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Backfire through exhaust

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woodfan

Member
I fogged my 1992 Mariner 75hp last fall. After putting oil in spark plug holes I turned the engine over a couple of times. I just got it out of storage and find the 2cycle oil on the floor of storage unit. Maybe 2-3 oz. Tank was not full when stored.
Started engine today and it is backfiring through the exhaust on anything past idle. Any ideas as to my problem?

Thanks in advance,
Woodfan
 
Where the carburetors empty during storage ??--------------Oil leaking on the floor after fogging is very normal and nothing to worry about.---Have you opened low speed needle 1/4 turn to see if a possible lean condition clears up?? ----are you running with fresh 50:1 for the first tank until you confirm oil injection is working ??
 
I have a built fuel tank, but no to your question on fresh fuel. I do use the blue Stabil rather heavy when I put it up in a garage for the winter. I have used the same procedure for several years. Have never had a problem until now. I do not know how to confirm if the oil injector is working. I assume the carbs did have fuel as I did not run them empty. (I will from now on though).
 
Try fresh fuel from a 5 gallon tank. -------Mix at 50:1 for the first tank.------Mark oil level on the oil tank and after running the 5 gallon tank empty , see how much oil you need to add to get back to the mark.--Motor will smoke a bit more , but you will not damage / destroy the motor.
 
racerone said:
Try fresh fuel from a 5 gallon tank. -------Mix at 50:1 for the first tank.------Mark oil level on the oil tank and after running the 5 gallon tank empty , see how much oil you need to add to get back to the mark.--Motor will smoke a bit more , but you will not damage / destroy the motor.
Click to expand...

Well I tried that and it is still the same. Can an outboard jump timing?
 
The timing on your motor is fixed and does not / can not jump out of time as a rule.----------A sheared flywheel key and loose magnets on the flywheel do throw them out of time.
 
Have you looked at the spark on each cylinder while idling and then compare at WOT w/a timing light? Backfiring can come from cross firing due to plug wires leaking HV. Spray some tapwater on the plugwires when it is idling to see if any wires are leaking HV. Lean carbs will also cause backfing. Have you cleaned and inspected each carb for finite blockages?
 
Gave up and took it in to be repaired. On a two week waiting list but will let you know what happened. I think it did shear the flywheel key, but we shall see.
 
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