4.3 2bbl to 4.3 4bbl
 

I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

for all I know. Yes, it is a matter of intake and carb. Of course your
throttle linkage[s] may need some rerouting, but I don't think it's
that much of a chore. The manifold should bolt right on.


crystalguy wrote:
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

That's basically it. You can use an aftermarket automotive aluminum intake
buit the carb needs to be marine. For that engine I'd stick with a 600 or
650 cfm max. Any bigger would really be overcarbed. Don't expect any
overwhelming performnace leap. Maybe 3 mph or so more on the top end.

"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

The other three things that may contribute to higher horsepower are the cam,
compression ratio and valve size. You should check out those things before
you go to the trouble changing the carb.
LD
"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

I do agree, that you probably wouldn't ahve that much ore to gain, but
I suppose it depends on what you want. For pulling a ski , i would
think you could get a better hole shot, and plane out quicker. But I do
agree,t hat you probably wouldn't notice that much difference on top
end.



But even so, arn't the fron two bbls. usually smaller on a 4, and the
bigger back two usually kick in at 3/4 to WOT?


Lee henning wrote:
The other three things that may contribute to higher horsepower are the cam,
compression ratio and valve size. You should check out those things before
you go to the trouble changing the carb.
LD
"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

Depends on the 4 barrel. The quadrajet has smaller primaries than
secondaries. The holleys have 4 equal sized. The secondaries on the quadra
jet are vacuum actuated so they open as the engine demands. That will be
under higher loads but that is not some specific throttle position.
Obviously it tends to be the more open throttle positions. The holley can
be had as a vacuum or mechanical secondaries. The main reason for a bigger
carb is to deliver more air/gas at wide open throttle. The holley typically
is not the best choice for fuel economy but is preferred for perfomance.
The holley is also so common that they are easy to find parts for.

wrote in message
oups.com...
I do agree, that you probably wouldn't ahve that much ore to gain, but
I suppose it depends on what you want. For pulling a ski , i would
think you could get a better hole shot, and plane out quicker. But I do
agree,t hat you probably wouldn't notice that much difference on top
end.



But even so, arn't the fron two bbls. usually smaller on a 4, and the
bigger back two usually kick in at 3/4 to WOT?


Lee henning wrote:
The other three things that may contribute to higher horsepower are the
cam,
compression ratio and valve size. You should check out those things
before
you go to the trouble changing the carb.
LD
"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.


As everyone said should be an easy swap, do you really want to pump more gas
through the boat for a slight increase in power?

I went through the whole thought process with my 4.3. Decided against the 4
barrel due to cost/ gas/ and minor performance increase.

THEN I had water in my oil, found the 2 barrel manifold cracked. Replaced
it with a 4 barrel manifold, bought an adapter plate, rejetted my two barrel
and gained about 10-15 hp. Top end only improved very slightly, but low end
torque and hole shot are a lot better.

4.3 2bbl to 4.3 4bbl
 

and it takes 15hp to gain 1mph! What are you trying to do & why?

"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

More top end doesn't interest me.
I just bought the boat and won't be able to pull tubes behind it till
spring.
We are all about multiple tubes.....175hp may be enough for us but I
want to know what my options are if it isn't.

Lost In Space/Woodchuck wrote:
and it takes 15hp to gain 1mph! What are you trying to do & why?

"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

More top end doesn't interest me.
I just bought the boat and won't be able to pull tubes behind it till
spring.
We are all about multiple tubes.....175hp may be enough for us but I
want to know what my options are if it isn't.

Lost In Space/Woodchuck wrote:
and it takes 15hp to gain 1mph! What are you trying to do & why?

"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

A bigger carb will not particularly improve your holeshot. Make sure it is
tuned up and running properly. One thing you can do is under prop it. By
putting a smaller pitch prop on the engine will be able to rev quicker out
of the hole. It will be up to you to not over rev it while running at high
speeds though by you backing off the throttle. I would drop at least two,
may be 4 sizes. In other words if you have a 21 get a 19 or mayybe even a
17. By used on ebay or elsewhere and you can usually sell without much
loss. Keep you old prop and you can swap them back and forth depending on
what you are planning to do for the day.

"crystalguy" wrote in message
ups.com...
More top end doesn't interest me.
I just bought the boat and won't be able to pull tubes behind it till
spring.
We are all about multiple tubes.....175hp may be enough for us but I
want to know what my options are if it isn't.

Lost In Space/Woodchuck wrote:
and it takes 15hp to gain 1mph! What are you trying to do & why?

