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.

"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.


Sounds like running lean. Check the float adjustment.

You pooched the power valve installation or the float level is too low.
JR
JamesE wrote:
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.



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Home Page: http://www.seanet.com/~jasonrnorth

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.

I'd go back to the original needle even though the spring one should work.
It may be it changes how you should adjust the float. A low float could
cause this. There is nothing else to do for the power valve. Did a new
power valve come with the kit? If it did then I'd try the old one just to
see if that changes anything. Also does the carb have a small filter at the
inlet? If so check that as well for being in in the correct direction.

"JamesE" wrote in message
ups.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.

Check the fuel filter and pump. Make sure it's actually getting the right
flow.

On Sep 7, 11:47 am, "Bill Kearney" wkearney-99@hot-mail-com wrote:
Check the fuel filter and pump. Make sure it's actually getting the right
flow.

The main fuel filter and pump would cause a drop in rpms after the
engine got up to speed if they were a problem. The fuel in the float
bowl should be enough to get to wot initially without a bog unless
delivery to the carb was seriously reduced and then it would not run
any distance even at less than full throttle. His description sounds
like it will run around at 3/4 throttle for a long time.

On Sep 7, 7:28 am, JamesE wrote:
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.

One other thought I had is did you make sure that full throttle at the
controls is really opening the carb plates all the way?

Also check your accellerator pump for proper adjustment and function.

Does it always bog no matter how slowly you advance the throttle? If
it bogs even when opening the throttle slowly that does suggest a main
jet issue.

jamesgangnc wrote:
did you make sure that full throttle at the
controls is really opening the carb plates all the way?

A linkage adjustment issue? Yep, that's the first thing that popped
into my head when he said "not a serious bog, more like advancing the
throttle isn't making any difference".

Rick

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