough heat to the mix to create a combustible mix regardless
of the heat range of the plug. Therefore, engine temperature has a
direct effect on combustion.

I can agree with that. However, combustion has to be initiated by the
spark. The fact that a cylinder is operating at certain temperature
only assures that the fuel/air mix on entering the chamber is fairly
evenly dispursed. The source of ignition is still the spark. A
hotter spark means that more energy is imparted to the explosive
mixture resulting in a cleaner burn with more energy transfer. The
gas expansion rate is better because the burn is initiated quicker.

Additionally, a hotter plug in a cold normally aspirated engine means
that one can use less choke on starting. Faster start, faster warm
up.

Later,

Tom
S. Woodstock, CT
----------

Basic Fishing Program:

10 - Fish
20 - Eat
30 - Sleep
40 - Goto 10