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Mercarb 2bbl Flooding after engine is killed

Bum

Member
So, last summer I had this same issue. Stop the engine and fuel would drip down, then the boat didn't want to restart until all the fuel evaporated or I opened up the throttle to let it air out. Last summer I installed a new needle, seat and float. Adjusted everything and the flooding problem stopped.

Today I pulled the tarp off the boat, reinstalled the points and changed oil. Had a hard time getting the engine started, but some starter fluid seemed to work. I killed the engine and fuel was dripping into the carb at a much higher rate then when I had the issue last year. A very fast steady drip.

I pulled the carb off, checked the needle and seat. Readjusted the float to 14mm and 27mm drop. I am currently using the spring. As that is what was in it when I first tore it apart last year.

So, is there some other adjustment I need to make? Is the float adjustment I found incorrect? I measured from the bottom dot on the float to the rim of the carb.

Any help is appreciated.

Thanks,
Bum
 
What’s your fuel pressure. If fuel pressure is too can cause this as well. Also possible float is fuel soaked and needs replacement
 
What’s your fuel pressure. If fuel pressure is too can cause this as well. Also possible float is fuel soaked and needs replacement


The float was replaced less then 12 months ago. I doubt it would have gone bad already.

How would I go about testing fuel pressure? I don't think I have the equipment for that.
 
One thing I left out of my original post. I actually pulled the carb off twice. After the first time I took it off I just adjusted the float a little down. When I put the carb back on I was not getting any fuel to the jets, and the boat wouldn't run at all. When I unbuttoned the top of the carb before removing the whole thing, there was something like a pressure release or vacuum release from the bowl side. I'm assuming this would be normal if the carb was sucking air out of the bowl instead of fuel?
 
Not sure which Serial you want, I found 2 on the carb cover. MerCruiser Drive unit- 0c502866 and Transom- 0C57414A. 88 Sea Ray.
 
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Thanks for the diagram. I found info someplace that the drop needed to be 27mm, so I will readjust that. The needle and seat was replaced less then 12 months ago. I'll make sure there is no crud somehow causing problems.
 
may wanna check the sight tube, from the fuel pump, to make sure it is dry.....

I haven't checked yet, been busy today. But what would fuel in the sight tube indicate? That is the tube running form the side of the carb down to the pump correct?
 
Also check your CARB inlet filter.

if it has sediment in it that may be your issue.

The fuel pump should produce only ~ 6 to 7 psi max so if you can check this that would also help.
It would require you to either cut the current fuel line to insert a tee for gauge or remove steel line and substitute a soft line with a gauge teed into it between pump and carb. (this requires adapter to carb threads........) so if you could get your hands on an old Mercruiser fuel line for that engine somehwere you could cut that and adapt Tee for gauge as it would have the correct fittings on both ends.

I understand you are seeing dripping after shut down but the condition is about the same as dripping at idle. Fuel level may be to high based on needle not seating.

I think you can get to float thru top cover? if you can with a small pic tool or thin piece of wood to check fuel level then you could possibly see what your fuel level is.
 
I haven't checked yet, been busy today. But what would fuel in the sight tube indicate? That is the tube running form the side of the carb down to the pump correct?

Yes, bright yellow TYGON if its in good shape.....if its wet, it means the diaphragm in the fuel pump is leaking and needs attention. The tube is there to route that fuel that leaks back to the carb to minimize the risk of explosion.....usually, you can see the fuel entering the throat of the carb with the engine running....
 
Yes, bright yellow TYGON if its in good shape.....if its wet, it means the diaphragm in the fuel pump is leaking and needs attention. The tube is there to route that fuel that leaks back to the carb to minimize the risk of explosion.....usually, you can see the fuel entering the throat of the carb with the engine running....

I missed that comment..................UGH...............That could be his only issue.

Fuel in yellow tube = Fuel pump.

REPLACE
 
I took the carb apart again and found some debris in the seat. I think it may have fallen in from all the crap blowing around the air right now. Should have done a better job of making sure everything was cleaned out before putting it together.

Now I just need to figure out why my idling is wonky. If I get it to idle around 650rpm it will eventually bog down and die. Almost like it ran out of gas. I have to pump the throttle before it will restart. It will then idle for several minutes before bogging down and dying again. If I increase the idle to closer to 800 rpm it seems to idle as long as I want, but the rpms jump up and down 150-200 rpm. Not sure what is causing the fluctuation. I may change the points to a new pair I have just to make sure they aren't causing a problem.
 
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