RG wrote:
On another thread, I asked about a 2 stroke vs. a 4 stroke for flats
fishing. Lots of "up on plane, get going .. stop .. do it again" etc. I run
in 18 inches of water or less most of the time.

One respondent brings up the theory that "four strokes can and do produce
better "thrust"". Is that theory correct?

In my original posting, I clearly needed/want hole shot..not better gas
mileage..more quiet..less pollution, or top end speed. Right now, in the
couple of groups in which I posted the original question...the vote is 27 to
3 votes in favor of 2 stokes over 4 strokes??????. If his theory is
correct...the 27 to 3 seems wrong for my particular needs. any comments are
much appreciated.. thanks



Not really the thrust is a function of the propeller & what type of
engine turns it. Propellers with lost of pitch to provide a high top
speed on a fast boat, need lots of low down torque to get them away
quickly from a standing start. What you really want is an engine with
the best low down torque & traditionally 4 strokes have been good at
this, however this is not the case with the new 4 stroke OBs.

It's true 4 strokes can produce good torque however in your hole shot
premises a 2 stroke can be just as good & sometimes better (more bangs
for a given number of prop turns). So the 2 strokes can produce good low
down torque which means they can bog less from a standing start, this is
usually put down to their weight advantage but.

The new 4 strokes are usually very high revving engines (sometimes
higher than the equivalent HP 2 stroke) which means they produce their
best torque quite high up the rev band, again contrary to the usual
comments.

For getting away quickly the 2 strokes are OK indeed that's probably
their only strong point, but for fuel economy, long service life, ease
of use, resale value etc the 4 stroke is the go.

You've been warned about the Evinrudes, stay well away for the next 5
yrs at least, indeed I'll predict they won't even exist in 5 yrs just as
I did Ficht & it only took 3 yrs for them to go:-).


K

For getting away quickly the 2 strokes are OK indeed that's probably
their only strong point, but for fuel economy, long service life,

Large 2 stroke OB's have demonstrated their ability to provide a long
reliable service life over several decades, large 4 stroke OB's have not.

/nods

I know of *many* two-stoke outboards that have several decades on individual
units.

If the 4 stroke outboards turn out anything like the 4 stroke motorcycle
engines. They won't have as long a service life.

-W

"-v-" wrote in message
...
For getting away quickly the 2 strokes are OK indeed that's probably
their only strong point, but for fuel economy, long service life,

Large 2 stroke OB's have demonstrated their ability to provide a long
reliable service life over several decades, large 4 stroke OB's have not.

Clams Canino wrote:
/nods

I know of *many* two-stoke outboards that have several decades on individual
units.

If the 4 stroke outboards turn out anything like the 4 stroke motorcycle
engines. They won't have as long a service life.

-W

"-v-" wrote in message
...

For getting away quickly the 2 strokes are OK indeed that's probably
their only strong point, but for fuel economy, long service life,

Large 2 stroke OB's have demonstrated their ability to provide a long
reliable service life over several decades, large 4 stroke OB's have not.






Touche!!! Point taken from you both & begrudgingly accepted:-)


K

So...if you want to play with TC-3 oil, snort oil fumes, sacrifice
fuel mileage, and endure the noise for a superior hole shot, the 27 to
3 vote is probably right on target. You'll be much happier with the 2
stroke.

I don't get it, but different strokes for different folks.....

--



Grady-White Gulfstream, out of Southport, NC.

http://myworkshop.idleplay.net/cavern/ Homepage
http://www.southharbourvillage.com/directions.asp Where Southport,NC
is located.
http://www.southharbourvillage.com/autoupdater.htm Real Time Pictures at
My Marina
http://www.thebayguide.com/rec.boats Rec.boats at
Lee Yeaton's Bayguide










Everyone in the marine industry and most of its environmental critics are aware
that there are now at least four manufacturers of two-cycle outboards with DFI,
direct fuel injection: systems that put the fuel directly into the combustion
chamber after the intake and exhaust ports close. Such systems eliminate loss
of some of the incoming fuel charge out the exhaust ports along with the
scavenged products of combustion that occurs with carbureted or EFI manifold
injection systems. Nevertheless, conventional wisdom tells most of the critics
of the two-cycle engine that it will never be as clean as a four-cycle engine.
For this reason they would eventually advocate banning the two-cycle engine
from the waterways on environmental protection grounds.

