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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10701
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I've got a 1990 mercruiser with a gm 5.7 and quadrajet carb.

Customer Question

I've got a 1990 mercruiser with a gm 5.7 and quadrajet carb. Stops running and appears the bowl runs dry at 140f on the temp gauge. Just rebuilt the carb and same problem. Has enough fuel pressure at the carb to spray out when the fuel line is cracked open. Baffled.
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.
Hello. My name is ***** ***** I will be assisting you today.
Pull the fuel filter out of the carb inlet fitting is it in backwards?
Customer: replied 1 year ago.
Already removed it entirely after we changed the big filter and had pressure at the fuel line. I got it to run since I wrote, but not 100%. After checking and adjusting the float up a bit it would stay running if I pumped the throttle. After doing that 10-15 times it smoothed out a bit and would stay running. Took it for a few laps of the lake and it got progressively better. At first did not want to run anywhere near WOT but pumping the throttle I was able to coax it up to WOT eventually. Now it runs a little rough but will run up to WOT without pumping.
Expert:  Tan replied 1 year ago.
What do you have the idle jets adjusted at?
Customer: replied 1 year ago.
Not exactly sure, left them where they were. How would I determine the answer your looking for?
Expert:  Tan replied 1 year ago.
The jets are in the base of the carb towards the front there are 2 jets. Turn the jets in till they lightly seat. Now turn them CCW 1.5 turns out. Now start the engine run it at idle. Now you can adjust these 2 jets to achieve the best idle. In to give it less fuel and out to give it more fuel.
Customer: replied 1 year ago.
Ok, we have left the property for the next week or two. I will see what happens next time we are there. I still dont understand the apparent temperature dependence. We probably repeated the 140F stall 5-6 times repeatably. Seeing it clear out today seems like maybe some fuel quality issue, but prior the engine would start no problem and run smooth as silk until 140F.
Expert:  Tan replied 1 year ago.
The engine temperature won't have an affect on the running of the engine. But you could have an ignition coil breaking down due to heat. The coil can get hot and start breaking down. The way to see this is with a timing light. Connect the light to one of the plug wires see if the spark becomes sporadic. If it does replace the coil. Post back with findings and questions.

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