merc 20 hp 4 stroke carb issue

ClemsonAlum · May 6, 2021

Hmm. Since you said the slow speed jet was clogged and you cleaned it, and it ran better, I bet the high speed jet or passage is partially clogged still. Don't know how else to explain running better with choke on at high idle, with the bowl full of fuel, with fuel getting purged out. Assuming you are 100% sure that it is leaking out of the overflow hole. Run mono fishing line in there ? Or a get a carbuerator brush set? Even if the fuel pump was somehow giving too much fuel, you would think the float/needle would seat when the bowl got full and it would run without choke?

-Kurt

marlattrr · May 7, 2021

I ran a paper clip in and out. Sprayed carb cleaner and air through it. I can see through the hole of the main jet.

Thanks for sticking with me guys!

RaisedByWolves · May 7, 2021

ClemsonAlum said:
Hmm. Since you said the slow speed jet was clogged and you cleaned it, and it ran better, I bet the high speed jet or passage is partially clogged still. Don't know how else to explain running better with choke on at high idle, with the bowl full of fuel, with fuel getting purged out. Assuming you are 100% sure that it is leaking out of the overflow hole. Run mono fishing line in there ? Or a get a carbuerator brush set? Even if the fuel pump was somehow giving too much fuel, you would think the float/needle would seat when the bowl got full and it would run without choke?

-Kurt

Something isint adding up.

Im wondering about the carb gasket or a possible manifold leak at this point.

This could easily be more than one problem.

marlattrr · May 7, 2021

I replaced the gaskets.

The only thing I didn't replace is the accelerator pump assembly.

nccatfisher · May 7, 2021

marlattrr said:
I replaced the gaskets.

The only thing I didn't replace is the accelerator pump assembly.

^^^^^^^ I am assuming what you are describing here is the choke?

RaisedByWolves · May 7, 2021

marlattrr said:
I replaced the gaskets.

The only thing I didn't replace is the accelerator pump assembly.

How tight did you tighten the bolts?

A little counterintuitive, but over tightening the bolts can also cause a leak, even on a new gasket as it deforms the mounting surface deforming the gasket.

RaisedByWolves · May 7, 2021

nccatfisher said:
marlattrr said:

I replaced the gaskets.

The only thing I didn't replace is the accelerator pump assembly.

Click to expand...

^^^^^^^ I am assuming what you are describing here is the choke?

Im thinking primer, which could cause issues he described.

nccatfisher · May 7, 2021

Im thinking primer, which could cause issues he described.
[/quote]Yep, I am still old school and call them chokes but you are correct. I was wondering if that may be the root of his evil. I know if you don't fully close/shut them off they will allow air in the system and cause all kind of problems.

marlattrr · May 10, 2021

how do i adjust or check that primer? i backed off the nut so that its not engaging at all and i still have the problem

RaisedByWolves · May 11, 2021

marlattrr said:
how do i adjust or check that primer? i backed off the nut so that its not engaging at all and i still have the problem

Not being familiar with that motor I couldn't hazard a guess.

You could try and disassemble it and look for a torn o-ring or diaphragm etc.

Something causing your issues should stand out.

marlattrr · May 11, 2021

New carb from Amazon and shes purring like a kitten again.

Idk whats wrong with the old carb but that did it.

RaisedByWolves · May 13, 2021

Well, at least we were on the right track. :wink:

marlattrr · May 13, 2021

Thanks for all the help everyone.

By the way-wolves. Im just one county north of you in Lehigh.

zgriff19 · Sep 16, 2024

marlattrr said:
Thanks for all the help everyone.

By the way-wolves. Im just one county north of you in Lehigh.

Having the exact same issue! Do you happen to have a link for the carb you purchased on Amazon?

merc 20 hp 4 stroke carb issue

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