I have a 40 Merc outboard, 4 cyl, twin carbs. At what approximate rpm do I
set the jets? Been a while since I looked at them, are there two, or just
one? It is somewhat difficult to set the high end, as you are bouncing
along and trying to listen and turn the screwdriver all at once. Which carb
do I set first? Or does one carb feed two cylinders, and it doesn't matter,
and I just need to get them both close? Do I do it strictly by sound, or do
I get them right, then screw them in and count the turns, then back them
both back out to the same turns on both?

Thanks

Steve

On Feb 10, 12:12*pm, "Steve B" wrote:
I have a 40 Merc outboard, 4 cyl, twin carbs. *At what approximate rpm do I
set the jets? *Been a while since I looked at them, are there two, or just
one? *It is somewhat difficult to set the high end, as you are bouncing
along and trying to listen and turn the screwdriver all at once. *Which carb
do I set first? *Or does one carb feed two cylinders, and it doesn't matter,
and I just need to get them both close? *Do I do it strictly by sound, or do
I get them right, then screw them in and count the turns, then back them
both back out to the same turns on both?

Thanks

Steve

Don't know what motor you have but usually the high speed jets are
fixed. i.e. you need to swap jets to adjust them. I suspect you are
adjusting the idle jets. If it's a dual bore carb there will be two
idle screws. The manual would tell you how many turns out they should
be set. You can tweak them with the motor in gear in the water, at
idle speed, to try to lean out the mixture some for less smoke or plug
fouling but at the risk of leaning it out too much and wrecking your
motor. Unless your fouling plugs or have an exceptionally rich idle
I'd stick with the factory setting.

On 2/10/10 12:23 PM, stp wrote:
On Feb 10, 12:12 pm, "Steve wrote:
I have a 40 Merc outboard, 4 cyl, twin carbs. At what approximate rpm do I
set the jets? Been a while since I looked at them, are there two, or just
one? It is somewhat difficult to set the high end, as you are bouncing
along and trying to listen and turn the screwdriver all at once. Which carb
do I set first? Or does one carb feed two cylinders, and it doesn't matter,
and I just need to get them both close? Do I do it strictly by sound, or do
I get them right, then screw them in and count the turns, then back them
both back out to the same turns on both?

Thanks

Steve

Don't know what motor you have but usually the high speed jets are
fixed. i.e. you need to swap jets to adjust them. I suspect you are
adjusting the idle jets. If it's a dual bore carb there will be two
idle screws. The manual would tell you how many turns out they should
be set. You can tweak them with the motor in gear in the water, at
idle speed, to try to lean out the mixture some for less smoke or plug
fouling but at the risk of leaning it out too much and wrecking your
motor. Unless your fouling plugs or have an exceptionally rich idle
I'd stick with the factory setting.


"The manual would tell you..."

Assuming one has a manual...

:)

"stp" wrote in message
...
On Feb 10, 12:12 pm, "Steve B" wrote:
I have a 40 Merc outboard, 4 cyl, twin carbs. At what approximate rpm do I
set the jets? Been a while since I looked at them, are there two, or just
one? It is somewhat difficult to set the high end, as you are bouncing
along and trying to listen and turn the screwdriver all at once. Which
carb
do I set first? Or does one carb feed two cylinders, and it doesn't
matter,
and I just need to get them both close? Do I do it strictly by sound, or
do
I get them right, then screw them in and count the turns, then back them
both back out to the same turns on both?

Thanks

Steve

Don't know what motor you have but usually the high speed jets are
fixed. i.e. you need to swap jets to adjust them. I suspect you are
adjusting the idle jets. If it's a dual bore carb there will be two
idle screws. The manual would tell you how many turns out they should
be set. You can tweak them with the motor in gear in the water, at
idle speed, to try to lean out the mixture some for less smoke or plug
fouling but at the risk of leaning it out too much and wrecking your
motor. Unless your fouling plugs or have an exceptionally rich idle
I'd stick with the factory setting.

reply: Yeah, I know it is a good idea to buy a manual, but they are from
$25 to $100, and everyone has a different idea on which one to get. I think
I'll be getting a good Mercury one soon, if I can get one at a decent price
on ebay.

Anyone know what the factory settings are? From my experiences with motors,
1 1/2 out from shut is a starting point.

A friend of mine's dad (he's probably 75) has a lot of experience with
outboards in the past. I'll get him over to look at it, for this and other
reasons. Just wanted to understand this for myself.

Class?

Class?

