This is in response to a thread that was discussing the limits of
naturally aspirated HP in a 305 c.i.d. engine.

Well, first, I must confess I don't know too much about recreational
boating engines specifically. However, there is much in common between
car and boat engines. As far as reliable operation is concerned, lets
look a moment (bear with me) at the Infiniti G35 VQ 3.5 liter 6
cylinder engine. Normally aspirated, it puts out 300 HP (up from 260).
And it has been rated one of the top engines in a car under 50K for
about 10 years. Now I realize it isn't apples to apples. The air
intake might be more restricted in the boat engine without a fair about
of help--I don't know. But the point is today's engines are more
advanced, without the bolt-on technology enhancements.

Just to get a sense of what's possible by comparison, the Nissan
Skyline GT-R 2.6 liter inline 6 cylinder (RB26DETT) with twin turbos
has been modified over and over again to 600HP+ with just bolt-ons and
a new engine management computer as a start. Some have modified them
to greater than 1000HP. That's not naturally aspirated, but that's
also a 2.6 - 2.8 liter engine at over 1000HP without NOS! Incredible.

Look at the Suzuki Hayabusa. 1.3 liter inline 4 cylinder motorcycle
engine running about 170 HP stock. Mods take it over 200 easy, still
naturally aspirated. And turbo Busa's run upwards of 400HP+ without
NOS--certainly pricier.

Now, there are design limitations to some engines, but the naturally
aspirated 305 is capable of more than 260 HP. Using that engine block
with modern components and design tweaks, it would seem that much more
can be achieved. If not, use a different engine. Unfortunately, I
don't have specific 305 examples on the top of my mind, and I'm not
sure what some might call reliable performance either.

However, take this additional example from the 2007 SALEEN S281 3V
Coupe Mustang, which is a high quality built engine by Saleen. Running
it moderately most of the time and hot sometimes with proper
maintenance, this thing wouldn't quit on you for a couple decades or
so...

ENGINE
Type 4.6L, 3V, SOHC V-8
Bore and Stroke 3.55 x 3.54 in.
Displacement 4.6 liters, 281 cu in.
Accessory Pulleys Saleen Underdrive Pulleys
Exhaust System Saleen Stainless, 2.5 in. Variable Exhaust
Horsepower 335 bhp @ 5200 RPM
Torque 345 lb-ft @ 4500 RPM
Fuel Premium Unleaded 91 Octane
Intake Saleen Design Hi-Flow Inlet Tube and Air Box

Granted, Saleen's Hi-Flow Inlet Tube helps air intake, and a front
engine design puts the intake in position to swallow a lot of air, but
this is still the naturally aspirated version of this engine, which is
smaller than the 305 by 24 cubic inches. And one thing I don't see
limitations on in a boat engine is exhaust. It seems that should be an
advantage from a design potential standpoint. Not sure what emissions
regs there are, but I would be surprised if it is more than cars in the
state of California. Haven't heard any push for hybrid boat engines
for example.

By the way, this upfit mustang costs around 44K retail, which includes
ALL of Saleen's adders. The engine itself, without the highly touted
Saleen Supercharger, isn't that particularly expensive, which means it
isn't simply a case of throwing money at overengineering like a Porche
or Ferrari or something. It is powerful, practical, naturally
aspirated and reliable--which are all criteria of this topic. And I'm
not saying boats need this engine. I'm saying the same concept can be
applied to many engines.

Of course, this is a high volume engine (in its original configuration
from Ford) which helps the base price of each. A specialty engine
would have to cost more to deliver the same result when looking at
amortization differences (total cost & profit / num of builds).

usafhg wrote:
This is in response to a thread that was discussing the limits of
naturally aspirated HP in a 305 c.i.d. engine.

Well, first, I must confess I don't know too much about recreational
boating engines specifically. However, there is much in common between
car and boat engines. As far as reliable operation is concerned, lets
look a moment (bear with me) at the Infiniti G35 VQ 3.5 liter 6
cylinder engine.

At what RPM? Where is peak torque?

........


