"bomar" wrote in message
...
Buy, borrow, or steal the book "Small Block Chevy Marine Performance" by
the
GOD of GM marine engines Dennis Moore.
Read it cover to cover and it will answer all your questions.
Amazon, eBay, or www.mooreperformance.org
Dennis has forgotten more than anyone else will ever know about GM based
marine engines.


Dennis is an excellent STOCK Mercruiser mechanic. PERIOD. He is 10 years
behind the times whenit comes to anything high performance.

"no one" wrote in message ...
I called summit, they didn't stock anything called vortec...

Vortec is a word GM used to describe a swirling of the intake gasses in the
cylinder and combustion chamber - what specifically are you talking about?

"Dave" wrote in message
snip

Just in case you are still interested, these heads are on the Summit
website under:

Engines & components/Cylinder heads and accessories/ GM Performance
Vortec Heads

$259 each with valve and springs.


I'll agree with the others it will take a LOT more power to increase
speed 10mph. A buddy of mine wanted his stock 454 powered 24ft Baja to
go faster. Basically he had to double the power to increase top speed
by 12mph.

"David McNally" wrote in message
om...
I'll agree with the others it will take a LOT more power to increase
speed 10mph. A buddy of mine wanted his stock 454 powered 24ft Baja to
go faster. Basically he had to double the power to increase top speed
by 12mph.

You have got it. PLUS onthat Baja, it can be trimmed out of the water.
An inboard can't. Its taking me 200+ more HP to gain 12-15 mph on my
Formula.

"lifespeed" wrote in message
om...
"no one" wrote in message
...
Now I got a lot of flak a couple months ago about using O2 sensors in
marine
applications ( a statement was made that O2 sensors are only valuable
for
emissions and catalyst health - which I personally do not agree with but
am
not in a position to argue)

Comments on closed loop aftermarket MPFI marine applications???

You can do aftermarket SEFI, closed loop with O2 and other cool things
too. Costs money and effort, but it does work, and work well.

What do you mean by "work well"? Is it as good as open loop or measurably
better? Are there noticeable gains in power, torque, startability,
driveability, fuel economy, and/or smoothness? I still maintain that
feedback fuel control exists only to keep a catalyst operating at peak
efficiency. Even closed loop systems go to open loop enriched conditions
under max power situations and/or for the sake of smoothness. I can see
that maybe a closed loop system might be slightly better on gas but if it's
not controlled well then you're playing with fire. Otherwise I think you're
adding complexity for minimal gain. If someone wants to experiment. by all
means go for it - that someone just won't be me.

Geoff, show me the evidence O2 sensors are primarily for cat performance.
If you've ever seen a fi system go into a bad full rich open loop state,
you'll see the cat is REAL efficient. Like white hot efficient.


"Geoff" wrote in message
gy.com...

"lifespeed" wrote in message
om...
"no one" wrote in message
...
Now I got a lot of flak a couple months ago about using O2 sensors in
marine
applications ( a statement was made that O2 sensors are only valuable
for
emissions and catalyst health - which I personally do not agree with
but
am
not in a position to argue)

Comments on closed loop aftermarket MPFI marine applications???

You can do aftermarket SEFI, closed loop with O2 and other cool things
too. Costs money and effort, but it does work, and work well.

What do you mean by "work well"? Is it as good as open loop or measurably
better? Are there noticeable gains in power, torque, startability,
driveability, fuel economy, and/or smoothness? I still maintain that
feedback fuel control exists only to keep a catalyst operating at peak
efficiency. Even closed loop systems go to open loop enriched conditions
under max power situations and/or for the sake of smoothness. I can see
that maybe a closed loop system might be slightly better on gas but if
it's
not controlled well then you're playing with fire. Otherwise I think
you're
adding complexity for minimal gain. If someone wants to experiment. by
all
means go for it - that someone just won't be me.

"Geoff" wrote in message igy.com...
You can do aftermarket SEFI, closed loop with O2 and other cool things
too. Costs money and effort, but it does work, and work well.

What do you mean by "work well"? Is it as good as open loop or measurably
better? Are there noticeable gains in power, torque, startability,
driveability, fuel economy, and/or smoothness? I still maintain that
feedback fuel control exists only to keep a catalyst operating at peak
efficiency. Even closed loop systems go to open loop enriched conditions
under max power situations and/or for the sake of smoothness. I can see
that maybe a closed loop system might be slightly better on gas but if it's
not controlled well then you're playing with fire. Otherwise I think you're
adding complexity for minimal gain. If someone wants to experiment. by all
means go for it - that someone just won't be me.

