Lean Sneeze

[Auxlarry]

I got the engine back together and it sounds great and runs good except once I put it in the water it appears I have a slight lean sneeze at idle. Didn't run it past 1500 rpm and just cruised (putted) around the lake for over an hour.

If a lean condition do I retard or advance the timing?

Thanks,
Larry

 

[emdsapmgr]

Re: Lean Sneeze

This is not a timing or ignition problem. A lean sneeze relates to the fuel mixture-"lean". A common problem on carbs that have not been completely torn down and cleaned internally in some time. When the engine is at idle, the carb butterflys are completely closed. The fuel goes thru special idle passages. If these passages get restricted with dried fuel (common over long periods of time) you will get the sneeze effect. You'll need to tear the carbs down and insure that these idle passages are cleaned with something which will dissolve dried fuel-like a gumout type product. Running carb cleaner thru the fuel system won't do it.

 

[Auxlarry]

Re: Lean Sneeze

emdsapmgr,
The carb rebuild was included with my complete powerhead rebuild. The carbs were completely stripped including removing the plugs, soaked in gumout carb cleaner and I made sure the jets were cleaned with a wire through each. Looked great at reassembly with all new parts but I can pull them and check again.
I may want to purchase a new tach because using the boat tach the idle seems low to me when in gear even though it says 700rpm. I assume a low idle speed could cause this same issue with a sneeze?

Thanks,

Larry

 

[SparkieBoat]

Re: Lean Sneeze

emd is correct, my guess would be idle passage clog also. you should remove the carb cover and put your hand over the carbs and check for even suction and no blow back.

 

[Auxlarry]

Re: Lean Sneeze

Sparkie,

I did this yesterday on the muffs and the suction on the carbs feels good. I will pull the carbs and double check them.

Thanks,
Larry

 

[emdsapmgr]

Re: Lean Sneeze

The engine should still idle ok at a low rpm if the idle passages are open. Not unusual for tachs to be off somewhat-unless it is a digital tach. The analog ones can be off a little at various points throughout the whole rpm spectrum, including at idle rpm's. You could try to advance the idle a hundred rpm or so to see what happens, keeping in mind a low idle is optimal for shifting the clutch dog into/out of gear.

 

[keefallan]

Re: Lean Sneeze

You did not mention if the reeds were replaced with composites like Boyesons or the like. My motor sneezed till I rejetted the idle jets. Also, the idle ciruit is not used higher up in the rpm's. I ran mine all day long that day cause I knew that nothing would happen to the motor cruising on a plane. The throttle blades are open and air is running thru that circuit and not the idle passages.

 

[James R]

Re: Lean Sneeze

Have always used, for many years, Gunk Carb and Parts cleaner and soaked the stripped carbs. No danger of damaging plastic parts with this product and it breaks down the grunge or shelac if you prefer.

 

[Auxlarry]

Re: Lean Sneeze

keefallan,
I replaced the reeds with stock BRP reeds. I am not trying to make a race boat just a good running stock motor. It looks like the best place to start is pulling the carbs off and going throung them again.

 

[boobie]

Re: Lean Sneeze

Auxlarry, I've never used a tach to set idle speed. When it shifts in and out of gear easy and won't stall, that's the correct idle speed.

 

[wyngo]

Re: Lean Sneeze

check all the little hoses around the carbs for leaks, and check the bolts on the manifold for the correct torque.

 

[SparkieBoat]

Re: Lean Sneeze

if this persist after a second carb soaking, I would start thinking that you may have a crank case pressure loss issue. a full speed run will tell if you have that type of issue. the engine will be weak and boggy. also I think you should be running double oil for a while. Aslo it may help to know what motor year and HP and model you are talking about.

 

[Auxlarry]

Re: Lean Sneeze

boobie,
I have always felt the same way. In the past the tach always hovered around 900rpm with the leg in the water in neutral and I noticed the other day it was around 700rpm in neutral and I forgot a screwdriver...lol. I'll pull the carbs and clean/inspect them again just for GP's and see how that does.
Thanks for the suggestion!
Larry

 

[Auxlarry]

Re: Lean Sneeze

wyngo,
I replaced all the recirc lines when I reinstalled the intake manifold. Those should not be an issue but I will check them when I pull the carbs.
Thanks,
Larry

 

[Auxlarry]

Re: Lean Sneeze

Sparkieboat,
The engine is a '83 115hp evinrude, off the top of my head I cant remember the model.
I would hope this is not a problem! The crankcases surfaces were spotless and I used a good anerobic gasket maker and the case slid straight down on the taper pins as I installed it. No movement at all between them at assemble and all the bolts got torqued down per spec.
Since I haven't run the rpms up yet I'm not sure if I will have a weak or boggy situation. I guess I'll find out when I get it broke in and can feel comfortable getting it up on plane and enjoying it. I am running premix at 25:1 and will probably do that for a couple of tanks of gas until I feel comfortable with the rebuild.

Thanks for your help!
Larry

 

[SparkieBoat]

Re: Lean Sneeze

I have a 1984 110 HP Evinrude, it is a great motor. I actually remember now that I still get a slight lean sneeze when I start it. It has been like that ever since I have owned it. maybe idle jets need to be enlarged slightly. But I have just learned to live with it. motor runs out great. maybe it was something with those models.

 

[Auxlarry]

Re: Lean Sneeze

I have been very happy with the 115 hp crossflows I have had over the years. This is the third rebuilt powerhead (first one I have rebuilt) that has been on this boat in the 21 years I have owned it. I usually get a couple thousand hours on them before they start getting tired and I run them hard in their lives.
I'm hoping my rebuild is as good as any I have purchased in the past.

Larry

 

[Auxlarry]

Re: Lean Sneeze

UPDATE
Well, I removed the carbs this morning and tore them down, cleaned them all pretty again and reinstalled them on my newly rebuilt power head. Started it up and my idle was very high, adjusted the idle to 800rpm with the motor on the muffs and it purrs like a kitten.
Readjusted the idle to around 1100rpm and took it to the lake. Started it in the water and my idle is steady at 800rpm and it shifts and runs wonderful.
Not sure what I did different but it did make a difference.

Thanks for all the help and suggestions to all! This site and the folks on it have never let me down and are avery friendly bunch!

Larry

 

[SparkieBoat]

Re: Lean Sneeze

you had a clogged idle jet.

 

[Auxlarry]

Re: Lean Sneeze

Must have Sparkie, but everything looked good! Oh well, live and learn!
Thanks for your help!
Larry