Now, there are design limitations to some engines, but the naturally
aspirated 305 is capable of more than 260 HP. Using that engine block
with modern components and design tweaks, it would seem that much more
can be achieved. If not, use a different engine. Unfortunately, I
don't have specific 305 examples on the top of my mind, and I'm not
sure what some might call reliable performance either.

However, take this additional example from the 2007 SALEEN S281 3V
Coupe Mustang, which is a high quality built engine by Saleen. Running
it moderately most of the time and hot sometimes with proper
maintenance, this thing wouldn't quit on you for a couple decades or
so...

ENGINE
Type 4.6L, 3V, SOHC V-8
Bore and Stroke 3.55 x 3.54 in.
Displacement 4.6 liters, 281 cu in.
Accessory Pulleys Saleen Underdrive Pulleys
Exhaust System Saleen Stainless, 2.5 in. Variable Exhaust
Horsepower 335 bhp @ 5200 RPM
Torque 345 lb-ft @ 4500 RPM
Fuel Premium Unleaded 91 Octane
Intake Saleen Design Hi-Flow Inlet Tube and Air Box

OK... now show us where/when the Saleen Mustang will be run for extended
periods at much more than 10-15% of it's rated peak?

Now how about that lowly 305? Your 305 will deliver 200-225 hp for
hours on end and not even whimper. Try that with the Saleen.


Rob

Of course, this is a high volume engine (in its original configuration
from Ford) which helps the base price of each. A specialty engine
would have to cost more to deliver the same result when looking at
amortization differences (total cost & profit / num of builds).




Boat engines often run at max power constantly- you throttle up and leave
it. Those high-performance auto engines are built to go 'balls out' for a
short period of time. It's doubtful that any "marinized" version of some of
the newer, lighter engines would handle the constant stresses that would be
thrown at them.

Granted, boat builders could do a better job of squeezing more HP out of
"lower end" marine engines, but then again, that's how they can charge so
much for the "upgrades" to more powerful ones.

usafhg wrote:
This is in response to a thread that was discussing the limits of
naturally aspirated HP in a 305 c.i.d. engine.

Well, first, I must confess I don't know too much about recreational
boating engines specifically. However, there is much in common between
car and boat engines. As far as reliable operation is concerned, lets
look a moment (bear with me) at the Infiniti G35 VQ 3.5 liter 6
cylinder engine. Normally aspirated, it puts out 300 HP (up from 260).
And it has been rated one of the top engines in a car under 50K for
about 10 years. Now I realize it isn't apples to apples. The air
intake might be more restricted in the boat engine without a fair about
of help--I don't know. But the point is today's engines are more
advanced, without the bolt-on technology enhancements.




Marine and aircraft engines operate in a completely different
environment than automotive engines. They often run at or near full
throttle for hours on end and if the motor breaks down at sea or up in
the air you can't simply pull over. For this reason the motors tend to
be derated somewhat from what the blocks are actually capable of producing.

There are a number of other issues in boat engines. The most important one
is that they have to run at a significant percentage of rated horsepower for
a lot longer durations that car engines. It is perfectly normal for a boat
engine to have to run at 60-70% of rated power for possibly hours. That's
like running your infiniti at 110 mph for hours. While it probably will do
it, doing it every day will have an effect on the life of the engine. When
these auto engines are used for racing which also involves this sort of
stress they are often rebuilt or replaced after every race. That's not
practical in a consumer boat.

"usafhg" wrote in message
ups.com...
This is in response to a thread that was discussing the limits of
naturally aspirated HP in a 305 c.i.d. engine.

Well, first, I must confess I don't know too much about recreational
boating engines specifically. However, there is much in common between
car and boat engines. As far as reliable operation is concerned, lets
look a moment (bear with me) at the Infiniti G35 VQ 3.5 liter 6
cylinder engine. Normally aspirated, it puts out 300 HP (up from 260).
And it has been rated one of the top engines in a car under 50K for
about 10 years. Now I realize it isn't apples to apples. The air
intake might be more restricted in the boat engine without a fair about
of help--I don't know. But the point is today's engines are more
advanced, without the bolt-on technology enhancements.

