Idle and low throttle problems...

[GreenF350]

First off this is on a 1991 40hp motor (E40ELEIA) that has a 48hp powerhead and carbs but everything else came off of the 40 hp. (Just in case that might cause my problem) It runs like a banshee at about 3000 rpms and above. Almost too good (I have a thread in the prop forums about that) The problem is anything below 3000 rpms it starts missing. Bad enough that no matter what I do I cannot make it idle reliably. Unfortunately I have no way to check the WOT timing as the manual requests. Everything else has been done per the manual, in order and adjusted from there. I even went back and "re-zeroed" all the linkage and carb adjustments again just to make sure. Still no-dice. At one point I ohmed out the coil and the primary circuit was high....at about .3 ohms, manual says .05-.15 ohms. Should I go ahead and replace the coil first? It will just a 1/2" gap with a spark tester. Looking for more ideas on what the problem may be. Thanks.
-Aaron

 

[GreenF350]

Re: Idle and low throttle problems...

No ideas huh? Well, I bought a coil today, just to make sure (it was also had some little cracks in the epoxy). Don't know when I will get the chance to install it, but I will report back with the results.
-Aaron

 

[Reggie08]

Re: Idle and low throttle problems...

You never mentioned if you rebuilt the carbs and checked to make sure the floats are set properly. Have you tried that first?

 

[GreenF350]

Re: Idle and low throttle problems...

Oh yeah, Sorry....Carbs have not been rebuilt, I did however have them apart and cleaned them really good with carb cleaner and compressed air. I do not have the tool that my manual calls for to adjust the float, but it appeared to be pretty close just going from experience with carbs in general. You don't happen to have the measurement for the floats by any chance?

 

[Reggie08]

Re: Idle and low throttle problems...

When you cleaned the carbs, did make doubly sure all the orifice's and jets were thoroughly cleaned out? They have to be spotless.

As for the float, generally speaking, if you turn the carb upside down with the float installed, set the float so it's parallell or level with the carb body. To adjust it, you can usually bend the float tab a little until it's aligned.

I'm no expert, but your symptoms sounded eerily similar to a problem I just encountered and when I checked my carbs, the float on the top carb was mis-adjusted. I re-adjusted it and it runs great now. And since this is something you can check/fix with nothing more than your time, it's a good place to start IMO.

 

[GreenF350]

Re: Idle and low throttle problems...

Roger that! When I get the chance to go out and change the coil I will recheck the carbs, although I don't know if it was perfect, but the floats were close to level using the method you described. (It is similar on motorcycle and ATV carbs as well and I am more familiar with them). I am as sure as I can be that all of the jets and orifices were cleaned out. The carbs were supposedly freshly rebuilt before I got them and they looked pretty clean. I sprayed the crap out of them with carb cleaner and sprayed compressed air into all of the holes and stuff. Hopefully one of those two things will fix it. Thanks for the info. I will let you all know how it goes.

-Aaron

 

[GreenF350]

Re: Idle and low throttle problems...

Ok....Sorry to keep dragging this out, especially since I haven't re-checked the carbs yet, but I have connected another possible symptom of this problem.

My tach will intermittently jump up and looks like it is doubling the RPM's. It only does this in the RPM range I am having the problem in, as far as I can I can tell anyway. It seems rock solid in the upper RPM's. I had noticed it before, but for some reason I just chalked it up to an old, malfunctioning tach. Does the tach on a boat work in the same method as a car/motorcycle by "counting" the number of times a spark plug is fired? If so, does this sound like the ignition module? I will get the flywheel off tomorrow. For some reason it was on tight enough that it broke a bolt on my puller....Need to go to the hardware store tomorrow.
-Aaron

 

[GreenF350]

Re: Idle and low throttle problems...

Well, It's fixed (At least it runs WAY better now, I guess I won't know for sure until I get it in the water). Looks like it was the ignition module. The tach still isn't right, but I guess maybe the tach is just messed up. Go figure. Thanks.
-Aaron