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