1985 Evinrude 70 surging at WOT

[Tumbleweeds]

We recently bought this used motor which ran fine for about a week, then started acting up. At WOT, or even close to it the motor loses power, then surges ahead, loses power, surges etc. It runs great at lower speeds, if a bit rough at idle. I have no tach or useful instruments, so don't know where exactly this occurs. Carb related? I'm new to boats/motors.

 

[clanton]

Re: 1985 Evinrude 70 surging at WOT

Pump the primer bulb when surging,if surging clear up, check fuel system.

 

[Tumbleweeds]

Re: 1985 Evinrude 70 surging at WOT

Thanks Clanton, I'll try that tomorrow when I go looking for Pike on the Mississippi!

 

[Tumbleweeds]

Re: 1985 Evinrude 70 surging at WOT

While surging we pumped the primer bulb and it killed the motor. Re-start was no problem. We also put in new fuel tank, fuel line and bulb, and fuel filter. No good. Shop suspects needle valves? Does this motor have needle valves? Can high/low speed orifice plugs act up like this? Will re-building carbs help?

 

[petryshyn]

Re: 1985 Evinrude 70 surging at WOT

If it got worse with added primer, it appears to be rich. I'd go through the carbs and pay close attention to the floats and needle/seats as recommended.....