Steve

On Feb 10, 1:41*pm, "Steve B" wrote:
"stp" wrote in message

...
On Feb 10, 12:12 pm, "Steve B" wrote:

I have a 40 Merc outboard, 4 cyl, twin carbs. At what approximate rpm do I
set the jets? Been a while since I looked at them, are there two, or just
one? It is somewhat difficult to set the high end, as you are bouncing
along and trying to listen and turn the screwdriver all at once. Which
carb
do I set first? Or does one carb feed two cylinders, and it doesn't
matter,
and I just need to get them both close? Do I do it strictly by sound, or
do
I get them right, then screw them in and count the turns, then back them
both back out to the same turns on both?

Thanks

Steve

Don't know what motor you have but usually the high speed jets are
fixed. i.e. you need to swap jets to adjust them. I suspect you are
adjusting the idle jets. If it's a dual bore carb there will be two
idle screws. The manual would tell you how many turns out they should
be set. You can tweak them with the motor in gear in the water, at
idle speed, to try to lean out the mixture some for less smoke or plug
fouling but at the risk of leaning it out too much and wrecking your
motor. Unless your fouling plugs or have an exceptionally rich idle
I'd stick with the factory setting.

reply: *Yeah, I know it is a good idea to buy a manual, but they are from
$25 to $100, and everyone has a different idea on which one to get. *I think
I'll be getting a good Mercury one soon, if I can get one at a decent price
on ebay.

Anyone know what the factory settings are? *From my experiences with motors,
1 1/2 out from shut is a starting point.

A friend of mine's dad (he's probably 75) has a lot of experience with
outboards in the past. *I'll get him over to look at it, for this and other
reasons. *Just wanted to understand this for myself.

Class?

Class?

Steve

What model year is your motor?

If I were doing this without a manual myself I would start at 1-1/2
turns then turn each screw 1/4 turn out and repeat until the motor
start to get real blubbery, note the number of turns out, then turn
each screw in 1/4 turn at a time. The motor should speed up as it
leans out and then start to run rough when you get too lean. Note the
turns. Your adjustment is somewhere in the middle. I'd try 1/2 turn
out from full lean. If the motor hesitates when you gun the throttle
then you are too lean. Try another 1/8 turn out. You can tell a lot by
idling for 5-10 minutes and reading the plugs.

"stp" wrote in message
...
On Feb 10, 1:41 pm, "Steve B" wrote:
"stp" wrote in message

...
On Feb 10, 12:12 pm, "Steve B" wrote:

I have a 40 Merc outboard, 4 cyl, twin carbs. At what approximate rpm do
I
set the jets? Been a while since I looked at them, are there two, or
just
one? It is somewhat difficult to set the high end, as you are bouncing
along and trying to listen and turn the screwdriver all at once. Which
carb
do I set first? Or does one carb feed two cylinders, and it doesn't
matter,
and I just need to get them both close? Do I do it strictly by sound, or
do
I get them right, then screw them in and count the turns, then back them
both back out to the same turns on both?

Thanks

Steve

Don't know what motor you have but usually the high speed jets are
fixed. i.e. you need to swap jets to adjust them. I suspect you are
adjusting the idle jets. If it's a dual bore carb there will be two
idle screws. The manual would tell you how many turns out they should
be set. You can tweak them with the motor in gear in the water, at
idle speed, to try to lean out the mixture some for less smoke or plug
fouling but at the risk of leaning it out too much and wrecking your
motor. Unless your fouling plugs or have an exceptionally rich idle
I'd stick with the factory setting.

reply: Yeah, I know it is a good idea to buy a manual, but they are from
$25 to $100, and everyone has a different idea on which one to get. I
think
I'll be getting a good Mercury one soon, if I can get one at a decent
price
on ebay.

Anyone know what the factory settings are? From my experiences with
motors,
1 1/2 out from shut is a starting point.

A friend of mine's dad (he's probably 75) has a lot of experience with
outboards in the past. I'll get him over to look at it, for this and other
reasons. Just wanted to understand this for myself.

Class?

Class?

Steve

What model year is your motor?

If I were doing this without a manual myself I would start at 1-1/2
turns then turn each screw 1/4 turn out and repeat until the motor
start to get real blubbery, note the number of turns out, then turn
each screw in 1/4 turn at a time. The motor should speed up as it
leans out and then start to run rough when you get too lean. Note the
turns. Your adjustment is somewhere in the middle. I'd try 1/2 turn
out from full lean. If the motor hesitates when you gun the throttle
then you are too lean. Try another 1/8 turn out. You can tell a lot by
idling for 5-10 minutes and reading the plugs.

reply: Going fishing this weekend. Sounds like something I can do at the
lake. It is an '89. Do I keep it at low idle, or push the fast idle handle
forward any?

