Mercruiser 3.7 Quadrajet Flooding Out - Help I am 11 months into this!

R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
Hello,

After rebuilding a 20' cuddy, 3.7 L 190 HP engine, and outdrive, last step was the quadrajet carb (17083522) as the idle pickups were plugged up. I also replaced the fuel pump (with the thick gasket) bottom down bowl.

On rebuild, I flooded the carb out something fierce. I figured I was still high on fuel pressure as the needle/seat had passed a leakdown test, so I installed a Holley fuel pressure regulator that holds 4.5 psi. WHen I pull the carb off there is fuel sitting in the intake and the bottom of the primary throttle plates.

DO date, I have broken down this carb probably 20 times. I have checked or verified the following:

-no leaks from pressed plugs
-secondary windup set at 1/4 turn load
-0.190 choke pulloff
-proper needles/jets/secondaries/hangers
-float set at 3/8 (I have played with 1/4" to 3/8")
-Float weight within spec
-Needle hook is no longer there, so I did not install it improperly with it hooked onto the float
-good spark
-4.5 psig fuel pressure regulated down (manual states 3-6 psi good)
-6 degrees of timing
-good compression on all cyclinders.

I have actually pulled the carb apart and tried to verify that the float does seal with water at 5.5 psi of air, which it does.

I do not know what else I can do to rule this out or fix this. Any ideas on what I may be missing here? I am at my wits end with this, and have now pretty well resigned myself to not going out this season because of this. I really regret changing the pump and carb at the same time, but now this is history and I need to try and unravel this now as I do not have the old pump any longer.

THanks in advance for your help

Ron
 
R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
I also forgot to mention I drained all the gas out and poured fresh in to rule this out (as well as flushed lines and drained/filled the carb)
 
F

four winns 214

Senior Chief Petty Officer
Joined
Oct 25, 2008
Messages
770
I hate to tell you this, but when my Quadrajet did that on a 228R, it was the fuel pump that had been replaced. All I can suggest is try adding another thin gasket to the fuel pump. When I called Merc tech support about the issue, they instantly knew the solution (thicker gasket). They didn't even have to think about it. Also, in the Merc Service Manual, there are very precise measurements pertaining to the length of the push rod that runs the pump. Good luck!
 
R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
The pump is driven off the crank I believe. I sent this to Mercruiser tech today, I am not sure if anyone out there can help me.

Dear Sir/Madam,

I have been fighting with a Mercruiser 180 3.7 for the last 11 months, and hope you can help. I had the motor and outdrive running well after a rebuild, and went to rebuild the carburetor (Rochester #17083522) following an issue with the idle circuit plugging up on me. I replaced the fuel pump at the same time. Since doing both those things on top of one another, I have been unable to get the carburetor to run without flooding out with obscene amounts of fuel, sometimes enough to pour out of the intake/carburetor gasket. When I pull the carb for the teardown, there is physically fuel in the intake, and enough to get me concerned about washing #4 cylinder out.

I have confirmed and reconfirmed the following:
-155 to 160 psig of compressor on all 4 cylinders
-good spark on each with 0.035 gap on all 4 with evidence of burning very rich
-timing at 6 degrees advance base with a Pertronics ignition (installed and operable prior to the carb rebuild). I have also checked to make sure I am not sparking on the exhaust stroke, but rather the compression
-Good fuel (have dumped and refilled twice now)

At first I suspected a leaking needle and seat, so I replaced and vacuum checked with no improvement. I ended up actually filling the bowl with water, and pressurizing to 5.5 psig with air before any leakage started. I also went back to the stock 0.120 fuel inlet need rather then the 0.135 in the rebuild kits. Same issue.

I replaced the brass float with a plastic one, no improvement. Played with idle mix adjustment from 0 turns open (3 open before the rebuild) to 4 turns open, still flooding out and every now and again running for a couple of revolutions and then dying.

At this point I suspected the fuel pump, and measured pressure at around 7 psig. I installed a Holley fuel pressure regulator and ran it between 4 psig and 5.5 psig with no improvement noted. I have the thick Mercuiser gasket installed, the pump is a Sierra with the downward facing fuel filter housing.

I bought and rebuilt another 17083522 and installed with the same issues.

I am terrifically frustrated at this point as I have pretty well tried everything I can think of. I still suspect the fuel pump is delivering too much fuel pressure and flooding out the carbs, but I can?t see how this can happen with only 4.5 pounds on the gage downstream of the Holley regulator.

I am at the point where I can?t think of what else to do other than hook up a fuel supply and hang 8 feet above the carb to get 3 psig steady to prove it will run with one of the carbs, or to replace the fuel pump again. Please offer me any advice you might have on what else I may be missing here. Thanks in advance
 
M

mr 88

Commander
Joined
Nov 3, 2010
Messages
2,224
Any reason you can't put the mechanical pump back on and try that. If it works you know what the problem is or isn't.
 
R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
Yes I have a fuel pressure gage inline showing 4 psig. I just installed a second spacer on the fuel pump to rule it out. It flooded out with either carb installed. It is behaving as if the needle and seat are leaking by, and I can't even get it to turn over any longer.

I am located outside Chicago in munster Indiana. At this point I am considering taking it to someone as frustratingly I can't fix this. I built the boat motor and outdrive but can't solve a simple carb problem.
 
R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
That is the frustrating part. I have been through 3 needle/seats, 3 floats, and visual confirmation the neele and seat hold 5.5 psi of air when off the boat. On the boat everything ceases to make sense. If I had someone with another 470 I could try the carb that way.
 
S

stonyloam

Vice Admiral
Joined
Mar 13, 2009
Messages
5,827
Ya know Occam's Razor says the simplest explanation is often the correct one. The simplest explanation is not that you screwed up twice, it IS too much pressure. I have seen threads where several people have had that exact same problem with new 470 fuel pumps. So I suspect that is what is going on here, even with the regulator. The pump runs off of the cam on a 470, and I think the lever of the pump is just too long and you are just getting too much pressure. I think you need to adjust the regulator to minimum (if it is adjustable) and measure fuel pressure ( you might be able to borrow a gauge from Autozone). I know that if mine ever goes I will go to an electric pump. One of the 470 guys here went that rout and loved it. If you are at all interested I'll see if I can find ite thread. Good luck.
 
R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
Thanks for the reply. I have a regulator installed and am showing 4 psig on the gage downstream of the regulator. That is why I am scratching my head here
 
R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
I just checked it with a separate gage. 5 psi on that gage and 4 on the other hardpiped. I have pictures of both but can't get them on here from my phone.
 
R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
2 Meg limit unfortunately. The only other thing I can think of is the wrong float as I bought the kit from the same place. Does anyone else know what the right float is for a mercruiser 180 sn 0b750749?
 
R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
Or if someone has a rebuild kit they know works for a 17083522. It won't take long to rebuild as I have had it apart 25 times...
 
R

rozicrc

Seaman
Joined
Sep 28, 2009
Messages
65
I just got done pressure testing the needle and seat with fuel in the bowl. the fuel level is about 5/8 inch from the top of the casting. This is level with the cutout for the accelerator pump. I pressure tested at 7 psig. Is the list fuel level consistent with what others would expect? I have now ruled out the needle and seat ad well as fuel pressure. Only things left are systematic mistakes during the rebuilds or too high a level.
 
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