JamesE wrote in news:1189164531.137067.326800@
19g2000hsx.googlegroups.com:

I must have checked the float level 10 times before I put it back
together. Of course I could be measuring it wrong however. On my
rebuild kit it had a note that said that with four cylinder engines
experiencing rough idle and flooding that it may be necessary to
change to a spring loaded needle. So I changed it from the original
solid needle to the spring needle and then readjusted the float
level. Could this be causing the problem? Also you mentioned that I
could have put in the power valve wrong. What could have gone wrong
with it? I just put the gasket on and screwed it in. Was there
something else I should have done? Thanks, James.


Silly me, but have we checked our fuel pumping capacity? It may simply
be running out of fuel! Fuel pump, fuel filters, clogged lines,
restrictions, clogged tank vent?

Open the tank's inlet at WOT and see if it doesn't speed up...clogged
vent.
Temporarily install an outboard motor primer bulb at the inlet of the
fuel pump for testing. Does it collapse when the throttle is opened?
(vacuum on fuel line). If you pump it by hand when the engine bogs, does
the engine perk up and have more power? (bad fuel pump). With the engine
off, if you pump the bulb, does it pump a few times, then get impossible
to pump (float valve closing off)...or does it continue to pump? (fuel
pump diaphram has a hole in it). Great little piece of test equipment,
primer bulbs. Too bad it's not "legal" to leave them in the line all the
time on inboards.

Let's test the fuel supply before we tear the carb all apart for the 22nd
time, ok?

Larry
--
Search youtube for "Depleted Uranium"
The ultimate dirty bomb......

Let's read the original post before we make a bunch of off suggestions, ok?

"Larry" wrote in message
...
JamesE wrote in news:1189164531.137067.326800@
19g2000hsx.googlegroups.com:

I must have checked the float level 10 times before I put it back
together. Of course I could be measuring it wrong however. On my
rebuild kit it had a note that said that with four cylinder engines
experiencing rough idle and flooding that it may be necessary to
change to a spring loaded needle. So I changed it from the original
solid needle to the spring needle and then readjusted the float
level. Could this be causing the problem? Also you mentioned that I
could have put in the power valve wrong. What could have gone wrong
with it? I just put the gasket on and screwed it in. Was there
something else I should have done? Thanks, James.


Silly me, but have we checked our fuel pumping capacity? It may simply
be running out of fuel! Fuel pump, fuel filters, clogged lines,
restrictions, clogged tank vent?

Open the tank's inlet at WOT and see if it doesn't speed up...clogged
vent.
Temporarily install an outboard motor primer bulb at the inlet of the
fuel pump for testing. Does it collapse when the throttle is opened?
(vacuum on fuel line). If you pump it by hand when the engine bogs, does
the engine perk up and have more power? (bad fuel pump). With the engine
off, if you pump the bulb, does it pump a few times, then get impossible
to pump (float valve closing off)...or does it continue to pump? (fuel
pump diaphram has a hole in it). Great little piece of test equipment,
primer bulbs. Too bad it's not "legal" to leave them in the line all the
time on inboards.

Let's test the fuel supply before we tear the carb all apart for the 22nd
time, ok?

Larry
--
Search youtube for "Depleted Uranium"
The ultimate dirty bomb......

The adjustments are all related to idle and low speed operation. Doesn't
have anything to do with high speed operation.

"john" wrote in message
...

"JamesE" wrote in message
oups.com...
I just rebuilt the carburetor on my 3.0 liter mercruiser because the
engine was running rough. Well I rebuilt it very meticulously because
this was my first time rebuilding it and I thought everything went
well. Now the engine is running smoother and not flooding but the
problem is that after 3/4 throttle the carburetor starts to bog. It
runs great up until 3/4 throttle but after that it starts to bog, not
a serious bog, more like advancing the throttle isn't making any
difference. Well this wouldn't bother me because I never go that fast
anyway but since it is only a 4 cylinder I need that power to get on
plane with people in the boat as the boat is really struggling right
now. So if anyone has any ideas on what would cause this I would
appreciate it. I am assuming it is the carburetor because I didn't
have this problem until I rebuilt it. Thanks.


OK everything else has been mentioned - try adjusting the air mixture
screw on the front of the carb. Start it up and let it idle, watch your
tach and turn for max RPM then turn it in 1/4 (or leave it).