There are even more manufacturers producing four-cycle outboards, including the
same manufacturers that make the DFI two-cycle engines. They must seemingly
follow down both roads for self preservation, as part of the outboard market is
definitely leaning in the four-cycle direction, driven that way by hype,
environmental concerns, and certain perceived advantages. We have already
considered the ramifications of the increased engine weight for the
four-cycles, the potential effect on boat trim, and the possible inability to
float the boat level when swamped, as required by federal regulations for
outboard boats less than 20-feet long. Then there is also the increased cost
and complexity involved with four-cycle power, to be offset by savings realized
in fuel consumed and elimination of smoke and oil slicks.

This may be the price of progress, they say. But, is it possible to "have your
cake and eat it, too?" Some recent tests run comparing 2002 model two-cycle DFI
outboards with four-cycle outboards of equal power rating, mounted on the same
boat, would seem to indicate such things are really possible. Comparison tests
of two brands of four-cycle 225-hp outboards were made with a current state-of
the-art DFI two-cycle 225. On identical 20'7" boats one four-cycle brand
produced a best mileage of 4.7 mpg at 27.7 mph while the two-cycle gave a best
4.5 mpg at 28.6 mph. Very close. But, the two-cycle had a top speed of 59.8 mph
against 52.4 mph for the four-cycle. At the same 52-mph speed the two-cycle
gave better mileage to the tune of 3.2 mpg to 2.7 mpg for the four-cycle. The
two-cycle produced better fuel mileage at every speed from 34 mph up and was
also better at trolling speeds of 4-7 mph.

When tested against the other 225-hp, four-cycle brand on identical 24' boats,
the DFI two-cycle again prevailed overall, delivering a matching best 3.15 mpg
at 32 mph. This outran the four-cycle 49.3 to 45.7 mph, getting better mileage
(2.58 mpg) at its top speed than the four-cycle (2.44 mpg) at its top speed. It
also produced far better mileage in the trolling speed range from 3.5-8 mph.

A third set of tests compared a 135-hp, two-cycle DFI outboard against a
130-hp, four-cycle outboard on identical 20' boats. The two-cycle delivered
4.25 mpg at 20.8 mph against a best 3.97 mpg at 20.4 mph for the four-cycle.
Best economy for the two-cycle was achieved at 27.9 mph: 4.45 mpg. It also
bested the four-cycle in the 3-8 mph trolling speed range and beat it in top
speed 43 mph/3.54 mpg to 37 mph/2.97 mpg.

"Bah, humbug!" you might say. But there are sound engineering internal
combustion engine principles for this surprising result. It is true that the
typical four-cycle engine may have an inherent advantage in fuel consumed per
horsepower. But not when the engine must be designed to produce very high
horsepower per cubic inch of displacement at high engine speeds, as it must to
achieve even the already heavier weight seen when compared to its two-cycle
competitor.

In order to achieve this high-power output, while firing only every other
revolution of the crankshaft, the camshaft valve timing must develop
considerable overlap between intake and exhaust valve openings and closings,
which means it begins to suffer some of the same raw fuel loss out the exhaust
problems as the carbureted or manifold injected two-cycle engine. It only has
manifold injection, so the fuel and air must mix in the manifold and enter
together past the intake valve into the combustion chamber while the exhaust
valve is still partly open. The result is Some loss in fuel economy.

Since the four-cycle engine has the same radical valve timing at low engine
speeds, it suffers even more when compared to the two-cycle DFI engine at
trolling speeds. The only way to fix this problem in the four-cycle engine is
to go to direct fuel injection into the combustion chamber after the valves
close, like the DFI two-cycle, or have a system providing variable valve timing
with engine speed, conservative timing at lower speed and radical timing at
higher speed. Such systems are now being developed for future automobile
engines. Such things would add complexity, cost and weight, to an already more
expensive and heavier product.

Then there is the factor of acceleration from idle to planing speed. On the 241
boat the 225-hp, two-cycle DFI went from zero to 150 feet in 7.06 seconds while
the four-cycle took 7.76 seconds. On the 20' boat the 135-hp, two-cycle DFI
went zero to 150 feet in 6.2 seconds while the four-cycle took 8.7 seconds for
the same distance. Acceleration from zero to 30 mph on the 20'7" boat for the
225-hp two-cycle DFI took 5.77 seconds compared to 10.7 seconds for the 225-hp
four cycle. This demonstrates the better low-end torque and fast-rising power
curve of the two-cycle, firing every revolution of the crankshaft. The
four-cycles are quieter at low engine speeds, but this advantage goes away at
the higher engine speeds.

