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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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1997 mercruser 350 chev runs fine minutes starts to run

Customer Question

1997 mercruser 350 chev runs fine for 20 minutes starts to run rough slows down valves start to rattle slows more backfires out carb and shuts off -if I reduce the throttle it doesn't backfire as much and continues to run slow and after a while I can give it a little throttle and it speeds up slowely then after a couple minutes starts all over again-I put -rebuilt carb-new plugs fuel filter -ignition coil -dist cap-rotor button -and the part that goes inside the distributer-I don't know what it is called but where the points use to go on old engines- I am thinking ignition control module -what do you hink
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.
Hello my name is ***** ***** am I speaking with?
Can you be more specific by what you mean/hear or what you think you hear by valves start to rattle? Are you hearing a distinct noise from either valve cover?
Customer: replied 2 years ago.
sounds like valves rattling or knocking or pings
Expert:  Jason replied 2 years ago.
Is the oil level read high on the dipstick by chance?
Customer: replied 2 years ago.
no it is at the full mark
Customer: replied 2 years ago.
the backfiring out the carb has me puzzled
Customer: replied 2 years ago.
think it over I will get back to computer later I have to go for now
Expert:  Jason replied 2 years ago.
Valves rattling would be overfilled oil, so I wanted to rule that out.
The backfiring out of the carb is either a lean fuel condition or the timing is jumping around. Have you tried running it on a fuel tank other than the one in the boat? Do you have a timing light to check timing?
Expert:  Jason replied 2 years ago.
Hello, it looks like you logged off. Did you still need help on this issue?