Mercruiser 3.0 diagnosis / serial number decode

[achris]

2. Here's the red tag on my carb. Reads 1389-9562.

That's a Mercarb. The 'gasket set' for that is part# 3310-810929004

Chris......
(I've pull the service pages out of the manual and attached them...)

 

[Tube1]

Thanks again Chris. Got the carb pulled and fully disassembled following Mike’s video. Most of the parts are soaking in carb cleaner.

Everything looked pretty good with little carbon residue. However there’s two things I noticed that are concerning:

Needle that goes in the seat (?) was very dirty and gummed up on the tip

I don’t have the spring that goes behind the fuel inlet filter. How critical is this spring and would this hinder fuel flow? It was never in the carb.

 

[achris]

Needle that goes in the seat (?) was very dirty and gummed up on the tip

There's the reason there's no fuel in the carb. The fuel level is controlled solely by the needle and seat. If it's gummed up, it'll stick, no fuel.

I don’t have the spring that goes behind the fuel inlet filter. How critical is this spring and would this hinder fuel flow? It was never in the carb.

The spring is to keep the filter against the inlet so all the fuel will flow through the filter. Should the filter become clogged the pump should produce enough pressure to push the filter back and allow enough fuel into the carb for it to keep running. No spring means the filter isn't filtering....

Chris.......

 

[Tube1]

I got a rebuild kit in today and it appears I successfully rebuilt the car. However still having issues. I can get the engine to run by pouring gas down the carb. The accelerator pump also works now, but I have to dump gas manually into the float bowl. I’m getting fuel pressure, but something in the puzzle is missing as gas isn’t being pumped into the float bowl.

The only thing I can think is I still don’t have the spring for the carb inlet fuel filter. Would this just cause the filter not to work, or completely restrict gas flow?

 

[Tube1]

I’m getting like no fuel pressure while engine is idling. Starting to think something is up with the pump. Does this look like the correct orientation?

 

[Tube1]

 

[Eric 3.7LX Alpha 1]

I got a rebuild kit in today and it appears I successfully rebuilt the car. However still having issues. I can get the engine to run by pouring gas down the carb. The accelerator pump also works now, but I have to dump gas manually into the float bowl. I’m getting fuel pressure, but something in the puzzle is missing as gas isn’t being pumped into the float bowl.

The only thing I can think is I still don’t have the spring for the carb inlet fuel filter. Would this just cause the filter not to work, or completely restrict gas flow?

I believe not having the spring would allow fuel to bypass the filter, as if it were clogged. You could always remove the filter completely for testing purposes.

If the fuel bowl is empty, and the float is down, and needle valve is lifted off the seat, you should be able to blow air with your lungs into the carb if you connect a length of hose to the inlet, even if rigged up. If you can't blow in there's got to be a restriction between it and the needle valve/seat, or the needle is closed. While it was apart, did you try to blow air or carb cleaner in the inlet and see it come out the hole where the needle valve is? When I do mine, I blow in the inlet and move the float up and down by hand to ensure the needle seats and shuts off gas, and also opens back up.

 

[Eric 3.7LX Alpha 1]

I added a mechanical fuel pressure gauge inline between my pump and carb, to verify fuel pressure if I ever had an issue while running. I have since removed it though due to the weight of the fitting and vibration, it eventually would cause one of the flare ends to split and leak. I may re install it but down lower on the outlet of the fuel pump using the NPT threads of the pump and a small pipe nipple, would be stronger than the flare line. It was great to eliminate or know right away if the engine was not getting fuel.

 

[dubs283]

Does this look like the correct orientation?

Yes, but the actuator arm for the pump looks short/broken

 

[Tube1]

I just tried blowing air into the carb fuel supply inlet and it’s completely stopped up. What should I verify when I take it apart again? The seat and needle?

 

[Tube1]

Air should be able to be blown freely through the supply inlet and through the seat. Is that correct? I’m not getting any airflow through this pathway if that’s how it should work

 

[Tube1]

 

[achris]

With the needle out you should have unrestricted flow through from the inlet out through the seat. If that's blocked, unscrew the seat and find out why.

Chris...

 

[banderberg]

take points to NAPA, guy behind counter will come back up with a new set of points and a condensor. pay the guy and proceed home

or simply file the points (required if they sit for any length of time), then set dwell and timing.

So by the points do you mean the whole metal plate or just the little arm that contacts? I'd like to replace mine too.

 

[achris]

So by the points do you mean the whole metal plate or just the little arm that contacts? I'd like to replace mine too.

These are the points...

 

[Tube1]

I was incorrect. I am getting flow through the main inlet and through the needle/seat, but the bowl is not filling. At this point I’m fed up with it… tried my best to rebuild the carb but somethings still off.

I’m getting solid pulses of fuel out the supply line while the engine is cranking so pump is good. I think the bowl is not filling because there’s a restriction in the carb blocking the whole system, and I’ve exhausted my options with the knowledge I have.

What’s the best place to get a rebuilt carb? Or a service I can send mine to?

I really did think I had this thing rebuilt correctly. I was very tedious and took my time inspecting everything

 

[Scott Danforth]

I was incorrect. I am getting flow through the main inlet and through the needle/seat, but the bowl is not filling. At this point I’m fed up with it… tried my best to rebuild the carb but somethings still off.

I’m getting solid pulses of fuel out the supply line while the engine is cranking so pump is good. I think the bowl is not filling because there’s a restriction in the carb blocking the whole system, and I’ve exhausted my options with the knowledge I have.

What’s the best place to get a rebuilt carb? Or a service I can send mine to?

I really did think I had this thing rebuilt correctly. I was very tedious and took my time inspecting everything

Your float level or the needle and seat

 

[Tube1]

I’ve done some thinking after wanting to throw the carb across my yard, and the only thing I forgot to verify was float drop. It’s possible my needle is shut because of this. Literally everything else in that carb is spotless and flows freely.

 

[Tube1]

well guys, I was so far in to this project that I absolutely refused to give up. I took the carb apart and found that the needle was stuck in the seat. Brand new parts.

As everyone told me, ONLY buy OEM kits. I ordered a cheap one off Amazon because it would get here to meet the timing I wanted.

After addressing this issue and using my old seat/needle, the boat fired up almost instantly.

Cheers everyone and thanks for all the help. One of the most helpful forums I’ve been on and I’ll be sure to post some pics of the boat out on the water after I get all the other maintenance items sorted!

 

[achris]

well guys, I was so far in to this project that I absolutely refused to give up. I took the carb apart and found that the needle was stuck in the seat. Brand new parts.

As everyone told me, ONLY buy OEM kits.

And now you know why.

I ordered a cheap one off Amazon because it would get here to meet the timing I wanted.

Old Chinese proverb. 'Cheap no good, good no cheap'...

After addressing this issue and using my old seat/needle, the boat fired up almost instantly.

Best news I've heard all day!

Cheers everyone and thanks for all the help. One of the most helpful forums I’ve been on and I’ll be sure to post some pics of the boat out on the water after I get all the other maintenance items sorted!

We'll always be here for you...