Mercruiser 4.3 lx WOT

dozerII · May 23, 2013

Re: Mercruiser 4.3 lx WOT

Plugs are an Autolite 144, I will have to get a vacuum/ pressure gauge and follow the testing procedure listed in the sticky for the fuel system.

dozerII · Jun 10, 2013

Re: Mercruiser 4.3 lx WOT

Okay a little update. Two weeks ago I ordered a carb for the 4.3, arrived today. The boat has sat for almost three weeks since the last test hop., I took off the old carb and found not a drop of fuel in it, which doesn't make any sense to me, What do you guys think about this find??

Bondo · Jun 10, 2013

Re: Mercruiser 4.3 lx WOT

dozerII said:
Okay a little update. Two weeks ago I ordered a carb for the 4.3, arrived today. The boat has sat for almost three weeks since the last test hop., I took off the old carb and found not a drop of fuel in it, which doesn't make any sense to me, What do you guys think about this find??

Ayuh,... Leaked through into the intake,...

achris · Jun 10, 2013

Re: Mercruiser 4.3 lx WOT

Those Weber 4 bbl carbs are known to dribble after shut-off. That why it's dry.... Known problem that Merc won't acknowledge....again!

dozerII · Jun 10, 2013

Re: Mercruiser 4.3 lx WOT

Bond-o said:
Ayuh,... Leaked through into the intake,...

From where?

achris said:
Those Weber 4 bbl carbs are known to dribble after shut-off. That why it's dry.... Known problem that Merc won't acknowledge....again!

Not a Webber but a Rochester Qaudrajet.

achris · Jun 10, 2013

Re: Mercruiser 4.3 lx WOT

dozerII said:
Not a Webber but a Rochester Qaudrajet.

That's 2 I got wrong in this thread... Not doing too well am I... :facepalm:...:shame:

Ok.. I seem to remember something about a couple of plugs in the bottom of the Rochesters that are known to leak... Maybe someone else can confirm that for us...

What Carb did you replace it with? Same, or an Edelbrock 1409?

Chris.......

dozerII · Jun 10, 2013

Re: Mercruiser 4.3 lx WOT

The same one.

dozerII · Jul 18, 2013

Re: Mercruiser 4.3 lx WOT UPDATES

Re: Mercruiser 4.3 lx WOT UPDATES

This is really starting to become irritating. The new carb I ordered (from long time US Rebuilder) was installed along with a new Carter fuel pump. Took the boat out for a test spin and it run worse than ever. Fuel delivery is right on, but the motor ran so rich it covered the back of the transom with soot. I tried to contact the carb rebuilder to no avail, supposedly it had been run on a 4.3 and fully tested with a life time warranty. After waiting for a response and reading on hear about not going with aftermarket carb rebuilder because the don't use the right jets and metering rods, I broke the seal on the carb and took it apart. No wonder it was running rich, the jets were 71's not 66's and the metering rods and tubes were the same. I took the jets, rods and top from my OE carb and made one with the right parts. I rechecked the compression and it is between 140 and 145 across the board. Timing is at 9 btdc at idle in forward, I don't have a timing light that will allow me to check for total advance, does this act up very often with the Thunderbolt ign?? The motor runs real well now and I am getting 4600 wot with a 14 3/4 X 21p prop at only 37 mph. I can't trim up much at all or the prop will blow out and cavitate, and to turn I have to trim almost all the way down.
I have a couple of friends with 4.3's in glass boats that weight 800 to 1200lbs more than my aluminum one with less HP that can run circles around me.
Anyone got any ideas?
Thanks, and sorry for the long winded update.

Bondo · Jul 18, 2013

Re: Mercruiser 4.3 lx WOT UPDATES

Re: Mercruiser 4.3 lx WOT UPDATES

dozerII said:
This is really starting to become irritating. The new carb I ordered (from long time US Rebuilder) was installed along with a new Carter fuel pump. Took the boat out for a test spin and it run worse than ever. Fuel delivery is right on, but the motor ran so rich it covered the back of the transom with soot. I tried to contact the carb rebuilder to no avail, supposedly it had been run on a 4.3 and fully tested with a life time warranty. After waiting for a response and reading on hear about not going with aftermarket carb rebuilder because the don't use the right jets and metering rods, I broke the seal on the carb and took it apart. No wonder it was running rich, the jets were 71's not 66's and the metering rods and tubes were the same. I took the jets, rods and top from my OE carb and made one with the right parts. I rechecked the compression and it is between 140 and 145 across the board. Timing is at 9 btdc at idle in forward, I don't have a timing light that will allow me to check for total advance, does this act up very often with the Thunderbolt ign?? The motor runs real well now and I am getting 4600 wot with a 14 3/4 X 21p prop at only 37 mph. I can't trim up much at all or the prop will blow out and cavitate, and to turn I have to trim almost all the way down.
I have a couple of friends with 4.3's in glass boats that weight 800 to 1200lbs more than my aluminum one with less HP that can run circles around me.
Anyone got any ideas?
Thanks, and sorry for the long winded update.

Ayuh,... Try a different smaller prop,...

dozerII · Aug 5, 2013

Mercruiser 4.3LX WOT NOW WHAT???

Mercruiser 4.3LX WOT NOW WHAT???

Okay another update on this carb issue. Like I said in my last post I found the National Carburators carb had the wrong jets and needles in it, so I combined my old and new carbs to get one that works. I have also since found out that my tach is out some and I am getting the proper WOT.
My problem now is if I try to launch hard on take off the motor just falls on it's face, if I accelerate slowly it run excellent. A I right to think I should just order the right carb and fix it after I have already payed my learning tax..
The tag on the original carb is 3304-9354 This cross's to a Sierra 189604-1 Should I buy this one ore what is recommended?

Thanks guys, I need to get this sorted.:loco:

dozerII · Aug 5, 2013

Re: Mercruiser 4.3LX WOT NOW WHAT???

Re: Mercruiser 4.3LX WOT NOW WHAT???

Can anyone tell me if Edlebrock makes a 1409 spreadbore, or do you have to use an adapter?

Bondo · Aug 5, 2013