The correct way to check for the throttle plates opening fully is to move
the throttle to the full throttle position with the engine off then open the
choke plate by hand and look down the throat of the carb to see that the
throtle plates are completely open.

When you say misfiring do you mean that a cylinder misses it firing cycle?
Or it is back firing?

Maybe the float setting is totally pooched. With a correctly functioning
carb the common reason an engine will blow gas back out of the carb is a
stuck valve. Totally out of wack timing or the wires on the wrong cylinders
can also cause it to, but with a 4 banger if you don't have all 4 cylinders
mostly producing power you really notice it. Can you tell if the excess gas
is coming out of the float bowl overflow? That's the vent tube that look
like a J and the open end points back into the carb venturi.

Usually if you and the written instructions are not in agreement then most
likely problem is you are doing something wrong. Start there before you
assume the instructions are wrong.

You did nothing else to this engine at all? It was running rough before you
decided to rebuild the carb? How did you diagnose that the carb needed
rebuilding?


"JamesE" wrote in message
ups.com...
Thanks for the replies. Regarding the statement about the plates not
getting to full throttle, it is definitely getting to full throttle
and the more I advance the throttle the worse the bog gets until it
starts to misfire around full throttle. Also I have already tried
adjusting the mixture screw many times but that isn't helping. I
don't think it is a fuel delivery issue because it is getting plenty
of fuel. I think it is probably getting too much fuel. The other day
I was driving with the engine cover off and the flame arrestor off and
then I had someone go full throttle. The gas was spraying out in
droplets and just spraying all over the place. I don't think that
this is right, so what would cause this? And no matter how fast or
slow I advance the throttle it seems to always bog in the same place.
Also the bog happens all the time, I can't run for any length of time
above 3/4 throttle. Also on the instruction sheet for the rebuilding
kit it gave me the measurement for the accelerator pump but when I
adjusted it like that a piece of the linkage would hit and prevent the
throttle from opening all the way to the throttle stop. So I kind of
just did it by feel and guessed where it should be because that didn't
seem right. So if anyone has any suggestions on why it would be
getting to much gas I would appreciate it. Since this was my first
rebuild I wasn't really expecting it to work, I just wanted to give it
a shot and gain experience. But since I am no expert at carburetors I
think I am going to have it professionally rebuilt that way I can get
some use out of it before the end of the summer. Thanks for the
help. James

On Sep 10, 9:45 am, "john" wrote:
"jamesgangnc" wrote in message

...

The adjustments are all related to idle and low speed operation. Doesn't
have anything to do with high speed operation.

BUT, my 4.3 would choke and bog when I slammed the throttle wide open.
Adjusting the mixture screw fixed that. It did not seem to do anything to
my full throttle.

A bog coming off idle could be a bad idle mixture. But that's not the
problem this guy has. The mixture screw you are talking about is the
idle mixture. It adjusts the fuel flow through the idle circuit in
the carb. When the plates are in the idle position there is not
enough air flow though the carb to draw gas from the main jets. The
idle circuit suppliments the gas supply at idle to maintain the right
mixture.

Thanks for all the suggestions guys. What I ended up doing was having
it professionally rebuilt. I wanted to get the most out of what is
left of the boating season. Also when I rebuilt the carburetor I did
my best to adjust everything according to the directions. So I
figured that if I tried to readjust the float according to the
directions I would just end up right where I started. So I decided
that I wasn't quite qualified yet. But now the problem is gone. Also
just so you know I asked what was wrong with it and they said that
they had to readjust the float. So you guys were right. James

On Sat, 15 Sep 2007 20:43:18 -0700, JamesE
wrote:

Thanks for all the suggestions guys. What I ended up doing was having
it professionally rebuilt. I wanted to get the most out of what is
left of the boating season. Also when I rebuilt the carburetor I did
my best to adjust everything according to the directions. So I
figured that if I tried to readjust the float according to the
directions I would just end up right where I started. So I decided
that I wasn't quite qualified yet. But now the problem is gone. Also
just so you know I asked what was wrong with it and they said that
they had to readjust the float. So you guys were right. James

Sometimes that's the best approach. I had no problem rebuilding
engines, but wouldn't touch a carb after I saw I was batting .500.
Nice to hear you're back in business.

--Vic