"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

James wrote:
A bigger carb will not particularly improve your holeshot. Make sure it is
tuned up and running properly. One thing you can do is under prop it. By
putting a smaller pitch prop on the engine will be able to rev quicker out
of the hole. It will be up to you to not over rev it while running at high
speeds though by you backing off the throttle. I would drop at least two,
may be 4 sizes. In other words if you have a 21 get a 19 or mayybe even a
17. By used on ebay or elsewhere and you can usually sell without much
loss. Keep you old prop and you can swap them back and forth depending on
what you are planning to do for the day.



Kind of makes me wonder why boats don't have a 2 speed gearbox, wouldn't
even have to be synchronized or capable of shifting under power, but to
be able to select speed or acceleration without swapping the prop could
really come in handy.

4.3 2bbl to 4.3 4bbl
 

"James Sweet" wrote in message
news:zYcYg.392$AR6.222@trndny02...


Kind of makes me wonder why boats don't have a 2 speed gearbox, wouldn't
even have to be synchronized or capable of shifting under power, but to be
able to select speed or acceleration without swapping the prop could
really come in handy.

This subject comes up from time to time. Automatic adjusting, variable
pitch props were marketed for a while. These guys sell parts for them, but
I haven't seen a complete unit.

http://www.land-and-sea.com/marine/t...rque-shift.htm

Eisboch

4.3 2bbl to 4.3 4bbl
 

From my hot rodding days I remember that the primary venturi size of a 4
barrel carburetor is usually smaller than the venturi size of a 2 barrel
carburetor so having a 4 barrel carb can have more good results than bad. If
given a choice fuel injections is an improvement over a carburetor(s).

I think that some here talk about being sure your motor is really tuned
properly and maybe try different propeller sizes. You can one prop that is
for high speed cruising with lighter loads and then a prop for pulling
skiers or hauling lots of people and gear. This is probably much cheaper
than changing the manifold and carburetor.

--
Bill Kiene

Kiene's Fly Shop
Sacramento, CA, USA

Web site: www.kiene.com


"crystalguy" wrote in message
oups.com...
More top end doesn't interest me.
I just bought the boat and won't be able to pull tubes behind it till
spring.
We are all about multiple tubes.....175hp may be enough for us but I
want to know what my options are if it isn't.

Lost In Space/Woodchuck wrote:
and it takes 15hp to gain 1mph! What are you trying to do & why?

"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.

4.3 2bbl to 4.3 4bbl
 

I believe there are multi-speed xmissions based on the powerglide two speed
gm automatic. Smaller boats don't have the room for them. They also add to
the price. I tried a land+sea variable pitch prop (got one used) but it
takes considerable "tweaking" to get to to work optimally for your boat.
Decided it wasn't worth the trouble. If you have enough engine the only
real issue is holeshot. Otherwise the operating range of the boat on plane
is well inside the power range of the engine. Usually you can prop it
slightly one way or another to give a little preference to which ever you
can the most about, holeshot or topend. I have a 21 and a 23 pitch props.
For watersports I use the 21 but it will let the rpms get over 5k so I have
to watch not to run it a wot for more than a minute or two.

"James Sweet" wrote in message
news:zYcYg.392$AR6.222@trndny02...
James wrote:
A bigger carb will not particularly improve your holeshot. Make sure it
is tuned up and running properly. One thing you can do is under prop it.
By putting a smaller pitch prop on the engine will be able to rev quicker
out of the hole. It will be up to you to not over rev it while running
at high speeds though by you backing off the throttle. I would drop at
least two, may be 4 sizes. In other words if you have a 21 get a 19 or
mayybe even a 17. By used on ebay or elsewhere and you can usually sell
without much loss. Keep you old prop and you can swap them back and
forth depending on what you are planning to do for the day.


Kind of makes me wonder why boats don't have a 2 speed gearbox, wouldn't
even have to be synchronized or capable of shifting under power, but to be
able to select speed or acceleration without swapping the prop could
really come in handy.

4.3 2bbl to 4.3 4bbl
 

Pulling, it's all in the prop! Reduce pitch and increase diameter and you
will pull their arms off.


"crystalguy" wrote in message
oups.com...
More top end doesn't interest me.
I just bought the boat and won't be able to pull tubes behind it till
spring.
We are all about multiple tubes.....175hp may be enough for us but I
want to know what my options are if it isn't.

Lost In Space/Woodchuck wrote:
and it takes 15hp to gain 1mph! What are you trying to do & why?

"crystalguy" wrote in message
oups.com...
I recently purchased a 1988 Sea Ray with a Mercruiser V-6 4.3 with a 2
barrel carb (175 hp)
Is it possible to convert this to a 4.3 with 4 barrel carb (205hp)
Is it just a matter of changing the carb and intake or are the
ingnitions different?

Any input would be greatly appreciated.