Hi guys,
I have a 1974 Evinrude 70HP (3cyl) 2 stroke on my pontoon. The motor does and always has ran wonderfully at idle and at low ranges, but in the higher throttle ranges, the unit will run strong for about a minute, then lose power, then have power surges that decrease in strength and longevity until the unit is running smoothly, but at extremely decreased RPM. If the primer bulb is pumped furiously, the engine will slowly pick back up and run fine. This is with fresh fuel and new plugs. I also have a large amount of oil discharge from the exhaust after being on the lake (about 1/8 to 1/4 cup, it slowly drips out after I drop the engine from the transport position. It is 2 cycle oil and not lower unit dope. I know some discharge is normal, not sure if that amount is.) I have had the carbs cleaned, rebuilt and tuned, replaced every inch of fuel line from the carbs to the tank, replaced the tank and rebuilt the fuel pump. The plugs all produce strong spark, the compression is excellent on all 3 cylinders. I don't know what to try now... Help.
I have a 1974 Evinrude 70HP (3cyl) 2 stroke on my pontoon. The motor does and always has ran wonderfully at idle and at low ranges, but in the higher throttle ranges, the unit will run strong for about a minute, then lose power, then have power surges that decrease in strength and longevity until the unit is running smoothly, but at extremely decreased RPM. If the primer bulb is pumped furiously, the engine will slowly pick back up and run fine. This is with fresh fuel and new plugs. I also have a large amount of oil discharge from the exhaust after being on the lake (about 1/8 to 1/4 cup, it slowly drips out after I drop the engine from the transport position. It is 2 cycle oil and not lower unit dope. I know some discharge is normal, not sure if that amount is.) I have had the carbs cleaned, rebuilt and tuned, replaced every inch of fuel line from the carbs to the tank, replaced the tank and rebuilt the fuel pump. The plugs all produce strong spark, the compression is excellent on all 3 cylinders. I don't know what to try now... Help.