Steve

Steve

On Feb 10, 11:21*pm, "Steve B" wrote:
"stp" wrote in message

...
On Feb 10, 1:41 pm, "Steve B" wrote:





"stp" wrote in message

....
On Feb 10, 12:12 pm, "Steve B" wrote:

I have a 40 Merc outboard, 4 cyl, twin carbs. At what approximate rpm do
I
set the jets? Been a while since I looked at them, are there two, or
just
one? It is somewhat difficult to set the high end, as you are bouncing
along and trying to listen and turn the screwdriver all at once. Which
carb
do I set first? Or does one carb feed two cylinders, and it doesn't
matter,
and I just need to get them both close? Do I do it strictly by sound, or
do
I get them right, then screw them in and count the turns, then back them
both back out to the same turns on both?

Thanks

Steve

Don't know what motor you have but usually the high speed jets are
fixed. i.e. you need to swap jets to adjust them. I suspect you are
adjusting the idle jets. If it's a dual bore carb there will be two
idle screws. The manual would tell you how many turns out they should
be set. You can tweak them with the motor in gear in the water, at
idle speed, to try to lean out the mixture some for less smoke or plug
fouling but at the risk of leaning it out too much and wrecking your
motor. Unless your fouling plugs or have an exceptionally rich idle
I'd stick with the factory setting.

reply: Yeah, I know it is a good idea to buy a manual, but they are from
$25 to $100, and everyone has a different idea on which one to get. I
think
I'll be getting a good Mercury one soon, if I can get one at a decent
price
on ebay.

Anyone know what the factory settings are? From my experiences with
motors,
1 1/2 out from shut is a starting point.

A friend of mine's dad (he's probably 75) has a lot of experience with
outboards in the past. I'll get him over to look at it, for this and other
reasons. Just wanted to understand this for myself.

Class?

Class?

Steve

What model year is your motor?

If I were doing this without a manual myself I would start at 1-1/2
turns then turn each screw 1/4 turn out and repeat until the motor
start to get real blubbery, note the number of turns out, then turn
each screw in 1/4 turn at a time. The motor should speed up as it
leans out and then start to run rough when you get too lean. Note the
turns. Your adjustment is somewhere in the middle. I'd try 1/2 turn
out from full lean. If the motor hesitates when you gun the throttle
then you are too lean. Try another 1/8 turn out. You can tell a lot by
idling for 5-10 minutes and reading the plugs.

reply: *Going fishing this weekend. *Sounds like something I can do at the
lake. *It is an '89. *Do I keep it at low idle, or push the fast idle handle
forward any?

Steve

Steve- Hide quoted text -

- Show quoted text -

If you have a control box with the idle handle then all that is doing
is bumping your idle stop screw up a notch. So, no. Engine warm, in
the water, in gear..

On 2/10/10 1:41 PM, Steve B wrote:
wrote in message
...
On Feb 10, 12:12 pm, "Steve wrote:
I have a 40 Merc outboard, 4 cyl, twin carbs. At what approximate rpm do I
set the jets? Been a while since I looked at them, are there two, or just
one? It is somewhat difficult to set the high end, as you are bouncing
along and trying to listen and turn the screwdriver all at once. Which
carb
do I set first? Or does one carb feed two cylinders, and it doesn't
matter,
and I just need to get them both close? Do I do it strictly by sound, or
do
I get them right, then screw them in and count the turns, then back them
both back out to the same turns on both?

Thanks

Steve

Don't know what motor you have but usually the high speed jets are
fixed. i.e. you need to swap jets to adjust them. I suspect you are
adjusting the idle jets. If it's a dual bore carb there will be two
idle screws. The manual would tell you how many turns out they should
be set. You can tweak them with the motor in gear in the water, at
idle speed, to try to lean out the mixture some for less smoke or plug
fouling but at the risk of leaning it out too much and wrecking your
motor. Unless your fouling plugs or have an exceptionally rich idle
I'd stick with the factory setting.

reply: Yeah, I know it is a good idea to buy a manual, but they are from
$25 to $100, and everyone has a different idea on which one to get. I think
I'll be getting a good Mercury one soon, if I can get one at a decent price
on ebay.

Anyone know what the factory settings are? From my experiences with motors,
1 1/2 out from shut is a starting point.

A friend of mine's dad (he's probably 75) has a lot of experience with
outboards in the past. I'll get him over to look at it, for this and other
reasons. Just wanted to understand this for myself.

Class?

Class?

Steve



You know, there have been any number of Merc 40's over the years, and
there have been substantial changes in the spec's of these outboards
from time to time. Your search for information might be easier if you
posted/looked using the serial number of your outboard.

You could always call a Merc dealer and ask...Most dealers will handle
reasonable questions, especially if they think you are going to be a
parts customers. The parts business is profitable.