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25 hp mercury intermittent bogging at full throttle

K

KRF

New member
My 1990 low hour Mercury 25 has always run great. Have never run gas more than 3 weeks old.last year on a fishing trip, ran great on first 4 gallons of fuel. When I changed tanks, fuel from marina, while running full throttle, engine would bog down, repeatedly. Changed back to first tank, ran great rest of trip.

This year, ran great for 4 gallons, got 2 gallons at a different marina, started bogging down again. Pumped fuel bulb repeatedly 6-8 times, while engine idled. Engine ran great for a day and started bogging down again.

Any thoughts?
 
Vent is clear on both tanks. Bogging occurred with both tanks. First time, switching back to newer tank with 1-2 gallons left in tank, motor ran fine. Second time ran about 5 gallons. Removed tank and added 2 gallons. Ran about a gallon before bogging started.
 
Fuel filter about a third full, pumped bulb, filter went to 3/4 full, then drained back to 1/3. With motor idling pumped bulb again. Filter stayed 2/3’s full. Motor ran great till next day.
 
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