89 Evinrude 70hp inconsistent

[joho5]

89 Evinrude 70hp. The VRO has been disabled, and I just use a standard fuel pump.

Now when I had it out today, it was surging real bad and wouldnt maintain consistency at wide open throttle. I was inspecting the obvious things and noticed that my primer bulb was flat, so I just figured one of the valves in the bulb were bad. I ran up to the house and grabbed another bulb, it didnt go flat, but still wouldnt act consistent at WOT, and would die here and there.

This is exactly how it was doing to me earlier this year in the summer and I rebuilt the fuel pump, and it fixed it instantly.

I noticed last trip that the primer bulb was taking a little long when I would prime the motor, to fill back with air each time i squeezed it.

so my dad backed down to load it back up today, I was by myself and I gunned it and it jumped out and ran fine for about 300 yards so I stopped, I turned around and gunned it back and it acted fine.

so I dont know...its inconsistently inconsistent...ha

any thoughts on what to check.

 

[joho5]

Re: 89 Evinrude 70hp inconsistent

forgot to mention that the times when I was having trouble with it dying, I could keep it going with the primer / choke knob on my controls.

 

[joho5]

Re: 89 Evinrude 70hp inconsistent

Would it be a possibility to have the tank over full? This is the first time I have ever filled it up all the way up to the fuel fill valve, like where it came running out a little before I stopped. (my fuel guage stopped working and I didnt know how much gas was in it is why)

then when the boat tilts back when trying to get on plane, the gas tilts back as well, and then the vent hole plugs up with gas entering it and causes the air problem?

I was just thinking, and came up with that theory...

 

[kenmyfam]

Re: 89 Evinrude 70hp inconsistent

Siphon a little out of the tank and see.
Tank must be vented or you will get the flat bulb thing.
If still bad do a basic health check.
Compression
Spark
Fuel delivery
Spark plug condition.
Beyond that clean the carb's

Let us all know.

 

[joho5]

Re: 89 Evinrude 70hp inconsistent

how do you do a fuel delivery check...if the bulb was going flat, that indicates that fuel wasnt going to the motor right? because the motor is pulling a vaccum trying to pull fuel, but the bulb was keeping it from doing that for whatever reason and just going flat instead of letting fuel flow through?

 

[kenmyfam]

Re: 89 Evinrude 70hp inconsistent

Is the tank vented ??? First thing i asked I think.

 

[joho5]

Re: 89 Evinrude 70hp inconsistent

yes, there is a vent...its a tube about 6" that vents out the back.

 

[kenmyfam]

Re: 89 Evinrude 70hp inconsistent

So is the vent actually venting ???? or is there a kink or blockage ???

 

[MellowYellow711]

Re: 89 Evinrude 70hp inconsistent

Take your gas cap off and run for a little while. If this fixes the issue, you have venting problems. If that doesn't work, look to the anti-siphon valve or water/fuel seperator.