1993 Mercruiser v6 4.3 carburator.

dlogvine

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I'm finishing this engine rebuild, but encountered a problem. Original engine had a quad barrel carburetor (Weber was inside when i bought the boat). However this carburetor was shut and seized completely and beyond repair. So i bought another marine carburator matching the intake manifold. This is a Rochester 4mv one of its instances. I rebuild it, put new gaskets, needle and jets. But when i started cranking the engine I got some fuel overflowing. I wondered if it could be due to the electric fuel pump creating more pressure than the needle can take and it pops it up, thus continuing the fuel flow even when the float is supposed to shut it. Or could it be something with the carburetor rebuilt? I took it out and reassembled a again. Also since there was fuel leak into the cylinders, there is a problem with engine crank and I managed to remove 3 plugs, the other 3 I will try to remove tomorrow if there is still fuel in the remaining cylinders and the engine is not cranking. Or should I let the fuel evaporate over night since there is no carburetor? Sorry for the long post, just wanted to put all my questions in one post. Thx for help
 

dlogvine

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oh, by the way, 1993 Mercruiser 4.3 v6 according to the manuals should come with a 2bbl carburetors.
 

Scott06

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Either fuel pressure is too high , which can be measured and should be below 7 psi. Or float and needle and seat ar not working float can be water logged/damaged and needle and seat can have debris or be damaged. Either way I'd take the plugs out and spin the engine to expel any gas in the cylinders
 

Bondo

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oh, by the way, 1993 Mercruiser 4.3 v6 according to the manuals should come with a 2bbl carburetors.

Ayuh,.... The 4.3l came with both the 2bbl., 'n the 4bbl. carbs,....

The carb ya put on is a step backwards from the Merc/ Weber ya took off,....
The Edelbrock 1409 is a carbon copy of the original carb that came on yer motor,....
The Quadra-jet ya put on, is what Merc used to use, before the Weber,....
 

alldodge

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if there is still fuel in the remaining cylinders and the engine is not cranking.

The fuel will leak down the cylinder walls, IF its fuel. You sure its fuel and not water?

Either way I'd take the plugs out and spin the engine to expel any gas in the cylinders

Agree, get those other plugs out and crank it over ASAP
 

dlogvine

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Got the engine running today with my friends help. The plugs I removed all and let the gas evaporate. The problem appeared to be in the linkage from the throttle lever. It was too tight and was keeping the carburetor pump open, which was causing the fuel overflow. removed the likage and with a little of the starter fluid got it running. Now there is a problem with the throttle lever. Looks like the lever is not working correctly, the linkage looks too short and the direction is reversed. When I push the lever forward it closes the carb pump and vice versa. I recalled that when I was upholstering the panels I removed the throttle control and took out the back plate. Then I reassembled it but without the diagram, looks like, did it incorrectly. So i wonder, if anybody can either post the diagram or send the link to it, so that i can reassembe it correctly. The control is Quicksilver older version, ill post a picture of it, not sure about which model. Thx
 

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dlogvine

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Issue resolved, the throttle control box was not assembled correctly when I took it apart (accidentally when removing the side panel). The linkage was not installed properly and was causing the lever to work in reverse order and also shortened the cable significantly. After reassembling it correctly all the problems were fixed including overflowing carburator (caused by opened acceleration pump due to the short link cable) and the engine is working perfectly. Might still have to check the torque on the rockers.
 

Maclin

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I doubt that the carb staying open was the cause of fuel bowl overflow. The accelerator pump only pumps as the throttle is moved forward from idle. Once the throttle stops moving the pump cannot keep squirting fuel. Good luck, I hope the carb keeps behaving :)
 

dlogvine

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Looks like after the throttle control and cables adjustment everything works fine. I might need to adjust the rockers if they will be clicking and running noisy. Thank you.
 

Rick Stephens

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Throttle pumps are a plunger in a cylinder with a check ball on the bottom. The only way you leaked fuel is is the check balls are crudded up or the carburetor was overfilling for whatever reason. I would recommend you kit the thing and make sure.

Rick
 

Bondo

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Ayuh,..... Agreed,.... The Cure don't fit the symptoms,....
 

dlogvine

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Hmmm, the throttle cable that is too tight will continuously pull the carburetor accelerator pump down. Doesn't that mean that more fuel is getting down in the carburater? It is the same as having the throttle on max gas. Unless I'm missing something completely...
 

Rick Stephens

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Hmmm, the throttle cable that is too tight will continuously pull the carburetor accelerator pump down. Doesn't that mean that more fuel is getting down in the carburater? It is the same as having the throttle on max gas. Unless I'm missing something completely...

Nope. It is a pump. It only activates when throttle is added. It has to come back up to refill it with gas.

Your tight throttle cable just makes the idle go up. It does not effect the throttle pump at all except make it less effective since it can't go all the way back up and refill entirely. If a tight cable could cause the accelerator pump to give more fuel constantly, then so too would setting the throttle up a bit past idle.

The accelerator pump only does anything during and when throttle is opened..
 
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