Mercruiser 3.0 flooding

Hello

I have what seems like a common problem but I couldn't find a solution. So anyways I ran my engine (2000 3.0) after a carb rebuild. First time after rebuild fired up, no issues, runs great. Ran it the next day, to make sure before going out boating, and it ran great for 15 mins or so and then it started sputtering and stalled. I pulled the flame arrestor off and the venturis where pouring fuel into the air horn, the level of gas in the carb was almost level with the bottom of the venturis, it was that full. Of course during the rebuild I put in a new needle and seat, I used the spring loaded one. I set the float to 14mm and 27mm with the gasket. I just took out the needle and the end of it was ripped off! So why would the thing get ripped off? Before the rebuild it started doing the same thing. Could I use the old needle as a temporary fix? Is there a way to bench test the needle and seat before putting it together? Also how do I test the float? Maybe that is the problem?

Second thing I found was the rod that should activate the power valve was bent. could I just bend it back close enough? What would the symptoms of the power valve not working properly be?

Never heard of a needle ripping like that, so it most likely won't happen again.

That power valve rod has to be where it's supposed to be or the carb will run rich.

If you want to bench test the carb, borrow an outboard gas tank, connect it up, and pump the bulb hard. The carb should not leak.

Jeff

re: "Could I use the old needle as a temporary fix? " 2000 is pre ethanol days and carb point not likely ethanol resistant... Did you replace or at least clean the needle seat? Could be ethanol related degradation crap on the seat.

ok thank you, will try that. There is one nut when mounting the carb that is a PITA to get at, so the primer bulb trick should help.

sandkicker said:

re: "Could I use the old needle as a temporary fix? " 2000 is pre ethanol days and carb point not likely ethanol resistant... Did you replace or at least clean the needle seat? Could be ethanol related degradation crap on the seat.

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I bought a carb kit, OEM mercruiser one, new needle and seat was part of the kit.

So I put the old needle in to see what it would do. I got a primer bulb from my POPtimax and connected it to the carb. No matter how hard I squeezed, it would not fill the carb. So I took out the screws holding the top on, and it turned out the needle was stuck in the up position. Instant red flag for me here. So I just gave it a tap and it fell down. So I put the screws back in, pumped it up, and fuel was going in. BUT this time it did not stop and started pouring out the venturis. So that needle is clearly binding up and giving me grief. Now what would cause it to bind up like that? If I take the float out and hold it with my finger, then let go it falls out every time!

So I couldn't figure out what the heck was going on with the needle valve. Then I took the top off the carb and flipped it upside down. I let the float fall down and connected the fuel line. I squeezed the fuel bulb and if I squeezed hard enough, the float would pop up and gas would shoot around the needle. If I didn't push so hard then it would seal the hole and no gas cam through. So now I have two options. Option one is the fuel pump is making too much pressure, option two is to set the float lower. I am starting to think that the first option is the culprit. How do I adjust and check the fuel pump pressure? Please advise. Thanks.

I put the carb in, this time POSITIVE that the needle was ok and the float set up right. Well I started cranking and before it could fire it's flooding AGAIN! AARRRGH! so I went ahead and started loosening the soft brass fuel fitting at the carb and gas started spraying out! Definitely the float is trying to seal but there is pressure, I think too much pressure. Going to take apart the pump into tiny bits, does anyone know HOW it controls the pressure? maybe some relief hole is plugged. How do I fix this??? I have a buyer for my boat coming soon and it needs to run good before he comes!

Ok I need a new pump it seems. I will go to the auto parts store, what make and model of pump do I tell them? If I say mercruiser they obviously will say they don't have it. I think maybe carter pump? please help!

vroomZOOM said:

Ok I need a new pump it seems. I will go to the auto parts store, what make and model of pump do I tell them? If I say mercruiser they obviously will say they don't have it. I think maybe carter pump? please help!

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If you can go to a Napa they carry Sierra marine parts. You need a marine pump not an automotive one. Carter does make marine pumps but really any marine rated pump will be ok

I use a q-tip and some brasso to clean seats. Did you replace seat ?

yes I replaced the seat. I need to sell this boat before the season ends so I went ahead and bought a new pump. Went to put it in and the inlet on the pump is one the other side (same side as the outlet). Old pump had the inlet on the opposite side. anyways I am getting more fuel line now so it will reach the new inlt location it should work ok but now I have to find fuel line! UGH! will this thing ever work????

ok got some fittings and marine grade hose and now it fires up and doesn't flood, so the fuel pump was the culprit all along. After pulling apart the pump I found out why they upset the needle in the carb. It's called a PULSATION DAMPER. there is a little diaphragm after the main pumping diaphragm and it's got a little air chamber that acts sorta like a cushion to smooth out the pulses from the pump. if there is a hole in the second diaphragm then there is no air cushion to absorb the pulses and the pulses upset the needle and flood the carb.

Anyways now I have another issue. if I slowly rev up at 2000 rpm it will die. If I hit it and get past 3k it's ok up to WOT. so between 2000 and 3000 it will die, anything else and it's ok. What should I look for?

Rebuild it again. Likely didn’t clean out the idle transition circuit. If you slam the throttle forward power valve will open to add some fuel likely overcoming lean spots in the transition circuit. Make sure it 8s getting soaked in cleaner and either put a small wire through every single passage and oriface in carb if you can use an ultrasonic cleaner with carb cleaner so much the better