35hp cough/sneeze

[Rayandrewss]

I just cannot get my 1979 35 hp Evinrude, model 35953A to run smooth. It has a bad "sneeze" that wont go away. I have replaced the following: Stator, coils, plugs & wires, power pack and rebuilt the carburetor. The fuel and lines are new and tight. Link & sync done. As I turn the low idle adjustment, not much happens or it gets worse and quits ( quits if it is adjusted way out, what I think is just too far). Fuel pump works fine. Any ideas would be appreciated as I am way beyond frustrated and running out of cash to put into this motor.

 

[smevil]

Re: 35hp cough/sneeze

I have a 1970, my air fuel mixture screw likes to be turned in all the way then backed out 1 1/2 turns, do you have real good spark on both plugs? Pull both plugs are the wet from fuel or dry from lack of?

 

[jsproline]

Re: 35hp cough/sneeze

sounds like it is running lean. Check air fuel mix screw settings. Carbs could need a good cleaning or kit.

 

[Rayandrewss]

Re: 35hp cough/sneeze

I started at 1 1/2 and went back ( and forward) from there. Plenty of spark on both plugs but they do seem wet....

 

[Johny25]

Re: 35hp cough/sneeze

Are you only having a problem at idle? And how is the tip on your slow speed idle screw, is it worn or grooved at the tip?

 

[bonzoscott]

Re: 35hp cough/sneeze

If all that maintenance has been done correctly, there should be no problem. Does it run smooth at any point (RPM)? Carb cleaning can be a challenge. I have experienced the same problem once I think I have solved. It took soaking the carb in Sea Foam for quite a while (weeks in my case). Other than that, crank seals may be bad. Maybe someone with a better diagnoses will chime in.

 

[Rayandrewss]

Re: 35hp cough/sneeze

JSproline.....the carb was soaked overnight....adjustment screw just doesnt do much
Johny25....screw looks ok...it seems to run better at a higher rpm but, I didnt want to go too high using muffs
Bonzoscott...If the crank seals were bad, would I still have good compression?

 

[Johny25]

Re: 35hp cough/sneeze

Ray do you have the electric choke solenoid on your motor?

 

[smevil]

Re: 35hp cough/sneeze

If you pull the plugs just after it dies and they are wet that means to me it is loading up or flooding.

 

[bonzoscott]

Re: 35hp cough/sneeze

Yes you would still have good compression if the crank seals are bad. But I'm leaning toward "Low Speed Circuit" in the carb now that you say it seems to run better at high RPM. Make sure you check out this:
http://forums.iboats.com/showthread.php?t=244013

 

[Rayandrewss]

Re: 35hp cough/sneeze

Johny25....yes, electric choke....works fine
bonzoscott.......I am leaning toward the crank seals, why? cause it's one more thing I havnt spent money on for this motor. I did the carb cleaning exactly to the link you show. I went thru darn near all the secret files and sticky notes.

 

[Haffiman]

Re: 35hp cough/sneeze

Get the engine in a barrel to get correct back-pressure and proper cooling, start it up.
Check water pump function and that engine reaches proper operating temperature. If thermostat is open, engine will run cold and 'sneeze'.
When adjusting the low speed needle, be sure the carb is completely closed (loosen the roller and keep away from ign cam), and keep the rpm as low as possible by just adjusting the timing advance.

 

[Rayandrewss]

Re: 35hp cough/sneeze

Haffiman....took the thermostat out....it's broke....I will try that next after i order one and keep everyone posted....thank you for your help......Ray

 

[Cofe]

Re: 35hp cough/sneeze

I had a motor doing the same thing as yours awhile back. My problem was either caused by a bad head gasket area between the cylinders, or leaking exhaust baffle gaskets. Anyhow I replaced both, and it started idling correctly.
If you take the head off, make sure the water deflectors are ok while you are there.

 

[Rayandrewss]

Re: 35hp cough/sneeze

Cofe....ordered new therm and gaskets including the head gasket.....I'll keep ya'll posted.....thanks for the help

 

[Rayandrewss]

Re: 35hp cough/sneeze

As I am replacing the head gasket & thermostat.....just wondering if I should do anything else while I am there....tighten the bolts or torque ?

 

[AlTn]

Re: 35hp cough/sneeze

surface the head...I use 180 wet/dry emory cloth ..go much finer and you can wear your arm out...anyway, you'll need to fasten this to a flat surface, I use duct tape, have seen some who use spray on adhesive..and , moving the head with enough hand pressure so it doesn't slip from your grip, use a figure 8 pattern to polish the head checking it for warpage with a straight edge. The surfaces of the head will become one shade when you're getting close < the first laps around the paper you'll notice the high spots are bright and the low ones still dull >. As an alternative you can use valve grinding compound on a flat surface. Saw a vid on youtube of a guy using valve grinding compound on the glass top of a patio table. Gotta think that top is bound to get scratched.

Resist the temptation to use a ziz wheel < abrasive fiber wheel on a die grinder > when cleaning the deck surface of the block as it's near impossible to keep it from dipping the surface. I did this once, and only once, had a water leak to the outside of the head gasket that was thankfully remedied by using a BRP head gasket as it was "softer" in this sealing area.

 

[jerryjerry05]

Re: 35hp cough/sneeze

Take the carb off and inspect the reeds.J

 

[Rayandrewss]

Re: 35hp cough/sneeze

Changed the thermostat, head gasget and other gaskets....no leaks.....still sneezing and blackening the plugs something fierce. Looks like this season of fishing for bass is down the tubes....as was last season shortly after I bought this boat. No more money to spend as I have replaced everything I can think of. In short :.....I give up.
Next thing to do is put the boat on craigs list and take a loss and go back to fishing from the bank......really sucks cause this was my first boat and after a year and a half I have not been able to enjoy it. I am not one to quit as you can see from the first paragraph but it is time to do so. Thank you everyone for your help....on this post and my past posts.....I do really appreciate it........Ray

 

[Haffiman]

Re: 35hp cough/sneeze

Not good news!! However getting closer??
Cough/sneeze is caused by the combustion going down into the crank case. This may only happen if the combustion keeps on as the piston pass the intake ports on its way down.
Normally lean burning (too little fuel) is the reason, but may even be caused by rich mix or low temperature, but may even be caused by faulty ign timing..
Pluggs getting 'Black', indicates a too rich mix.
I've seen a lot of things being changed without results and adjustments been done according to the manual.
But I've seen no 'documentation' in the way of posted pics or posted verification?
If possible, post some pics of your carb synch and set up?
What is the timing (verified by timing light) on BOTH cylinders? (mark up the flywheel for cyl 2 as well)