By work well, I mean improved fuel economy at part throttle for the
ordinary O2 sensors. They don't have a wide enough range to cover
higher throttle settings. It is worth doing. I have such a setup on
a powerful 454 Chevy and the idle quality and fuel economy are very
good considering the high output.

The wideband O2 sensors can go a step further and keep the mixture
"tuned" at WOT also. Haven't tried this yet, but I probably will in
the future. More expensive, I'm waiting for prices to drop.

Yes, you can map your engine open-loop. Obviously, my engine is
mapped open-loop for heavy loads. If you are a knowledgeable engine
tuner you can do a good job. However, it is hard to account for
varying temperatures and air pressures perfectly. Open-loop is
certainly good enough, but it is hard to produce the
perfect-under-all-conditions power and economy that a wideband O2 will
provide.

Lifespeed

"Tom Ruta" wrote in message
...

You are crazy to think that adding 10 mph to the top end is (a) wise
or (b) economical. these are semi-displacement hulls and the vast
majority will be squirrely above 50. Maybe with some trim tabs.
Look at Malibu's Corvette for instance.

I don't think what you call "semi-displacement" hulls are any more dangerous
than other hulls at a given speed.

I've been 82 mph in a blown Malibu, and it was quite stable...in fact, it
felt very secure.

The real issue with hot-rodding a inboard ski boat is the practallity of it.
With the prop fixed facing downward, it will always "push up" the rear of
the boat, resulting in the front going down, resulting in a higher wetted
surface.

This is exactly what high-performance boaters try to minimize...wetted
surface. Maybe that's why my buddies Malibu seemed so "solid"...it had a
good plant in the water, however, that engine would easily break 100 in a
"trimable" hull.

--
It's just about going fast...that's all...

http://home.insight.rr.com/cgreen/

"no one" wrote in message ...
Geoff, show me the evidence O2 sensors are primarily for cat performance.

Here is a training document from Toyota. Read the first line of the
document #37- "oxygen and air/ fuel sensors"

http://smccd.net/accounts/sullivank/

If you've ever seen a fi system go into a bad full rich open loop state,
you'll see the cat is REAL efficient. Like white hot efficient.

The problem is with three way converters. Read document #64 from the
same link it will explain the need for tight fuel control on catalytic
converter equipped engines.

Hope this helps.




"Geoff" wrote in message
gy.com...

"lifespeed" wrote in message
om...
"no one" wrote in message
...
Now I got a lot of flak a couple months ago about using O2 sensors in
marine
applications ( a statement was made that O2 sensors are only valuable
for
emissions and catalyst health - which I personally do not agree with
but
am
not in a position to argue)

Comments on closed loop aftermarket MPFI marine applications???

You can do aftermarket SEFI, closed loop with O2 and other cool things
too. Costs money and effort, but it does work, and work well.

What do you mean by "work well"? Is it as good as open loop or measurably
better? Are there noticeable gains in power, torque, startability,
driveability, fuel economy, and/or smoothness? I still maintain that
feedback fuel control exists only to keep a catalyst operating at peak
efficiency. Even closed loop systems go to open loop enriched conditions
under max power situations and/or for the sake of smoothness. I can see
that maybe a closed loop system might be slightly better on gas but if
it's
not controlled well then you're playing with fire. Otherwise I think
you're
adding complexity for minimal gain. If someone wants to experiment. by
all
means go for it - that someone just won't be me.

"NetSock" wrote in message ...
I don't think what you call "semi-displacement" hulls are any more dangerous
than other hulls at a given speed.

It might take more than one ride to verify this . . .

I've been 82 mph in a blown Malibu, and it was quite stable...in fact, it
felt very secure.

A nose-down attitude has more implications than just drag. Dynamic
balance and re-entering the water after hitting some chop come to
mind.

Lifespeed

On Fri, 30 Jan 2004 08:02:41 -0500, "NetSock"
wrote:

....
I don't think what you call "semi-displacement" hulls are any more dangerous
than other hulls at a given speed.


Compared to what? A supercharged jon boat? Put me in a V at 60+
please.

I've been 82 mph in a blown Malibu, and it was quite stable...in fact, it
felt very secure.


I'd love to see GPS proof of that.

...
This is exactly what high-performance boaters try to minimize...wetted
surface. Maybe that's why my buddies Malibu seemed so "solid"...it had a
good plant in the water, however, that engine would easily break 100 in a
"trimable" hull.


He should have added a set of Bennett tabs.