Dave: No comments from the peanut gallery.

I'm using the term "speedboats" to describe boats which sound like they have
(and probably do have) a pair of 400+ cubic inch motors in the back? In
order to achieve their purpose (speed), is it absolutely necessary for them
to be as noisy as they are, or are they just designed that way, in the same
way some morons alter their motorcycles because "loud pipes save lives"?
And, when they're idling, why do they sound (and smell) as if the engines
are only firing on half their cylinders?

Subject: Loud boats
From: "Doug Kanter"

I'm using the term "speedboats" to describe boats which sound like they have
(and probably do have) a pair of 400+ cubic inch motors in the back?
In
order to achieve their purpose (speed), is it absolutely necessary for them
to be as noisy as they are,

Not necessarily. But exhaust restrictions can lower max horse power.

or are they just designed that way, in the same
way some morons alter their motorcycles because "loud pipes save lives"?

In some cases yes. Except for the "save lives" part.

And, when they're idling, why do they sound (and smell) as if the engines
are only firing on half their cylinders?

Cam timing and lift patterns.

Capt. Bill

"LaBomba182" wrote in message
...
Subject: Loud boats
From: "Doug Kanter"

I'm using the term "speedboats" to describe boats which sound like they
have
(and probably do have) a pair of 400+ cubic inch motors in the back?
In
order to achieve their purpose (speed), is it absolutely necessary for
them
to be as noisy as they are,

Not necessarily. But exhaust restrictions can lower max horse power.

or are they just designed that way, in the same
way some morons alter their motorcycles because "loud pipes save lives"?

In some cases yes. Except for the "save lives" part.

And, when they're idling, why do they sound (and smell) as if the engines
are only firing on half their cylinders?

Cam timing and lift patterns.

Capt. Bill

Are they, in fact, misfiring at idle?

"Doug Kanter" wrote in message
...

Cam timing and lift patterns.

Capt. Bill

Are they, in fact, misfiring at idle?



An engine that is designed for high RPMs will often sacrifice low RPM (idle)
performance to get the engine to breath better at high RPMs.

At the higher RPMs the momentum (or lack thereof) is a substantial factor in
the air flow. The exhaust gases flowing out the manifold have momentum, and
can actually help scavenge the cylinder if the valves are left open a little
past "top dead center". Likewise, it takes a while to get the air intake to
start flowing, plus it takes a while to actually get the valves to open. It
is common for a high RPM cam to have both the exhaust and intake valves open
together for a short period of time.

This works well at 6000 + RPM. It doesn't work well at 800 RPM.

I wouldn't call it a "misfire" as much as the intake system is getting all
messed up.

Rod

Subject: Loud boats
From: "Rod McInnis"

"Doug Kanter" wrote in message
...

Cam timing and lift patterns.

Capt. Bill

Are they, in fact, misfiring at idle?



An engine that is designed for high RPMs will often sacrifice low RPM (idle)
performance to get the engine to breath better at high RPMs.

At the higher RPMs the momentum (or lack thereof) is a substantial factor in
the air flow. The exhaust gases flowing out the manifold have momentum, and
can actually help scavenge the cylinder if the valves are left open a little
past "top dead center". Likewise, it takes a while to get the air intake to
start flowing, plus it takes a while to actually get the valves to open. It
is common for a high RPM cam to have both the exhaust and intake valves open
together for a short period of time.

This works well at 6000 + RPM. It doesn't work well at 800 RPM.

I wouldn't call it a "misfire" as much as the intake system is getting all
messed up.

Rod

What he said. :-)

Capt. Bill

On Mon, 02 Aug 2004 15:41:54 GMT, "Doug Kanter"
wrote:
I'm using the term "speedboats" to describe boats which sound like they have
(and probably do have) a pair of 400+ cubic inch motors in the back? In
order to achieve their purpose (speed), is it absolutely necessary for them
to be as noisy as they are, or are they just designed that way, in the same
way some morons alter their motorcycles because "loud pipes save lives"?
And, when they're idling, why do they sound (and smell) as if the engines
are only firing on half their cylinders?
=====================================

It's just more thoughtless behavior from the ego challenged "look at
me" crowd. There's no reason at all why a pair of 454s has to be
louder than any other well mannered I/O except that the owners prefer
it that way. Unfortunately in their "it's a free country behavior",
they bring down a lot of unwanted attention and enforcement on the
rest of us. Much of the support for "Save the Manatee" madness
originated with waterfront property owners who were fed up with the
constant noise of jet skis and go fasts zipping up and down the
shoreline at high speed (and decibel levels).

The unique stumbling idle is from the use of high performance cam
shafts that are designed to run well only at top RPMs.

"Wayne.B" wrote in message
...
On Mon, 02 Aug 2004 15:41:54 GMT, "Doug Kanter"
wrote:
I'm using the term "speedboats" to describe boats which sound like they
have
(and probably do have) a pair of 400+ cubic inch motors in the back? In
order to achieve their purpose (speed), is it absolutely necessary for
them
to be as noisy as they are, or are they just designed that way, in the
same
way some morons alter their motorcycles because "loud pipes save lives"?
And, when they're idling, why do they sound (and smell) as if the engines
are only firing on half their cylinders?
=====================================

It's just more thoughtless behavior from the ego challenged "look at
me" crowd. There's no reason at all why a pair of 454s has to be
louder than any other well mannered I/O except that the owners prefer
it that way. Unfortunately in their "it's a free country behavior",
they bring down a lot of unwanted attention and enforcement on the
rest of us. Much of the support for "Save the Manatee" madness
originated with waterfront property owners who were fed up with the
constant noise of jet skis and go fasts zipping up and down the
shoreline at high speed (and decibel levels).

The unique stumbling idle is from the use of high performance cam
shafts that are designed to run well only at top RPMs.


Interesting, that last line. Does that explain why some of these boats smell
like unburned gasoline's blarping out of the exhausts, or is that another
issue?

Interesting, that last line. Does that explain why some of these boats smell
like unburned gasoline's blarping out of the exhausts,

That is exactly what is happening. A high performance cam will hold the intake
and exhaust valves open at the same time, longer than a normal cam. (overlap)
At high RPMs when air is flowing fast and plugs are firing 50 or 60 times a
second, that is a good thing but at lower RPMs you are actually sucking intake
mix directly into the exhaust.You can also be popping back through the carb.
You will see the same thing with race cars ...
....and 2 strokes.

"Greg" wrote in message
...
Interesting, that last line. Does that explain why some of these boats
smell
like unburned gasoline's blarping out of the exhausts,

That is exactly what is happening. A high performance cam will hold the
intake
and exhaust valves open at the same time, longer than a normal cam.
(overlap)
At high RPMs when air is flowing fast and plugs are firing 50 or 60 times
a
second, that is a good thing but at lower RPMs you are actually sucking
intake
mix directly into the exhaust.You can also be popping back through the
carb.
You will see the same thing with race cars ...
...and 2 strokes.

Great. As if the 100+ decibel noise weren't enough.....

I do agree these folks may be calling undue attention to boats. It may be just
a matter of time before we are all running air pumps and catalytic converters.