70 H.P. Evinrude Motor surging

[Tinkerbell]

Have a 1989 70 HP Evinrude 3 cylinder, it idles good, runs at fast speed good, but between idle and fast speed, I get a severe surging of the motor, speed up, slow down, speed up, slow down. Could some one give me some advice. I have fresh gas, a new gas line. What could be wrong in my carbs to create such a situation?

Thank you for any advice

 

[Daviet]

Re: 70 H.P. Evinrude Motor surging

There is an early and late production carb for your engine, do you have an adjustable low speed adjustment on your carb? By the way you describe the problem I would think you have a fuel delivery problem. You need to check the fuel pump operation, you can try pumping the primer bulb when it is happening and see if it helps. If that doesn't help, it might be time to overhaul the carbs. It might be a good idea to check the spark and compression also as part of your troubleshooting.

 

[Tinkerbell]

Re: 70 H.P. Evinrude Motor surging

There is an early and late production carb for your engine, do you have an adjustable low speed adjustment on your carb? By the way you describe the problem I would think you have a fuel delivery problem. You need to check the fuel pump operation, you can try pumping the primer bulb when it is happening and see if it helps. If that doesn't help, it might be time to overhaul the carbs. It might be a good idea to check the spark and compression also as part of your troubleshooting.

I have been reading lot's of post concerning the VRO system. My motor originally came with the VRO system, it has been taken off and I now mix my fuel. Does the fuel pump have to be changed after the VRO has been disconnected? If so, why? What would be the symptoms of running the same fuel pump.

 

[Tinkerbell]

Re: 70 H.P. Evinrude Motor surging

Don't think I have a low speed adjustment, I might add to my orginial post, my motor has only been ran maybe three times in the past 18 month, would you think my carbs may be gummed up?

 

[Daviet]

Re: 70 H.P. Evinrude Motor surging

You can use the fuel pump side of the VRO pump without a problem as long as it is working properly. If the engine and fuel system was not prepped for storage properly you could have some problems with the carbs.