Greetings,

How do you adjust the idle speed on a Merc 40HP, 2 cylinder, 2-stroke?
I adjusted the cable via the barrel nut, but it made no difference in
the idle speed...

There's a threaded rod above the linkage, but I don't want to fiddle
with anything unless I'm sure. This is my first outboard in 30 years
of boating!!

Thanks!

I would advise you get a manual before you turn the wrong thing and screw
your timing up.

--
Bill
Chesapeake, Va


wrote in message
...
Greetings,

How do you adjust the idle speed on a Merc 40HP, 2 cylinder, 2-stroke?
I adjusted the cable via the barrel nut, but it made no difference in
the idle speed...

There's a threaded rod above the linkage, but I don't want to fiddle
with anything unless I'm sure. This is my first outboard in 30 years
of boating!!

Thanks!

wrote:
Greetings,

How do you adjust the idle speed on a Merc 40HP, 2 cylinder, 2-stroke?
I adjusted the cable via the barrel nut, but it made no difference in
the idle speed...

There's a threaded rod above the linkage, but I don't want to fiddle
with anything unless I'm sure. This is my first outboard in 30 years
of boating!!

Thanks!

Generally, there are 2 screwdriver adjusted mixture adjustments on a
carburettor body. One (the larger) is the full power mixture
adjustment, the smaller one is the idle mixture adjustment. In
addition there is a minimum throttle stop adjustment on the
butterfly (throttle) shaft rest / stop, which adjusts the minimum
opening of the throttle at idle. Adjusting that will control the at
idle throttle butterfly position and idle speed. The power
adjustment is made under load at maximum power, adjusted for maximum
power.

The throttle stop and idle mixture adjustments interact, especially
if the throttle stop is adjusted outside it's normal range, which
can cause the idle jet to be "left out" of the narrow throttle
opening gap at idle. This can cause a wonky opening stumble at low
power setting changes.

You can sense this by closing the throttle stop all the way then
opening it slowly. You should see that if too "closed" at idle, a
double sequence of increases in idle speed will result, or there
will be a decrease in speed while "opening" the adjustment while it
is still too closed. (in other words, while the butterfly is beyond
the minimum opening position and opening again on the inside of the
intake tube) Do not try to use the first increase position, ie,
from too closed, opening, idle may slow down, then speed up, then
slow down, then speeds up normally. Use the position between where
it slows down and then speeds up again as your idle position,
adjusting the speed as required. Adjust while engine is hot, no
choke, and in conjunction with the best idle speed adjusted by the
idle mixture adjustment. Do not be tempted to set the idle super
slow in neutral, it will stall during warmup in gear. If the
butterfly's idle position is wrong, the idle mixture adjustment may
have little or no effect. This may be incorrectly interpereted as
being a clogged idle jet.

After a long lay up, you will probably need to clean the carb
insides before it will work right. The jets may be dirty, plugged
up, or the inlet float needle and seat may not seal properly,
leading to flooding or starvation. Gummy carbs are the "most
popular" engine problems in the spring.

The cable adjustment is usually intended to take out slack in the
cable and adjust it's installation, not intended to control anything
on the carb. You should not use it to adjust the idle.

You may be better off to take it to a qualified mechanic. Being
stranded in the middle of the lake is seldom enjoyable.

Good luck!

Terry K

On Thu, 05 Aug 2004 21:51:17 GMT, Terry Spragg
wrote:


You may be better off to take it to a qualified mechanic. Being
stranded in the middle of the lake is seldom enjoyable.

Good luck!

Terry K

Thanks for the detailed response.......Sounds a little more
complicated than setting the idle on my 350 inboards!!

I think I'll let someone that knows what their doing give it a once
over. It idles quite roughly, and too high, so there's likely more
than one adjustment that needs to be made.....