Evinrude 70 Stumbling - Strange Symptoms I Haven't Figured Out.

[Sea-Bear]

I just put this Evinrude 70 2-stroke 1984 E70ELCRD on my Arima Sea Chaser a couple weeks ago & I'm still trying to work the bugs out of it. Went through the cooling system, but now we have acceleration issues.

Idles great in the driveway, of course. We get to the dock & she starts up and idles fine. Give it throttle and it takes off and almost gets up on plane & then stalls out. Back the throttle off & she'll do about 10 mph. Floor it again and she takes off, but never do we get sustained power.

Compression 140-140-140
Rebuild fuel pump - check
New hose & primer ball - check
Clean fuel - check
New plugs - check
Inspect pick-up tubes - check
Checked all carb hoses
Choke solenoid lever in correct position

On to test the coils in the driveway. I pulled one plug wire at a time while the engine was running. On the bottom cylinder, there was no change in engine pitch when I pulled the wire. The other two made the engine cough, and almost die. Strong spark jumps over 1/2" nice and white on all bottom cylinders. I even switched the middle and bottom coils with no change. So the ignition system is not suspected at this time. My problem seems to be isolated to the bottom cylinder. I'm thinking the bottom carb needs cleaning.

What puzzles me is how well the engine starts and runs. I'm surprised it has such good power when I first throttle the engine, and it tries readily to jump up on plane. For the first 5 seconds, it takes right off. I'm thinking the bottom carb needs to be taken apart. But the symptoms still have me puzzled. Could it be the float is part way stuck, and the idle jet is clogged, the the high speed jet is clear?

If anyone has an explanation, I'd sure be interested!

 

[wrmdunker]

Re: Evinrude 70 Stumbling - Strange Symptoms I Haven't Figured Out.

Sea-Bear, welcome aboard. Most of the guys like to see the model and year before they reply. Carbs are easy to rebuild and I'm told that a tiny spec of dirt in a jet will give you trouble. I rebuilt all 3 last fall. You can buy the kits here on iboats. Most guys will also tell you to get an OEM manual for the motor. Easy to find on E-bay.

I am having trouble with my 1974 70hp Evinrude and want to troublesoot some ignition items. How did you pull the boot and prevent from shocking yourself? Also, how did you set up to test the spark?

 

[BonairII]

Re: Evinrude 70 Stumbling - Strange Symptoms I Haven't Figured Out.

Make sure your fuel tank vent is open. Run the motor with the gas tank cap completely off if necessary.

 

[Sea-Bear]

Re: Evinrude 70 Stumbling - Strange Symptoms I Haven't Figured Out.

Thank you, wrmdunker. I changed the post, adding the model & year. It's a 1984 E70elcrd. To test spark I have a tool I got from harbor freight. But it doesn't really work that well. So i stuck a bolt into each boot and arched across to the top of its spark plug. If the spark is strong, it will jump 1/2" or more across to the plug & the engine will run just fine. I swapped coils also to see if the problem would migrate with the coil. I did the spark test last to rule out a problem with the power pack. I switched plug wires to rule out problems with them. The problem stayed on the bottom cylinder every time, so it must be the carb.

Thanks, Bonairii. Vents were wide open, and I had my son pumping the primer ball. Good point, because I've had the vent kill my motor a few times when I wasn't thinking!

 

[kentuckydiesel]

Re: Evinrude 70 Stumbling - Strange Symptoms I Haven't Figured Out.

Thank you, wrmdunker. I changed the post, adding the model & year. It's a 1984 E70elcrd. To test spark I have a tool I got from harbor freight. But it doesn't really work that well. So i stuck a bolt into each boot and arched across to the top of its spark plug. If the spark is strong, it will jump 1/2" or more across to the plug & the engine will run just fine. I swapped coils also to see if the problem would migrate with the coil. I did the spark test last to rule out a problem with the power pack. I switched plug wires to rule out problems with them. The problem stayed on the bottom cylinder every time, so it must be the carb.

Thanks, Bonairii. Vents were wide open, and I had my son pumping the primer ball. Good point, because I've had the vent kill my motor a few times when I wasn't thinking!

Sounds like your fuel pump is weak, float needles are sticky or the floats are not adjusted properly. Think about it...the trickle of fuel coming into the bowls on the carbs is fine for idling and even keeps them filled, but when open it up, the fuel flow can't keep up and the engine dies once the fuel that's already in the bowl runs out.

-Phillip

 

[Sea-Bear]

Re: Evinrude 70 Stumbling - Strange Symptoms I Haven't Figured Out.

Thanks KYD. I think you're right it is the float needle valve. I did rebuild the carb & pump the ball while underway. So I guess it's carb cleaning time. Thanks for your help.