So, the conclusions are that the state of the art two-cycle DFI outboard can
match or beat the four-cycle in fuel economy, top speed, and acceleration. What
about exhaust emissions, which brought on the whole move to four-cycle
outboards in the first place? These two-cycle engines can match or beat the
four-cycles there, as well. It matches pretty much with the fuel economy story.
The more fuel the engine consumes at a given boat speed, the more exhaust
emissions that come out the other end. With precise microprocessor control and
direct injection of the fuel into the combustion chamber after the ports close,
the two-cycle DFI can better the most stringent exhaust emission requirements
now proposed out to 2007. The four-cycle can do no better.

After more than five years of testing and field experience the 2002 two-cycle
DFI outboards have been developed to have quality durability, economy and
environmental friendliness to match or beat the four-cycles, and at lower
weight and cost. Both can exist and be successful in the marine market but no
one should sell the two-cycle engine short on its ability to survive and
prosper long into the future. It just has too many good things going for it.
You might even see it on some future stern drives.

Ralph Lambrecht is an engineer with more than 50 years of experience in the
marine industry and marine safety standards development.

Lambrecht, Ralph. 2002. “Two-stroke conventional wisdom.� Boat & Motor
Dealer. April. 34-37

On Tue, 09 Dec 2003 02:33:31 +0000, F330 GT wrote:

So...if you want to play with TC-3 oil, snort oil fumes, sacrifice
fuel mileage, and endure the noise for a superior hole shot, the 27 to
3 vote is probably right on target. You'll be much happier with the 2
stroke.

I don't get it, but different strokes for different folks.....


Everyone in the marine industry and most of its environmental critics are aware
that there are now at least four manufacturers of two-cycle outboards with DFI,
direct fuel injection: systems that put the fuel directly into the combustion
chamber after the intake and exhaust ports close.

Some interesting data. But I'm confused. If the fuel is injected directly
into the combustion chamber (and I assume immediately burned), how does
the crankcase get lubricated? Is there oil in the "fuel" that's injected?
Why?

Now, you say a DFI 2-stroke has better emissions than a 4-stroke. I infer
that you're talking about a carburated 4-stroke - what about a DFI
4-stroke (like most 4-stroke motorbike engines are, I believe)? As long as
a 2-stoke burns oil, I can't see how it will do better, emission-wise,
than a comparable 4-stroke (ie carb-to-carb, DFI-to-DFI, etc).

And, again by experience: I have yet to see a 2-stroke outboard that
doesn't smoke like hell at idle. And I see a lot of outboards at launch
ramps, marinas, etc. Maybe nobody's buying these DFI outboards?

Lloyd Sumpter
"Far Cove" Catalina 36

Lloyd Sumpter wrote:
On Tue, 09 Dec 2003 02:33:31 +0000, F330 GT wrote:


So...if you want to play with TC-3 oil, snort oil fumes, sacrifice
fuel mileage, and endure the noise for a superior hole shot, the 27 to
3 vote is probably right on target. You'll be much happier with the 2
stroke.

I don't get it, but different strokes for different folks.....


Everyone in the marine industry and most of its environmental critics are aware
that there are now at least four manufacturers of two-cycle outboards with DFI,
direct fuel injection: systems that put the fuel directly into the combustion
chamber after the intake and exhaust ports close.


Some interesting data. But I'm confused. If the fuel is injected directly
into the combustion chamber (and I assume immediately burned), how does
the crankcase get lubricated?

By tiny amounts of oil being directly inject into it below (actually
through the bore at the piston's side) the piston, raw oil with no fuel
(some of the DFIs have an even tinier amount of oil mixed in the fuel
but this is just to lubricate the injection system/pump itself)

Is there oil in the "fuel" that's injected?
Why?

Save mentioned; no none to lubricate the engine itself.


Now, you say a DFI 2-stroke has better emissions than a 4-stroke. I infer
that you're talking about a carburated 4-stroke - what about a DFI
4-stroke (like most 4-stroke motorbike engines are, I believe)?