Just to get a sense of what's possible by comparison, the Nissan
Skyline GT-R 2.6 liter inline 6 cylinder (RB26DETT) with twin turbos
has been modified over and over again to 600HP+ with just bolt-ons and
a new engine management computer as a start. Some have modified them
to greater than 1000HP. That's not naturally aspirated, but that's
also a 2.6 - 2.8 liter engine at over 1000HP without NOS! Incredible.

Look at the Suzuki Hayabusa. 1.3 liter inline 4 cylinder motorcycle
engine running about 170 HP stock. Mods take it over 200 easy, still
naturally aspirated. And turbo Busa's run upwards of 400HP+ without
NOS--certainly pricier.

Now, there are design limitations to some engines, but the naturally
aspirated 305 is capable of more than 260 HP. Using that engine block
with modern components and design tweaks, it would seem that much more
can be achieved. If not, use a different engine. Unfortunately, I
don't have specific 305 examples on the top of my mind, and I'm not
sure what some might call reliable performance either.

However, take this additional example from the 2007 SALEEN S281 3V
Coupe Mustang, which is a high quality built engine by Saleen. Running
it moderately most of the time and hot sometimes with proper
maintenance, this thing wouldn't quit on you for a couple decades or
so...

ENGINE
Type 4.6L, 3V, SOHC V-8
Bore and Stroke 3.55 x 3.54 in.
Displacement 4.6 liters, 281 cu in.
Accessory Pulleys Saleen Underdrive Pulleys
Exhaust System Saleen Stainless, 2.5 in. Variable Exhaust
Horsepower 335 bhp @ 5200 RPM
Torque 345 lb-ft @ 4500 RPM
Fuel Premium Unleaded 91 Octane
Intake Saleen Design Hi-Flow Inlet Tube and Air Box

Granted, Saleen's Hi-Flow Inlet Tube helps air intake, and a front
engine design puts the intake in position to swallow a lot of air, but
this is still the naturally aspirated version of this engine, which is
smaller than the 305 by 24 cubic inches. And one thing I don't see
limitations on in a boat engine is exhaust. It seems that should be an
advantage from a design potential standpoint. Not sure what emissions
regs there are, but I would be surprised if it is more than cars in the
state of California. Haven't heard any push for hybrid boat engines
for example.

By the way, this upfit mustang costs around 44K retail, which includes
ALL of Saleen's adders. The engine itself, without the highly touted
Saleen Supercharger, isn't that particularly expensive, which means it
isn't simply a case of throwing money at overengineering like a Porche
or Ferrari or something. It is powerful, practical, naturally
aspirated and reliable--which are all criteria of this topic. And I'm
not saying boats need this engine. I'm saying the same concept can be
applied to many engines.

Of course, this is a high volume engine (in its original configuration
from Ford) which helps the base price of each. A specialty engine
would have to cost more to deliver the same result when looking at
amortization differences (total cost & profit / num of builds).

Well, I appreciate the responses. I am familiar with aircraft engines
a little, and certainly they are regulated much more than a car engine,
and yes they do run hot constantly (although the throttle is backed off
a little once at altitude--at least in a Cessna 340).

Perhaps that is a better analogy. And I thought about that, but I
guess I wasn't putting planes and boats in the same category. Boats
don't have as much of a problem pulling over per se as planes do. But
I suppose getting stranded would be bad, possibly very dangerous at sea
for a variety of reasons. So, that makes sense. I'd like to reiterate
my ignorance about marine engines at this point.

I just noticed someone saying you can't get much more than X amount of
power from a 305, and I'm thinking hey, that's not so. Perhaps the
better statement is that it wouldn't be the best idea to stress the
engine more than that from a money, maintenance and downtime
standpoint. But, I also see some 300-400 hour boats for sale that are
5-10 years old, and I'm thinking hey, how many miles is that at 110
mph? Upwards of 44K. The G35 won't go a couple hundred thousand miles
running that hot, but it might reliably go over 40K miles at 110 mph if
most of that is fairly constant. But I get the point. I wouldn't want
to do that to the engine even if the roads allowed. And perhaps boat
engines are supposed to run much much longer than that without an
overhaul.

And if it does relate to aircraft, a lot money is involved. Of course,
they do have RAM engine upgrade options for prop plane engines. Hey,
go turbine! Well, OK that's not practical either.

