1974 mercury 500 4 cyl 50 hp. Idle is not great, and stalls when going into gear in the water. Can get it to run at speed by revving, and even get on plane, but it stalls at lower speeds. I tested the motor by pulling the plug wires off one at a time with the engine running. With either of the lower two spark wires off, the engine speed doesn't change, but with one of the upper wires removed the engine speed drops by half and/or dies. Seems like cyl #3 and #4 aren't firing.
I've replaced things recently, including: engine wiring harness, fuel pump, cleaned carbs to the bowls and replaced lower carb needle valve and gasket. New spark plugs, tested the spark current. Fresh gas, new gas bulb and replaced a couple lines. Compression test is just fine as well. Runs okay in the driveway, but can't get off the launch ramp without dying. What should I do?? Thanks for helping, I'm spent!:facepalm:
I've replaced things recently, including: engine wiring harness, fuel pump, cleaned carbs to the bowls and replaced lower carb needle valve and gasket. New spark plugs, tested the spark current. Fresh gas, new gas bulb and replaced a couple lines. Compression test is just fine as well. Runs okay in the driveway, but can't get off the launch ramp without dying. What should I do?? Thanks for helping, I'm spent!:facepalm: