Mercruiser Carb Conversion
 

wrote in message
...
Phantman wrote:
I've always wondered why the designers
didn't just get the cooling water through the bottom of the boat
like
any normal straight inboard setup.

Jim wrote:
I suspect that the engineers felt it
unnecessary to reinvent a proven design

JamesGangNC wrote:
The inside water pumps are basically the same design rubber vaned
pumps. All of them will self prime if needed and the distance is not
far.

Jim wrote:
I don't think the internal pumps are self priming. I would consider
changing
my mind on that if I could see some proof.

Phantman wrote:
Are you familiar with inboards? I don't mean sterndrives. I mean
proven design straight inboards that have been around since long
before sterndrives were dreamed up (and still common everywhere). They
get their raw water through the boat's bottom via a thru hull fitting.
Whether or not they use a standard automotive pump or a special marine
design that's self priming, I'm not sure. But whatever it is, it sure
looks like a standard auto water pump and bolts right into place.

Jim wrote:
Rick, the pump under discussion is the raw water pump that brings water
into
the boat, not the circulating pump.

Well, lets get on the same page then. My question was, "why wouldn't
the designer of a sterndrive use the same less complex method of
cooling water intake that Inboards have always used (and still use).
It's a time tested and proven design, no hauling the boat for impeller
maintenance, and less expensive to build. I see no advantage to their
more complex, more difficult to maintain design. That's not to say it
doesn't work at all, obviously it does. But it's one of several
complexities of standard sterndrive design that could easily be
simplified imho.

Rick
Who knows why they designed the IO the way they did. I don't know if it's
more complex. The main difference is the IO makes 2 90 degree power train
turns vs the outboards 1 turn.
Cheaper to build, maybe? Less work and expense for the boat builder(no
bronze thru hull, screen, hoses, sea strainer, etc.)

How would you simplify the design of the IO?

Mercruiser Carb Conversion
 

Phantman wrote:
I've always wondered why the designers
didn't just get the cooling water through the bottom of the boat
like
any normal straight inboard setup.

Jim wrote:
I suspect that the engineers felt it
unnecessary to reinvent a proven design

JamesGangNC wrote:
The inside water pumps are basically the same design rubber vaned
pumps. All of them will self prime if needed and the distance is not
far.

Jim wrote:
I don't think the internal pumps are self priming. I would consider
changing
my mind on that if I could see some proof.

Phantman wrote:
Are you familiar with inboards? I don't mean sterndrives. I mean
proven design straight inboards that have been around since long
before sterndrives were dreamed up (and still common everywhere). They
get their raw water through the boat's bottom via a thru hull fitting.
Whether or not they use a standard automotive pump or a special marine
design that's self priming, I'm not sure. But whatever it is, it sure
looks like a standard auto water pump and bolts right into place.

Jim wrote:
Rick, the pump under discussion is the raw water pump that brings water
into the boat, not the circulating pump.

Phantman wrote:
Well, lets get on the same page then. My question was, "why wouldn't
the designer of a sterndrive use the same less complex method of
cooling water intake that Inboards have always used (and still use).
It's a time tested and proven design, no hauling the boat for impeller
maintenance, and less expensive to build. I see no advantage to their
more complex, more difficult to maintain design. That's not to say it
doesn't work at all, obviously it does. But it's one of several
complexities of standard sterndrive design that could easily be
simplified imho.

Jim wrote:
Who knows why they designed the IO the way they did. I don't know if it's
more complex. The main difference is the IO makes 2 90 degree power train
turns vs the outboards 1 turn.
Cheaper to build, maybe? Less work and expense for the boat builder(no
bronze thru hull, screen, hoses, sea strainer, etc.)
How would you simplify the design of the IO?

Most importantly, I would eliminate the boots. All of them. Which
means I would have to start over from scratch with a design. This
forum probably isn't the place to get into that. But eliminating the
outboard impeller and transom intake system would be a step in the
right direction as far as I can tell. I've asked this same question
of mechanics, engineers and some fairly knowledgable people, but so
far I haven't found anyone that can explain why the outboard impeller
is a better idea. I'm sure I'm not the only one who's thought about it
though, including whoever designed the I/O in the first place. I wish
I knew what he was thinkin'.

Rick

Mercruiser Carb Conversion
 

wrote in message
...
Phantman wrote:
I've always wondered why the designers
didn't just get the cooling water through the bottom of the boat
like
any normal straight inboard setup.

Jim wrote:
I suspect that the engineers felt it
unnecessary to reinvent a proven design

JamesGangNC wrote:
The inside water pumps are basically the same design rubber vaned
pumps. All of them will self prime if needed and the distance is not
far.

Jim wrote:
I don't think the internal pumps are self priming. I would consider
changing
my mind on that if I could see some proof.

Phantman wrote:
Are you familiar with inboards? I don't mean sterndrives. I mean
proven design straight inboards that have been around since long
before sterndrives were dreamed up (and still common everywhere). They
get their raw water through the boat's bottom via a thru hull fitting.
Whether or not they use a standard automotive pump or a special marine
design that's self priming, I'm not sure. But whatever it is, it sure
looks like a standard auto water pump and bolts right into place.

Jim wrote:
Rick, the pump under discussion is the raw water pump that brings water
into the boat, not the circulating pump.

Phantman wrote:
Well, lets get on the same page then. My question was, "why wouldn't
the designer of a sterndrive use the same less complex method of
cooling water intake that Inboards have always used (and still use).
It's a time tested and proven design, no hauling the boat for impeller
maintenance, and less expensive to build. I see no advantage to their
more complex, more difficult to maintain design. That's not to say it
doesn't work at all, obviously it does. But it's one of several
complexities of standard sterndrive design that could easily be
simplified imho.

Jim wrote:
Who knows why they designed the IO the way they did. I don't know if it's
more complex. The main difference is the IO makes 2 90 degree power train
turns vs the outboards 1 turn.
Cheaper to build, maybe? Less work and expense for the boat builder(no
bronze thru hull, screen, hoses, sea strainer, etc.)
How would you simplify the design of the IO?

Most importantly, I would eliminate the boots. All of them. Which
means I would have to start over from scratch with a design. This
forum probably isn't the place to get into that. But eliminating the
outboard impeller and transom intake system would be a step in the
right direction as far as I can tell. I've asked this same question
of mechanics, engineers and some fairly knowledgable people, but so
far I haven't found anyone that can explain why the outboard impeller
is a better idea. I'm sure I'm not the only one who's thought about it
though, including whoever designed the I/O in the first place. I wish
I knew what he was thinkin'.

Rick
Staright inboards also have a raw water pump. It is just mounted on the
engine block and driven by a belt like the other accessories. I think you
are confused about how inboard engine boat cooling systems work.

All of them have a pump that supplies water from the outside. It is a
rubber vaned. In merc alphas it's on the outboard leg. On the rest it's
usually mounted on the front lower side of the engine. The impeller needs
to be replaced from time to time because if wear. They also have the
conventional automotive type recirculating water pump mounted on the upper
front of the engine.

The thermostat is more complicated on a boat. Rather than simply blocking
the water it switches the paths. When the engine is cold the thermostat
allows water in but causes it to continually circulate inside the block.
That circulation is done by the original automotive pump that is mounted on
the front of the engine. The rest of the water supplied by the raw water
pump is diverted to the exhaust system. When the engine is hot the water
from the raw water pump goes into the engine and then goes to the exhaust.
That way no matter what the position of the thermostat new water is always
going to the exhaust.

The original design is because the early i/os really did use the lower half
of an outboard. Early big merc outboards actually have some parts that are
interchangeable with the early i/o legs. As to the reason, it let them
build a boat with some of the advantages of an outboards but without the
finicky, easily damaged, aluminum 2 stroke engines. Instead they used
cheaper existing automotive cast iron blocks. The automotive block is
engineered with a lot of excess strength. It can stand more abuse or lack
of care than an aluminum 2 stroke. Outboard engines run a lot closer to
many of the theoretical limits of the engine. That lets them have a much
better hp/weight ratio. But it also means that mistakes and problems don't
have to push them far before they break. Outboards are much better for
trailering and the ability to trim the prop position and use the prop for
steering are advantages over straight inboards. Those are the features that
they were trying to leverage with i/os.

Mercruiser Carb Conversion
 

jamesgangnc wrote:


The original design is because the early i/os really did use the lower half
of an outboard. Early big merc outboards actually have some parts that are
interchangeable with the early i/o legs. As to the reason, it let them
build a boat with some of the advantages of an outboards but without the
finicky, easily damaged, aluminum 2 stroke engines.

I/O's came about mainly because auto engine makers provided cheap
engines that could be mated, sort of, with a lower unit assembly that
delivered higher horsepower at a lower price than the outboards of the day.

Mercruiser Carb Conversion
 

"HK" wrote in message
. ..
jamesgangnc wrote:


The original design is because the early i/os really did use the lower
half of an outboard. Early big merc outboards actually have some parts
that are interchangeable with the early i/o legs. As to the reason, it
let them build a boat with some of the advantages of an outboards but
without the finicky, easily damaged, aluminum 2 stroke engines.

I/O's came about mainly because auto engine makers provided cheap engines
that could be mated, sort of, with a lower unit assembly that delivered
higher horsepower at a lower price than the outboards of the day.