No the 4 strokes are mostly EFI not DFI. There are a couple of DFI 4
strokes, Mitsubishi has been playing with it & also Mercedes but so far
it's been shown not to be worth the extra trouble & causes new problems,
EPA & power wise.

As long as
a 2-stoke burns oil, I can't see how it will do better, emission-wise,
than a comparable 4-stroke (ie carb-to-carb, DFI-to-DFI, etc).

They only inject a tiny amount in the crankcase of the DFI, even less
with the latest consumer funded experiment called E-tech (ficht in
drag:-)) The "claim" (probably false yet again) that running hour for
running hour they'll use less oil that the 4 strokes (change intervals)

And, again by experience: I have yet to see a 2-stroke outboard that
doesn't smoke like hell at idle. And I see a lot of outboards at launch
ramps, marinas, etc. Maybe nobody's buying these DFI outboards?

No nobody who has made any sort of independent enquiries. They run very
lean mixtures at low revs to get through the EPA & so they heat the
pistons with abnormal combustion when lean, when the engine is returned
to "normal" mixtures & power is increased the pistons are hot enough to
provoke uncontrolled detonation & failure. OMC itself admitted to a 1 in
5 failure rate & none of the so called fixes including the latest, has
addressed the core issues. Their latest joke is stronger pistons!!! It'd
be funny were it not consumers paying for this BS.

Don't buy evinrude not ever, they're rude!!!

K

See remembered no Harry paste:-)


Lloyd Sumpter
"Far Cove" Catalina 36

"K Smith" wrote in message
...
Clams Canino wrote:
/nods

I know of *many* two-stoke outboards that have several decades on
individual
units.

If the 4 stroke outboards turn out anything like the 4 stroke
motorcycle
engines. They won't have as long a service life.

-W

"-v-" wrote in message
...

For getting away quickly the 2 strokes are OK indeed that's
probably
their only strong point, but for fuel economy, long service life,

Large 2 stroke OB's have demonstrated their ability to provide a
long
reliable service life over several decades, large 4 stroke OB's have
not.






Touche!!! Point taken from you both & begrudgingly accepted:-)


K

You might want to check out the Bass and Walleye boats page to see if
they have any comparisons on line. And keep in mind that it won't be
long and you won't be able to buy (new anyway) any of those fine
carburated 2 strokes that have demonstrated reliability, only 4 strokes
or DFI. Now which of those have the best reliabilty. And I don't know
where you got the idea that 2 stroke MC engines were more durable than 4
strokes.

del cecchi

del cecchi wrote:
"K Smith" wrote in message
...

Clams Canino wrote:

/nods

I know of *many* two-stoke outboards that have several decades on

individual

units.

If the 4 stroke outboards turn out anything like the 4 stroke

motorcycle

engines. They won't have as long a service life.

-W

"-v-" wrote in message
. com...


For getting away quickly the 2 strokes are OK indeed that's

probably

their only strong point, but for fuel economy, long service life,

Large 2 stroke OB's have demonstrated their ability to provide a

long

reliable service life over several decades, large 4 stroke OB's have

not.




Touche!!! Point taken from you both & begrudgingly accepted:-)


K


You might want to check out the Bass and Walleye boats page to see if
they have any comparisons on line. And keep in mind that it won't be
long and you won't be able to buy (new anyway) any of those fine
carburated 2 strokes that have demonstrated reliability, only 4 strokes
or DFI. Now which of those have the best reliabilty. And I don't know
where you got the idea that 2 stroke MC engines were more durable than 4
strokes.

del cecchi


Sadly true about not being "able" to get a simple carbed 2 stroke, but
like the cars in the 70s doom & gloom prevailed over the CA CARB regs
however in the end we have better cars, same will happen with 4 stroke
OBs I'd suggest. The DFIs were a passing thing that have done most of
their damage, save a few diehards like Bill, but they're dead & have
been from the beginning.

I do think Clams & V make a point though, it's still too early to say
for absolutely sure the 4 strokes will last as long as the old tech 2
strokes.


K

I didn't - I commented that 4 cycle MC engines were not that durable - at
least as compared to car engines. If the 4 cycle outboards run 'em like a
bike engine.....

-W

"del cecchi" wrote in message news:fUbBb.836

And I don't know
where you got the idea that 2 stroke MC engines were more durable than 4
strokes.

del cecchi