3.0L mercruiser bogging down at speed

[craigboy]

Re: 3.0L mercruiser bogging down at speed

YES! gas blasted all the way back to the bellows. Checked the screen while i was in there and its still brand new with very little brownish material trapped by the screen. It even tried to start up.

I have some pictures of the card because i am trying to identity it. going off what i have seen on the web ....

"The part number for the Mercarb is on the side of the float bowl, on the fuel inlet side.
On the Rochester the part number is XXXXX on the throttle lever side above the secondary shaft." But I cant see any.

 

[alldodge]

Re: 3.0L mercruiser bogging down at speed

YES! gas blasted all the way back to the bellows. Checked the screen while i was in there and its still brand new with very little brownish material trapped by the screen. It even tried to start up.

I have some pictures of the card because i am trying to identity it. going off what i have seen on the web ....

"The part number for the Mercarb is on the side of the float bowl, on the fuel inlet side.
On the Rochester the part number is XXXXX on the throttle lever side above the secondary shaft." But I cant see any.

Sounds good, fuel is making it to the carb.

From you previous post #15 you said, the engine ran fine for about 25 minutes total, including putting the gas cap back on. On the third start time it would not start. I'm thinking the vet may be clogged and not letting air into the tank. If this is the case the fuel pump will draw a vacuum on the tank and then be unable to draw fuel. Run it long enough to get it to the point it will not start. Once there make sure the choke plate is fully open and pump the throttle to see if fuel is being squirted in by the accelerator pump. If it isn't remove the gas cap and listen for air being sucked in.

 

[craigboy]

Re: 3.0L mercruiser bogging down at speed

SO, I just pulled the trigger on a new carb. So i will have to update this thread on that. I have to say that my problem solving is a little lacking in compunction on this boat, But i am running out of time . I have till the 15th to get this boat ready for the fishing trip with my kids.(this is important because I am out of country often)
However in my problem solving, I failed to rule out electrical. (I put in new plugs and dis.cap./rotor) but maybe its the coii? I am thinking OF maybe i have a electrical problem like the thermostat .

 

[alldodge]

Re: 3.0L mercruiser bogging down at speed

I see nothing so far that tells me it's the carb, plugs, distributer cap or wires, your throwing parts at the problem. Need to find out if the fuel pump is working and whether there is a fuel restriction. Need to find out if the carb is getting fuel, and of sufficient quantity and pressure. If it was electrical it wouldn't bog down as mentioned in your first post, it would die quick.

 

[EL-BATO]

Re: 3.0L mercruiser bogging down at speed

Any updates on this?

 

[flash3610]

I ran across this thread while troubleshooting a different problem with my 3.0LX and thought I would offer a couple of suggestions based on the assumption that the stalling is due to flooding and not starving due to the fact that fuel is getting to the carb and unless the needle valve is stuck closed I can't see how it could be starved.

1.) If the mechanical fuel pump was recently replaced, it may be that the spacer was not used with the new pump. My 1997 3.0LX has this spacer between the pump and the block that ensures that the pump operates at the proper pressure (I think around 6 psi). Without the spacer it runs at around 15 psi and will overcome the needle valve and flood the engine. If you lost the spacer, I am not sure where to find a replacement but I haven't looked real hard. It doesn't show up in mercruiser diagrams.

2.) Make sure the flame arrestor is clean. My flame arrestor was clogged and acted as a choke and flooded the engine after it got up to operating temperature. Idled fine with the arrestor removed, shut down the engine, replaced the arrestor, started again and flooded within 5-10 minutes . Cleaned the arrestor and had a great summer

I would be curious to hear if this problem is solved.

 

[bigcountry70]

I ran across this thread while troubleshooting a different problem with my 3.0LX and thought I would offer a couple of suggestions based on the assumption that the stalling is due to flooding and not starving due to the fact that fuel is getting to the carb and unless the needle valve is stuck closed I can't see how it could be starved.

1.) If the mechanical fuel pump was recently replaced, it may be that the spacer was not used with the new pump. My 1997 3.0LX has this spacer between the pump and the block that ensures that the pump operates at the proper pressure (I think around 6 psi). Without the spacer it runs at around 15 psi and will overcome the needle valve and flood the engine. If you lost the spacer, I am not sure where to find a replacement but I haven't looked real hard. It doesn't show up in mercruiser diagrams.

2.) Make sure the flame arrestor is clean. My flame arrestor was clogged and acted as a choke and flooded the engine after it got up to operating temperature. Idled fine with the arrestor removed, shut down the engine, replaced the arrestor, started again and flooded within 5-10 minutes . Cleaned the arrestor and had a great summer

I would be curious to hear if this problem is solved.

Any update? I have problem like yours. I am getting 6 psi out of pump.

 

[bigcountry70]

I am looking for an update on this, I am having a problem just like yours. I have not thrown money at the carburetor yet but that’s my next I did as well.