Logo

Mercruiser 4.3 lx 1983 thunderbolt lV ignition looses power above 3400rpm

Stanwaldruff

New member
Checked fuel line/fuel filter/ anti-siphon valve/ rebuilt 4 barrel carb/ replaced distributor cap/ rotor/ ignition sensor/coil...starts easily runs strong up to 4600rpm..25 seconds it looses power -about 1200 rpm and surges a couple hundred rpms.. so could it be my ignition module going bad? How do you test it - new one about 600$. I gong to recheck my floats on the rebuilt carburetor. NO back firings just lose power at high end.
 
If it were the timing control module I would suspect you would not get above say 2400-2600 rpm. That is what that module does, advance the timing.
So I agree, A fuel related issue, pressure, vent clogged, tank pick up clogged, carb filter clogged or carb needs rebuild.
 
Back
Top