I did notice that there is a marine engine built by Suzuki that is 4.0
liters and puts out 300HP. It is built for marine applicaitons,
although I don't know it's reliability. Interesting though.

As far as HP and torque curves are concerned, I don't recall. I could
research it, but nah.

That is a good point as well. In a typical boat the power curve has to
deliver at a lower rpm. Otherwise the boat is a dog out of the hole.
Becasue as he points out boats are "one-speed" drive trains. A lot of
car engines make hp with rpm and the opportunity to do that is more
limited in a boat. That can be solved with a transmission but that
adds to the cost.

A number of the later model gm v8's in cars are able to run higher
compressions because they reversed the cooling flow. Sending the
cooler water to the heads first lowers the risk of detonation. But
that can only be done in a boat with a closed cooling system. Again
raising the cost.

Boat engines have mostly relied on more displacement to get more hp.
It's cheaper and more reliable that pushing the limits of smaller
displacement engines to get more power. As boats get larger the
percentage of the boat weight that is engine weight is less than a car
so the extra weight in a larger displacement engine is not as much of
an issue either. Also unlike cars the engine weight is not as much of
a consideration in handling. A 25 ft boat with a gm tall block (502)
will operate pretty much identically to a 25 ft boat with a 305.
Except the tall block version will be a lot faster. So why push the
305? Once you add the performance enhancements it will end up costing
as much as the tall block anyway. Over the long haul the vanilla tall
block will last much long than the souped up 305.

Short Wave Sportfishing wrote:
On 2 Oct 2006 13:55:17 -0700, "usafhg"
wrote:

Well, first, I must confess I don't know too much about recreational
boating engines specifically. However, there is much in common between
car and boat engines.

I've been watching this thread and found it very interesting.

However, I think I've got to chime in here.

In a general sense, yes, there is a commonality between car and
inboard marine engines.

Specifically, they are two different animals entirely.

I can't remember who, but somebody made the point that marine engines
are designed to run full bore all the time which is a high stress
load. High performance car engines (retail, not race) are not
designed to handle the same stresses for long periods.

The main reason is gearing. Marine engines are generally direct drive
through a drive train with no external transfer of energy by changing
gear ratios. Automotive engines don't develop their horsepower in the
same power band as marine engines and use different ratio gears to
provide mechanical advantage.

I'm sure one can take the 305 and bump the power - we've done it here
at the house with my oldest son's '92 Camaro RS audio/visual
masterpiece show car - it's not hard to bump the horsepower.

It's how the horsepower is applied that makes the different. It's
more a question of now that I have the horsepower, what the hell do I
do with it with marine engines.

In the case of a boat, you are dealing with a prop rather than a drive
train with variable or changeable gearing. Applying the power is an
entirely different set of challenges.

usafhg wrote:
This is in response to a thread that was discussing the limits of
naturally aspirated HP in a 305 c.i.d. engine.

Well, first, I must confess I don't know too much about recreational
boating engines specifically. However, there is much in common between
car and boat engines. As far as reliable operation is concerned, lets
look a moment (bear with me) at the Infiniti G35 VQ 3.5 liter 6
cylinder engine. Normally aspirated, it puts out 300 HP (up from 260).
And it has been rated one of the top engines in a car under 50K for
about 10 years. Now I realize it isn't apples to apples. The air
intake might be more restricted in the boat engine without a fair about
of help--I don't know. But the point is today's engines are more
advanced, without the bolt-on technology enhancements.

Just to get a sense of what's possible by comparison, the Nissan
Skyline GT-R 2.6 liter inline 6 cylinder (RB26DETT) with twin turbos
has been modified over and over again to 600HP+ with just bolt-ons and
a new engine management computer as a start. Some have modified them
to greater than 1000HP. That's not naturally aspirated, but that's
also a 2.6 - 2.8 liter engine at over 1000HP without NOS! Incredible.

Look at the Suzuki Hayabusa. 1.3 liter inline 4 cylinder motorcycle
engine running about 170 HP stock. Mods take it over 200 easy, still
naturally aspirated. And turbo Busa's run upwards of 400HP+ without
NOS--certainly pricier.

