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Ask K. Kergan Your Own Question
K. Kergan
K. Kergan, Marine Mechanic
Category: Boat
Satisfied Customers: 1031
Experience:  24 yrs exp. Inboard/Outboard mechanic Mercury/ Mercruiser, Volvo Penta and OMC, Johnson/Evin.
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K.Kergan,1985 Mercruiser 3.0 140HP. 1 owner always maintained

Customer Question

Hi K.Kergan,1985 Mercruiser 3.0 140HP. 1 owner always maintained during it's lifetime.Problem goes like this.Cold starts fine, runs like a champ, can tow 2 tubes for hours with no problems.When it is hot outside and the motor is hot (140 degree) and I bring it to an idle and troll for 20-30 minutes it stalls when you attempt to accelerate. Engine will start back up but will stall as soon as you go for forward. After a cool down period of approx. 30-40 min all is fine.Had the carb rebuilt last week and also installed a water sep. yet had the same problem yesterday.The metal fuel line from pump to carb was extremely hot and was thinking that perhaps the fuel is getting to hot?Any suggestions?Thank you.Harry
Submitted: 2 years ago.
Category: Boat
Expert:  K. Kergan replied 2 years ago.
Hi, it sounds like you need to let the choke close before it will start again.This could be a low float level or a problem with the accelerator pump (possibly not set right).If you suspect that the fuel is getting too hot, the boiling point of benzene (gasoline) is 176.18 degrees.If the fuel pipe is getting to that temp, you are definitely getting vapor lock.Suggestions?...look down the throat of the carb and pump the gas, see if the accelerator pump works as it should, it should start squirting as soon as you give it gas.Check the temp of the fuel pipe.Check for an intake leak by spraying wd-40 around the base of the carb, if the sound of the engine changes, you have a leak at the mounting gasket.If these check out, check the float level in the carb.
Customer: replied 2 years ago.
Will check the suggestions.Does any factory replacement fuel line exist that I can replace the metal line with? Or would I have to cut the metal line out and hose clamp new fuel line / re-route away from top of motor?It only happens when motor has been running hard, then idling for 20-30 min and temp under the cover is building up.
Expert:  K. Kergan replied 2 years ago.
It does sound like you're getting vapor-lock.
An infrared temp gauge can give you an exact temp at any specific spot.
Check the temp of the fuel pump too, if you can.
You don't want to hose-clamp fuel lines on the output side of the fuel pump because of the possibility of gas spraying everywhere.
There are flexible fuel lines available for high performance engines if you can find the right one.(right length and end fittings)
Any decent auto parts store should have a selection.
Another possibility is to cover the fuel line with some kind of insulation, you could slit a piece of hose and tie-wrap it in place around the steel line.
Please don't rate this answer until we're done.
Customer: replied 2 years ago.
I am going to pursue replacing the steel line with braided flex w/correct end fittings. Might take me a few days to get it accomplished. Assuming I get it done this week I will know this Sunday if it is the solution. I'll let you know as soon as I do.Thank you for your help.Harry
Expert:  K. Kergan replied 2 years ago.
Sounds good!

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