Hi folks,
I have a 1976 70 HP Evinrude that has been in storage for 17 years that I'm hoping to get some advice on in troubleshooting.
What it's doing:
Using the choke on a cold start the motor starts quickly and after a brief warm up (less than a minute) at a fast idle it will idle down smoothly. The motor runs well at most speeds and I get 5400 RPM at 33 MPH at wide open throttle. The motor idles at 1050 RPM in neutral, and about 785 in gear. The problem is what seems to be a lean bog as I advance the throttle past low speeds to get the boat on plane. It starts to hesitate at about 1800 RPM and struggles until past 3000 RPM, then responds well. I say a "lean" bog because if I just quickly blip the choke when it's hesitating it'll pick right up and take off, which indicates to me it's lean for fuel at those speeds. Pumping the primer bulb has no effect on how the engine runs.
What I've done to date:
After removal from storage I replaced the water pump, all of the fuel lines, and the spark plugs. I purchased a kit and rebuilt the fuel pump. I purchased carburetor kits and took the carbs apart. They were remarkably clean inside, and only the lower carb had some varnish deposits in the bottom around the high speed orfice. Regardless, I removed the high and low speed orfices from all the carbs and cleaned them, used jet spray carb cleaner and compressed air through all of the passages, and gently ran a fine wire chase through the nozzels and through the 3 small idle ports in the carb casting near the throttle plates to makes sure they were not blocked, which they weren't. I put in all new gaskets and washers, new floats, and new needles and seats. I made sure the float levels were set so that when inverted the floats were parallel with the surface of the carb. The reeds in the reed cages looked like new and I put everything back together. I do have the factory service manual and I checked the link and synch as detailed and it appears to be spot on without me having to adjust anything. I also checked the timing plate under the flywheel and it moves smoothly and freely as the throttle is advanced. I also, of course, put fresh oil in the gearcase and lubed all the lube points. Also, compression for the 3 cylinders measures 140, 138, 138. All of the above work was done before I started the motor for the first time.
Do you have any ideas as to what may still be causing this hesitation as the throttle is advanced? I am thinking of pulling the carbs again and setting the floats a little higher to slightly raise the fuel level in the bowls, but am otherwise a bit stumped as to why it goes lean in the low midrange. Any and all ideas and questions are welcome! Thanks very much!
I have a 1976 70 HP Evinrude that has been in storage for 17 years that I'm hoping to get some advice on in troubleshooting.
What it's doing:
Using the choke on a cold start the motor starts quickly and after a brief warm up (less than a minute) at a fast idle it will idle down smoothly. The motor runs well at most speeds and I get 5400 RPM at 33 MPH at wide open throttle. The motor idles at 1050 RPM in neutral, and about 785 in gear. The problem is what seems to be a lean bog as I advance the throttle past low speeds to get the boat on plane. It starts to hesitate at about 1800 RPM and struggles until past 3000 RPM, then responds well. I say a "lean" bog because if I just quickly blip the choke when it's hesitating it'll pick right up and take off, which indicates to me it's lean for fuel at those speeds. Pumping the primer bulb has no effect on how the engine runs.
What I've done to date:
After removal from storage I replaced the water pump, all of the fuel lines, and the spark plugs. I purchased a kit and rebuilt the fuel pump. I purchased carburetor kits and took the carbs apart. They were remarkably clean inside, and only the lower carb had some varnish deposits in the bottom around the high speed orfice. Regardless, I removed the high and low speed orfices from all the carbs and cleaned them, used jet spray carb cleaner and compressed air through all of the passages, and gently ran a fine wire chase through the nozzels and through the 3 small idle ports in the carb casting near the throttle plates to makes sure they were not blocked, which they weren't. I put in all new gaskets and washers, new floats, and new needles and seats. I made sure the float levels were set so that when inverted the floats were parallel with the surface of the carb. The reeds in the reed cages looked like new and I put everything back together. I do have the factory service manual and I checked the link and synch as detailed and it appears to be spot on without me having to adjust anything. I also checked the timing plate under the flywheel and it moves smoothly and freely as the throttle is advanced. I also, of course, put fresh oil in the gearcase and lubed all the lube points. Also, compression for the 3 cylinders measures 140, 138, 138. All of the above work was done before I started the motor for the first time.
Do you have any ideas as to what may still be causing this hesitation as the throttle is advanced? I am thinking of pulling the carbs again and setting the floats a little higher to slightly raise the fuel level in the bowls, but am otherwise a bit stumped as to why it goes lean in the low midrange. Any and all ideas and questions are welcome! Thanks very much!
