89 mercruiser 3.7 carb flooding

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okgorilla

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Jul 3, 2011
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We've had two carburetors, one completely rebuilt, installed and the carb is still flooding. We've checked the float. It's new and set to specs. Needle and needle gasket are new and installed correctly. Timing adjusted to specs, Idle adjusted to specs, cleaned and re-cleaned the carburetor. Nothing seems to stop the carb from flooding. What else could it be? :confused:

Carb is 2 barrel mercarb with spring float valve.
 
Bt Doctur

Bt Doctur

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Re: 89 mercruiser 3.7 carb flooding

fuel logged float?. mech or elec fuel pump?
 
Eric 3.7LX Alpha 1

Eric 3.7LX Alpha 1

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Re: 89 mercruiser 3.7 carb flooding

What's the pump pressure going into the carb?

Put a inline psi gauge on it temporary to see what you are getting for psi.
 
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stonyloam

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Re: 89 mercruiser 3.7 carb flooding

okgorilla said:
Carb is 2 barrel mercarb with spring float valve.
Click to expand...

My kit came with both the spring and a solid rod (no spring) for the needle. When I took my carb apart it had the solid rod (no spring), so that is what I put back in and had no problem. Tried both and they defiantly give a different response.
 
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okgorilla

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Re: 89 mercruiser 3.7 carb flooding

We replaced the fuel pump. When we did that we finally had enough pressure to have gas spewing through the fuel line. It apparently had tiny holes in it we couldn't see before because of low fuel pressure. Long story short, we replaced the fuel line and carb quit flooding. Problem solved. But now we need to fix the water pump. :-(
 
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okgorilla

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Re: 89 mercruiser 3.7 carb flooding

I found rubber chunks in the lower side inlets. The guy I bought it from was starting it without circulating water through the stern drive. (We have an Alpha drive).
 
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stonyloam

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Re: 89 mercruiser 3.7 carb flooding

okgorilla said:
I found rubber chunks in the lower side inlets. The guy I bought it from was starting it without circulating water through the stern drive. (We have an Alpha drive).
Click to expand...

If it did that much damage, your best bet us to replace the whole pump, rather than just the impeller. Also look closely at the old impeller, to see if any large pieces are missing, if so they likely ended up in the exchanger.
 
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okgorilla

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Re: 89 mercruiser 3.7 carb flooding

We replaced the whole water pump and the impeller and checked to make sure there wasn't any pieces in the exchanger. Took the boat out and it was running great. Then it started spewing oil through the carburetor. I am beginning to hate this boat!!
 
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