And they still are one of the most popular consumer boat configurations sold
today.

Mercruiser Carb Conversion
 

"jamesgangnc" wrote:
I think you
are confused about how inboard engine boat cooling systems work.

No, I'm not confused. I've owned and maintained a number of inboards.
Moreso than I/Os. Both gasoline and diesel. I'm apparently just not
communicating my thoughts very well.

All of them have a pump that supplies water from the outside.

And you can maintain them without hauling the boat in half the time
and half the effort of an I/O.

On the rest it's
usually mounted on the front lower side of the engine.

Good idea. No impeller in the leg at all? All of mine had an impeller
in the lower outdrive except one with it on the top.

As to the reason, it let them
build a boat with some of the advantages of an outboards but without the
finicky, easily damaged, aluminum 2 stroke engines.

And with a lot more power to push much larger boats. Outboards didn't
have nearly the HP back then as they have now. I think the basic idea
for the I/O was valid and sound. I just don't think the designers put
enough thought outside their box. They could have built a much less
complex and more maintenace free system. One with something more than
rubber boots between it and sinking. But they didn't and the market
responded by demanding huge outboards. Which it now has.
I'm not saying I/Os are a bad idea. I'm saying they could have been
less complex which usually means better.

Rick

Mercruiser Carb Conversion
 

jamesgangnc wrote:
"HK" wrote in message
. ..
jamesgangnc wrote:

The original design is because the early i/os really did use the lower
half of an outboard. Early big merc outboards actually have some parts
that are interchangeable with the early i/o legs. As to the reason, it
let them build a boat with some of the advantages of an outboards but
without the finicky, easily damaged, aluminum 2 stroke engines.
I/O's came about mainly because auto engine makers provided cheap engines
that could be mated, sort of, with a lower unit assembly that delivered
higher horsepower at a lower price than the outboards of the day.

And they still are one of the most popular consumer boat configurations sold
today.




Yawn. McDonalds probably still sells the most burgers...doesn't mean
they are any good.

Mercruiser Carb Conversion
 

On Apr 24, 9:22*am, wrote:
"jamesgangnc" wrote:
I think you
are confused about how inboard engine boat cooling systems work.

No, I'm not confused. I've owned and maintained a number of inboards.
Moreso than I/Os. Both gasoline and diesel. *I'm apparently just not
communicating my thoughts very well.

All of them have a pump that supplies water from the outside.

And you can maintain them without hauling the boat in half the time
and half the effort of an I/O.

On the rest it's
usually mounted on the front lower side of the engine.

Good idea. No impeller in the leg at all? All of mine had an impeller
in the lower outdrive except one with it on the top.

As to the reason, it let them
build a boat with some of the advantages of an outboards but without the
finicky, easily damaged, aluminum 2 stroke engines.

And with a lot more power to push much larger boats. Outboards didn't
have nearly the HP back then as they have now. I think the basic idea
for the I/O was valid and sound. I just don't think the designers put
enough thought outside their box. They could have built a much less
complex and more maintenace free system. One with something more than
rubber boots between it and sinking. But they didn't and the market
responded by demanding huge outboards. Which it now has.
I'm not saying I/Os are a bad idea. I'm saying they could have been
less complex which usually means better.

Rick

Your earlier post "Whether or not they use a standard automotive pump
or a special marine design that's self priming, I'm not sure." lead me
to think you didn't understand. Because they all use both pumps. The
difference between the alphas and the bravo/volvo/trs/etc drives is
that the alphas continue to use the raw water pump in the leg while
the others used a belt driven raw water pump on the engine.

And you'll get no arguement out of me that the raw water pump in the
engine compartment is way better and much easier to service. I was
only discussing how it got where it is. The orginal merc drive went
through several minor design improvements to give us the 2nd
generation alpha we have today. And engineering wise it is still not
even close to state of the art. But it works and has proven to be a
pretty reliable platform. Volume made it extremely cheap at the bulk
level. That kept it around. Merc as well as others have designed
much better outdrives. They simply cost more and many consumers don't
appreciate the difference therefore consumers don't want to pay the
difference. That volume is changing and more modern i/os are a bigger
part of the market now.

I'm not saying the i/o is "better" that the other two propulsion
solutions. All 3 have their pros and cons. How those factor in also
depends on the application. In some situations the i/o pros make it
attractive.

