Motor sneezing

[Jggrmson]

What causes a motor to sneeze and die. I have heard it is a lean condition but how do I fix it? Iv played with the low speed adjustment screw and can't get it to stop doing it. Only happens at idle or low speeds.

Compressions good
Carb was recently cleaned and rebuilt
Fuel pump recently cleaned and rebuilt
Runs really well when cruisen but won't stay running long at idle.

Oh...it's a 35 hp Evinrude from 1977. Model number 35702c

Thanks

 

[flintcreek]

Re: Motor sneezing

Good luck I have a 77 model Johnson 35 hp that will just crank run for a few seconds and go dead. I have not had it on the water to try to open it up and see if it will run out on top end. So far I have not had any luck....like you good compression and changed out pretty much everything else....but still running out of fuel. The starting point for the low speed jet is 1.5 turns out after gently bottoming the screw out. When the carb was rebuilt did you take the knock (aluminum plugs) outs out and make sure the low speed was clean. If not that is where I would start. Sounds like the low speed circuit in your carb is still not clean.

Flintcreek

 

[Cofe]

Re: Motor sneezing

Temporarily put something like plumbers putty, or chewed chewing gum around the slow speed needle valve. You may have air in leakage there.

When the carb was rebuilt, were the core plugs pulled, and the slow speed idle circuit under the top core plug cleaned?

 

[boobie]

Re: Motor sneezing

Have you given this mtr a good de-carb lately? You could have some stuck lower rings.

 

[Jggrmson]

Re: Motor sneezing

Temporarily put something like plumbers putty, or chewed chewing gum around the slow speed needle valve. You may have air in leakage there.

When the carb was rebuilt, were the core plugs pulled, and the slow speed idle circuit under the top core plug cleaned?

I did knock out all the caps, soak and hit everything with compressed air. I'll try the gum thing when it stops raining its *** off

Thanks

 

[Jggrmson]

Re: Motor sneezing

Decarbed last season on the muffs

So is it a carb issue? I had some trouble trying to remove the high speed jet when I cleaned it last season, so I just left it in there. I an sure it had no blockage though.

 

[kbait]

Re: Motor sneezing

Low speed carb blockage or leaking low speed needle retainer (plastic o-ring looking deal that seals the low speed adjustment needle would be my first guess. Did you replace the 5/32 fuel line from pump to carb? If it's original and had ethanol fuel run through it, it may be sloughing off inside and gumming your carb, as there's no screen past the pump to stop it. I cleaned/rebuilt a 25 carb a couple years ago, and it immediately gunked up the low speed circuit when I test ran. I ALWAYS replace that hose now when I work on 'em.. got a whole spool!

 

[bktheking]

Re: Motor sneezing

Crank seals tip top on that motor?

 

[Jggrmson]

Re: Motor sneezing

Crank seals tip top on that motor?

Embarrassingly...i have no idea what that means

how do i check?

 

[Jggrmson]

Re: Motor sneezing

Low speed carb blockage or leaking low speed needle retainer (plastic o-ring looking deal that seals the low speed adjustment needle would be my first guess. Did you replace the 5/32 fuel line from pump to carb? If it's original and had ethanol fuel run through it, it may be sloughing off inside and gumming your carb, as there's no screen past the pump to stop it. I cleaned/rebuilt a 25 carb a couple years ago, and it immediately gunked up the low speed circuit when I test ran. I ALWAYS replace that hose now when I work on 'em.. got a whole spool!

i didn't, but it has been replaced. i took it off and inspected it...looks new on the outside and i wrapped a paper towel on a screwdriver and pushed it all the way threw...came out clean.

 

[ONERCBOATER]

Re: Motor sneezing

if the carb and fuel system proves good, then air could be leaking from upper crank seal...causing a lean condition...I would hazard a guess that the gasket behind the carb could also cause this if not replaced when carb removed for cleaning, pretty much if fuel pump and carb are good and you have no leaks up to carb then I would be looking for air leaks after the carb and on the case and seals.

Sean