Mercruiser 350 5.7 mech fuel pump question

Flyboy42880

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I have a '96 19' Celebrity with a 350 5.7 liter. It has been hard to start after it's up to running temp and then sat for an hour or so. Has a rebuilt 2 barrel Rochester on it. Almost seems to be flooding out on warm starts. I did a little trouble shooting trying to find something obvious. What I found was a clogged vent or suction line that runs from the back of the mech fuel pump up to the top of the carb. Not the fuel lines... Boat cranks right up cold and even in between ski runs. Seems to only be a problem after sitting for an hour.

First, what does this tube actually do? And would this be the prime culprit for my problem? Any help is always greatly appreciated!
 

alldodge

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Re: Mercruiser 350 5.7 mech fuel pump question

I have a '96 19' Celebrity with a 350 5.7 liter. It has been hard to start after it's up to running temp and then sat for an hour or so. (1)Has a rebuilt 2 barrel Rochester on it. Almost seems to be flooding out on warm starts. I did a little trouble shooting trying to find something obvious. What I found was a clogged vent or suction line that runs from the back of the mech fuel pump up to the top of the carb. Not the fuel lines... (2)Boat cranks right up cold and even in between ski runs. Seems to only be a problem after sitting for an hour.

(3)First, what does this tube actually do? And would this be the prime culprit for my problem? Any help is always greatly appreciated!

(1) Who rebuilt the carb?
(2) The carb sounds to be flooding the engine
(3) That tube lets you know if your fuel pump has a ruptured diaphragm. If you ever find fuel in the line, you need to replace your fuel pump
 

Flyboy42880

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Re: Mercruiser 350 5.7 mech fuel pump question

It was a carb shop in California... Can't remember the name of it. So what adjustment should I start with. I agree, I think it's flooding out as well.
 

alldodge

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Re: Mercruiser 350 5.7 mech fuel pump question

It was a carb shop in California... Can't remember the name of it. So what adjustment should I start with. I agree, I think it's flooding out as well.

I would check the float level, may be a bit to high. You could run it and after shutting it off, look down the carb and see if you see fuel dripping. If there is dripping then you either have a bad needle seat or float level is to high
 

alldodge

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Re: Mercruiser 350 5.7 mech fuel pump question

No dripping that I can see....

Your choke plate is staying full open when warmed up, right? Also if you try to give it a pump when warm it still doesn't want to start?
 

Bondo

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Re: Mercruiser 350 5.7 mech fuel pump question

I have a '96 19' Celebrity with a 350 5.7 liter. It has been hard to start after it's up to running temp and then sat for an hour or so. Has a rebuilt 2 barrel Rochester on it. Almost seems to be flooding out on warm starts. I did a little trouble shooting trying to find something obvious. What I found was a clogged vent or suction line that runs from the back of the mech fuel pump up to the top of the carb. Not the fuel lines... Boat cranks right up cold and even in between ski runs. Seems to only be a problem after sitting for an hour.

First, what does this tube actually do? And would this be the prime culprit for my problem? Any help is always greatly appreciated!

Ayuh,.... Welcome Aboard,... Pull the Spark plugs, 'n see their Color,....

If it's runnin' Rich, 'n Floodin',... The plugs will be Black, 'n Sooty,...
 

Flyboy42880

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Re: Mercruiser 350 5.7 mech fuel pump question

Yep, full open when warm. Seems to flood it when I even half pump it.
 
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