EVINRUDE 90 hp v4 RUNS GOOD THEN BACKFIRES

raybow1

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Joined
Mar 27, 2010
Messages
17
Re: EVINRUDE 90 hp v4 RUNS GOOD THEN BACKFIRES

QuackAddict84:
Thank you for the detailed info on how to adjust the idle mixture screws. This sounds very resonable to me. I am going out Saturday to put it in the water. Thanks agin.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: EVINRUDE 90 hp v4 RUNS GOOD THEN BACKFIRES

The idle on that engine is unusual, as the carb butterflys are completely closed. The engine only draws fuel through the special idle passages in the upper carb body. When you go into forward, likely the carb butterflies will usually open slightly (with the throttle advance) and the carbs will start to draw fuel through the mids. That is probably why the lean sneezing stops-it is getting enough fuel. You can have pristine carbs and still have dried fuel in the idle passages in the upper carb body....causing a lean sneeze at idle only. The only want to verify is to compare the spray volumes of an aerosol carb cleaner with a passage on one carb, with the same passage on the other, etc.
 

raybow1

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Joined
Mar 27, 2010
Messages
17
Re: EVINRUDE 90 hp v4 RUNS GOOD THEN BACKFIRES

I finally got the aluminum float assy bodies and went to change them over only to notice that the internal jets inside the float assy are different thread size. Back to the parts house I went.:mad: No one could have known but what a pain in the butt as everything I do has to be ordered. Nothing is open opn the weekends either. The old jets were 1/4x20 thread pitch and the new ones needed for the aluminum assemblies were 8/32. What a thorn in my side. Well I finally got the carbs back together with the new parts and have not had a chance to test as of yet. I did notice the idle jets in the upper carb body are not adjustable. I removed all of them and it looked like one may have been partially blocked with some contaminants of some kind. I blew them out with air on a clean white absorbant towel and the one looked like a couple of pieces of fine matter may have been lodged. I am going to try it out and I hope this may finally solve my issue.

emdsapmgr: Thank you for the advice
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: EVINRUDE 90 hp v4 RUNS GOOD THEN BACKFIRES

You should have had to replace the drain plugs on the bowls also. They should also be a different size.This swap is definitely worth the aggrivation.
 
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raybow1

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Joined
Mar 27, 2010
Messages
17
Re: EVINRUDE 90 hp v4 RUNS GOOD THEN BACKFIRES

emdsapmgr; You are right I did have to replace the drain plugs also. Those parts actually came with the assemblies but the internal jets did not. I can understand why as I am sure there are many options available but it would have been nice to know at the time of order as we could have got those at the same time. I am on the same page with you on it being worth it as it is the peace of mind in knowing that the bowl assemblies are sealing in all the propper areas internally. My theory is that it does not matter how good the motor is if you have bad carbs the motor will go as the carbs go. If the motor is solid and the carbs are solid then you have the potential to make it run the way it did from the factory and that is ultimately what I am trying to get to. We then may stand a chance of having a good motor for a long time. I am really glad I found this web site as you guys seem to know these motors inside and out. This is actually the first outboard I have tackled troubleshooting. Thanks for the advice as it is greatly appreciated.
 

earivett

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Joined
Aug 16, 2011
Messages
1
Re: EVINRUDE 90 hp v4 RUNS GOOD THEN BACKFIRES

What is the part number for the #8-32 56C carb jet? I can find the 1/4-20 56C carb jet but can not find the jet for the aluminum float bowl.
 
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