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I have a 2010 Mercruiser 3.0 LX (Actually a GM longblock).

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I have a 2010 Mercruiser...
I have a 2010 Mercruiser 3.0 LX (Actually a GM longblock) . It was running fine when it winterized, but during preseason check now, the engine will not idle.
When the throttle is moved below 1200 RPM it immediately stops. To diagnose I have done the following:
- Swicth Carb with a spare carb. Tis cab was tested last summer, an no idle issues with it. Basically the two carbs give the same symptom
- Cleaned gasoline filter /Water separator again, and connected a fuelline from spare can with fresh fuel, ruling out old mocked fuel. I did let it run for 15 min before I tried to go below 1200 RPM. Fuel from fuel filter did not look that clean, so the fuel in the tank looked contaminated, but since I used fresh gas from separate spare can, it could rule out
contaminated fuel.
- When the engine stalls, it is hard to start, only starts if I poor some fresh gas directly into the venturi.
The engine got electronic ignition from GM installed at same time as longblock, worked well when winterized.
Submitted: 2 months ago.Category: Boat
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Answered in 1 minute by:
5/27/2018
Marine Mechanic: Jason, Marine Mechanic replied 2 months ago
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 18,211
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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Hello my name is ***** ***** am I speaking with? I read what you wrote. Have you checked compression, spark output, and timing yet?

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Customer reply replied 2 months ago
Hi, Thanks for your response. My name is ***** ***** I am the owner of the engine/boat. The engine has been idling without any issues when winterized, and as a part of the winterizing I always fogg the engine, on low RPM, and it shuts gracefully down. Sine then the engine has not been used so I do not think compression or timing (No timing belt, nad noe camshaft repair has been undertaken, so timing shold not change.) Ignition timing not touched since last
autum. When running on 1200 or above, it runs nice no hesitation.
Marine Mechanic: Jason, Marine Mechanic replied 2 months ago

Hi Inge, I'm not talking about the cam timing, which is what a timing belt is for. I am talking about the ignition timing. That being said. The engine needs 3 things to run. Compression, timed spark ignition, and the proper ratio of fuel to air. If you do not think the compression or ignition timing is the problem, then what are you thinking? What do you think the problem is?

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Customer reply replied 2 months ago
I am thinking in the direction of the fuelpump which follows the rev of the engine, but there is no fuel in the clear plastic line between the pump and the carb. Since it worked before it was winterized, there is not major reason why ignition timing should change, it seems more that something has been damaged by the long stand still or low temp or humidity during the winter storage
Marine Mechanic: Jason, Marine Mechanic replied 2 months ago

Well, the carburetors float bowl does hold enough fuel for roughly 30+ seconds of engine operation, so if the pump was the problem, you would still be able to throttle up and the engine will usually run fine for that 30+ seconds and then stall out from lack of fuel. But if you thinking the pump is bad, hook up a fuel pressure gauge between the pump and carb and check the pressure. It should be at least 3 PSi at all times. Let me know how you make out.

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Customer reply replied 2 months ago
OK thanks I will test that.
Marine Mechanic: Jason, Marine Mechanic replied 2 months ago

you are very welcome. Keep me posted.

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Marine Mechanic: Jason, Marine Mechanic replied 2 months ago

Hello, just checking in. Any progress?

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