Hello,
I'm running out of ideas on this one. Hoping someone has some insight to share...
1986 evinrude 40hp 2stroke outboard
I will leave the dock in the morning and give full throttle. The motor does as expected and gives me full rpm, full power... but for only about 30 seconds. After which the power surges in and out as the motor power drops down to a consistent low. My 18' alumnacraft usually tops out at 40mph. The low power condition will have me puttering along at 10-15 mph. I get to my fishing spot and fish for an hour or two before moving. Again, for 30 seconds I get full power and then the motor tapers off to a low power for the remainder of my trip.
- Checked compression - both cylinders at 120psi.
- idles just fine. No issues here.
- Under no-load (neutral) the engine will run full rpm without issue.
- Under low load, low speed, all seems fine.
- I replaced the fuel line and primer bulb from the tank to the motor. No change.
- I tried just cutting the fitting off the end of the line and sticking it directly into the tank. No change.
- I replaced the fuel pump and the fuel lines going from the input to the carbs. No change.
- tried uncapping the fuel tank to vent in case it was not venting properly. No change.
- I took the carbs off and soaked them in carb cleaner and picked the orifices clean with a wire orifice pick. Blew compressed air through the passages, etc. This seemed to steady the power out (no longer bogs out or sputters as it did months ago when the problem began) but still experiencing low power when wanting full throttle under load.
- I visually observed the spark plugs firing, but never replaced any plugs or wires.
Notable test:
after puttering across the lake at low power I shut the motor off and disconnected the fuel lines immediately to check to see if the carbs bowls were full - yes, fuel was in both of them.
I'd be very appreciative if anyone has any ideas or suggestions here. This one is stumping me.
Thank you!
Tim
I'm running out of ideas on this one. Hoping someone has some insight to share...
1986 evinrude 40hp 2stroke outboard
I will leave the dock in the morning and give full throttle. The motor does as expected and gives me full rpm, full power... but for only about 30 seconds. After which the power surges in and out as the motor power drops down to a consistent low. My 18' alumnacraft usually tops out at 40mph. The low power condition will have me puttering along at 10-15 mph. I get to my fishing spot and fish for an hour or two before moving. Again, for 30 seconds I get full power and then the motor tapers off to a low power for the remainder of my trip.
- Checked compression - both cylinders at 120psi.
- idles just fine. No issues here.
- Under no-load (neutral) the engine will run full rpm without issue.
- Under low load, low speed, all seems fine.
- I replaced the fuel line and primer bulb from the tank to the motor. No change.
- I tried just cutting the fitting off the end of the line and sticking it directly into the tank. No change.
- I replaced the fuel pump and the fuel lines going from the input to the carbs. No change.
- tried uncapping the fuel tank to vent in case it was not venting properly. No change.
- I took the carbs off and soaked them in carb cleaner and picked the orifices clean with a wire orifice pick. Blew compressed air through the passages, etc. This seemed to steady the power out (no longer bogs out or sputters as it did months ago when the problem began) but still experiencing low power when wanting full throttle under load.
- I visually observed the spark plugs firing, but never replaced any plugs or wires.
Notable test:
after puttering across the lake at low power I shut the motor off and disconnected the fuel lines immediately to check to see if the carbs bowls were full - yes, fuel was in both of them.
I'd be very appreciative if anyone has any ideas or suggestions here. This one is stumping me.
Thank you!
Tim
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