Now, there are design limitations to some engines, but the naturally
aspirated 305 is capable of more than 260 HP. Using that engine block
with modern components and design tweaks, it would seem that much more
can be achieved. If not, use a different engine. Unfortunately, I
don't have specific 305 examples on the top of my mind, and I'm not
sure what some might call reliable performance either.

However, take this additional example from the 2007 SALEEN S281 3V
Coupe Mustang, which is a high quality built engine by Saleen. Running
it moderately most of the time and hot sometimes with proper
maintenance, this thing wouldn't quit on you for a couple decades or
so...

ENGINE
Type 4.6L, 3V, SOHC V-8
Bore and Stroke 3.55 x 3.54 in.
Displacement 4.6 liters, 281 cu in.
Accessory Pulleys Saleen Underdrive Pulleys
Exhaust System Saleen Stainless, 2.5 in. Variable Exhaust
Horsepower 335 bhp @ 5200 RPM
Torque 345 lb-ft @ 4500 RPM
Fuel Premium Unleaded 91 Octane
Intake Saleen Design Hi-Flow Inlet Tube and Air Box

Granted, Saleen's Hi-Flow Inlet Tube helps air intake, and a front
engine design puts the intake in position to swallow a lot of air, but
this is still the naturally aspirated version of this engine, which is
smaller than the 305 by 24 cubic inches. And one thing I don't see
limitations on in a boat engine is exhaust. It seems that should be an
advantage from a design potential standpoint. Not sure what emissions
regs there are, but I would be surprised if it is more than cars in the
state of California. Haven't heard any push for hybrid boat engines
for example.

By the way, this upfit mustang costs around 44K retail, which includes
ALL of Saleen's adders. The engine itself, without the highly touted
Saleen Supercharger, isn't that particularly expensive, which means it
isn't simply a case of throwing money at overengineering like a Porche
or Ferrari or something. It is powerful, practical, naturally
aspirated and reliable--which are all criteria of this topic. And I'm
not saying boats need this engine. I'm saying the same concept can be
applied to many engines.

Of course, this is a high volume engine (in its original configuration
from Ford) which helps the base price of each. A specialty engine
would have to cost more to deliver the same result when looking at
amortization differences (total cost & profit / num of builds).

First you need to know a few things about new vs old engines and boat
engines. Most boat gas engines are based on older designs for a few
reasons. First, older automotive engines are long stroke engines, they
produced good power over their RPM range, especially at low RPM's, but
they have a limited range of RPM's. Most new automotive engines are
short stroke engines, they produce limited amounts of low end power,
they produce most of their power higher up in the RPM range, they also
rev much higher. Now on a boat, you need low end power, to get up on
plane, a short stroke engine just doesn't do that very well, they tend
to have very short lives as a result. Older engines tend to be made of
Iron, newer automotive engines are made of aluminum. Overheating on
boats is all too common because marine cooling systems are easily
clogged or restricted. Overheat an iron block engine and, as long as
you don't let it go too far, you'll probably get away with simply
clearing the blockage and going on your way. Overheat an aluminum block
engine, even minor overheating, can seriously damage the engine,
aluminum tends to warp when overheated, their just not as forgiving. I
have little doubt that your Infinity engine would have a brief, and
troubled, life, in this application. Most of the other engines you
spoke about have very limited lives even in automotive applications.
It's one of the reasons you see mostly older American designed iron
blocks being used every where in marine gas applications. The only non
American made block I know of that is common is the four cylinder
Volvo, and I beleave it's iron and a long stroke engine. Several years
ago BMW entered the stern drive market, they lasted about one season,
and you would be very hard pressed to find one still running.

the long stroke vs short. the low range power. size and weight and
handling not being a big factor like in a car. cooling system issues.
iron block vs aluminum. all these and more are great points. And it
is very true that these HP's in cars are often at high RPM's. Peak
RPM's being lower and gaining 260 HP is good, and changes a lot of my
perspective by itself. Overheating issues make a difference as well.

The thing I found most intriguing and hadn't thought of was the weight
factor of an engine to obtain larger displacement isn't an issue as you
go larger on boats.