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Evinrude 20 (25) HP 1983 wont idle when starting cold

C

calle

Member
Hi

I have searched the forum without finding help regarding this specific model so I post the question here.

Im pretty sure my motor is a derated 25 hp meant for the european market (I live in Sweden). Its a rope start with ordinary choke (no primer, a throttle/plate that closes the air intake)

The problem is when starting it cold. It fires on the third pull at the latest but it wont idle, it dies after a few seconds. I have to quickly put in gear to be able to give it more gas, and that solves it, but Im not satisfied with that because its not always convenent to be forced to leave the bridge immediatly after start. My starting sequence is as below:

1. Pumping the fuel bulb until "hard" (I see fuel leaving the fuel filter through transparent fuel hose).
2. Apply full choke
3. Turn gas as much as possible (i guess its start mode, the markings are all gone)
4. Pull rope

After failed start I have tried both full, half and no choke, full choke seems to give the best result but it still dies after a few seconds.

What I have done when troubleshooting:
1. Adjusting the low speed fuel-air mix needle starting from 1 turn from the leanest up to 3 turns from leanest (least fuel) with no effect on starting. When hot, I have found the best setting to be 1 turn from leanest mix.
2. Checked the choke throttle - works fine - when pulling the choke out the throttle closes the intake completely.

If I quickly put in a gear, I only need to rev it slightly above the neutral gashandle limit in order to get it running. It wont take long before I can go back to neutral and the engine runs fine on start gas position and soon on idle aswell.
I bought it a few months ago, the seller said he cleaned the carb and changed fuel filter. Considering the smooth run when warm, Im not so sure its a fuel issue.

Any help would be much appreciated.
Thanks, Carl
 
It might be a leaking top crankshaft seal. This would require pulling the flywheel off to check. Once you do that you can pour a few drops of light engine oil on the seal lip. Slowly rotate the crankshaft (plugs out) and if the oil bubbles air around the seal, you will need to replace that part.

Other than that I am at a loss. Maybe someone else can give you some tips also.
 
What you describe is just about normal (including my own motor). After it starts, and wants to sneeze and stall a quick pull and release of the choke knob should keep it running. Repeat as normal until it warms up enough to stay running on it's own.

One thing you might want to check is make sure the carburetor throttle is starting to open at the mark on the cam.
 
There is an adjustment on the starbd side of carb, right on the throttle shaft. Maybe somebody tweaked it and your carb butterfly is not opening enough for adequate warm up speed which of course is strictly limited these days. Right......these rarely produce a leaky crank seal. Symptoms are not quite right for that anyway. At WOT the carb butterfly should be ever so slightly closed from horizontal when motor is level. This may help guide you if adjustment at throttle shaft has been fouled up. These are excellent motors, I really love 'em. Troll right down to nothing when properly tuned. I run mine at 100 to 1 on only Amsoil with non oxy. Have not had a single failure in 35 years, running resorts in remote Ontario Canada. Some motors with 4000 hours running time, still compression at 125 psi. I HAVE to tell the truth, I got a bad memory!
 
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Thanks everyone for good advice! After I posted I did some adjustments again to the low speed mix screw, i found that on my motor the best setting seems to be about 80 % of 1 turn from leanest mix both on idle and a 1/6 or so of WOT. The day after I went to start it, started on second pull and then I quickly un-choked it anf then it ran good on idle. Same thing today using the same procedure. So I guess I fed it to much gas. It was a combination of your input that fot me to do it. Thanks alot!
 
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