And there really isn't a real higher risk of sinking because the i/o
has a rubber boot coupling the drive to the exterior prop assembly.
The i/o is far more likely to survive a high speed hard strike to the
drive train without compromising the hull integrity that a
conventional inboard. The i/o absorbes most of the force in the gear
train and typically destroys props, gears, and couplings. The i/o
physical unit is typically kicked up rather than sheared off the
transom. On a conventional inboard usually the prop shaft is ripped
out or severely bent and there is frequently compromise to the rear
lower hull or stuffing box. Of course the outboard installation will
also kick up and often can stand anything up to and including being
ripped clean off the back without compromising hull integrity.

I don't think the hp difference was all that great, merc had some
pretty big inline 4s and 6s early in the outboard game. While they
did not match the hp of the early small block v8 engines if you factor
in the weight difference they were pretty powerful engines. Inboards
with automotive engines already predated i/os. So the larger boats
did not need i/os. Outboards simply don't attract a significant part
of the consumer base. Never have. It's all about what sells first
and engineering is always second to that. That's not unique to boats,
that is true in everything.

Mercruiser Carb Conversion
 

JamesGangNC wrote:
And there really isn't a real higher risk of sinking because the i/o
has a rubber boot coupling the drive to the exterior prop assembly.

I'd get rid of that one too lol!

On a conventional inboard usually the prop shaft is ripped
out or severely bent and there is frequently compromise to the rear
lower hull or stuffing box.

An unprotected prop is like playing Russian Roulette where I live with
sandbars, oyster reefs, shallow water etc. A keel under the prop
means everything, and I mean all the way to the rudder. You don't see
that often with trailerable boats. Shamrock is one exception but I
don't think their keel protects the rudder either. I'd have to go
looksee. A Tunnel is another way to go. But the least fuel efficient
boat I've ever owned was a Penn Yann Tunnel Drive. It was great for
bumping along on shallow sandy bottoms but the prop was small and Gawd
that sucker drank fuel.

I don't think the hp difference was all that great, merc had some
pretty big inline 4s and 6s early in the outboard game.

My first I/O was a 225hp OMC in a 1971 23' Seabird. Back then, nobody
built an outboard transom into boats that size. I think the largest
outboard you could buy was maybe 125-130hp and even on a smaller boat,
it would drink twice the fuel of a 225hp I/O. I used to pass outboard
boats everywhere I went. Waaaay later on, after O/Bs became more
powerful, guys began repowering boats like mine by bolting an O/B
bracket onto them. I eventually sold my Seabird as is but a friend of
mine still has one just like it that he repowered. He claims the
improvement in speed and handling is like night and day. Not to
mention the weight loss for trailering.

Inboards
with automotive engines already predated i/os. So the larger boats
did not need i/os.

They did if they were trailerable and liked the kick up advantages of
an outboard. And we're talking about a different era here. Back then,
a 23', 5200 lb boat was considered a BIG trailerable boat.

Rick

Mercruiser Carb Conversion
 

On Apr 24, 11:56*am, wrote:
JamesGangNC wrote:
And there really isn't a real higher risk of sinking because the i/o
has a rubber boot coupling the drive to the exterior prop assembly.

I'd get rid of that one too lol!

On a conventional inboard usually the prop shaft is ripped
out or severely bent and there is frequently compromise to the rear
lower hull or stuffing box.

An unprotected prop is like playing Russian Roulette where I live with
sandbars, oyster reefs, shallow water etc. *A keel under the prop
means everything, and I mean all the way to the rudder. You don't see
that often with trailerable boats. Shamrock is one exception but I
don't think their keel protects the rudder either. I'd have to go
looksee. A Tunnel is another way to go. But the least fuel efficient
boat I've ever owned was a Penn Yann Tunnel Drive. It was great for
bumping along on shallow sandy bottoms but the prop was small and Gawd
that sucker drank fuel.

I don't think the hp difference was all that great, merc had some
pretty big inline 4s and 6s early in the outboard game.

My first I/O was a 225hp OMC in a 1971 23' Seabird. Back then, nobody
built an outboard transom into boats that size. I think the largest
outboard you could buy was maybe 125-130hp and even on a smaller boat,
it would drink twice the fuel of a 225hp I/O. *I used to pass outboard
boats everywhere I went. *Waaaay later on, after O/Bs became more
powerful, guys began repowering boats like mine by bolting an O/B
bracket onto them. I eventually sold my Seabird as is but a friend of
mine still has one just like it that he repowered. He claims the
improvement in speed and handling is like night and day. Not to
mention the weight loss for trailering.

Inboards
with automotive engines already predated i/os. *So the larger boats
did not need i/os.

They did if they were trailerable and liked the kick up advantages of
an outboard. And we're talking about a different era here. Back then,
a 23', 5200 lb *boat was considered a BIG trailerable boat.

Rick

That's why you're not designing boat propousion systems. Pay close
attention. Boats with i/o drives are not sinking because of a failure
inthe rubber boot onthe coupling.