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What is the part that the red arrow in the attached picture is pointing to? It is attached to the carb on the right side with an electrical connector on it. I want to replace it because the left electrical connector (red wire) is broken on it. And maybe where I could find the part? It is on a Holley 80456-1 Carb / 5.8L PCM / 96 Moomba Bommerang. I am having problems with backfire out of the carb under high loads only. It might not fix the problem, but I would still like to replace it.
There is a spring inside the case and when the boat is on power is supplied though those wires warming the spring which in turn relaxes the spring and opens the choke plate. It can be adjusted by loosening the screwing and rotating it either direction.
I guess maybe you would call it an electric choke thermosat.
Electric choke cap as noted by Sharpie. There are millions of these floating around out there, so take a trip to the junkyard, or just search on eBay for "Holley electric choke cap". They are about $15 there.
With your electrical connection being broken, your choke will stay closed much longer than it needs to and you'll be running rich until ambient temps warm the choke spring enough for it to finally open the choke. Not entirely sure it's the cause of your backfire, but you'll save the $15 in gas cost alone pretty quickly by replacing this.
Thanks for the quick replies. I believe the Holley Model 4160 is the same as mine, so I order one through my local O'Riley's. Part # 45-258. Now, to see if I can fix my backfire problem.
Thanks again
Id be leaning more at timming or timming advance issue from the distributor.
Backfire is due to a Valve being open when the cylinder fires. Backfire threw the carb means your timming is advanced too fare. So under heavy load the timming is advanced to its maximum and starts to backfire threw the carb. This is very dangerous as the carb can explode or at the very least catch fire.
You can verify this really easy, just retard the timming by 2 or 3 degrees using a timming light while the engine is at idle, normal base starting timming is 10 degrees, if your at say 12-15 at idle then dial it back 3 degrees, run the boat and see if it helps.
Other way to do this if you got the stone and the distrubutor is easy to reach and safe to reach.
Losen the distributor bolt till you can manualy turn the distributor, leave it snug though as you dont want to the engine turning it. On the bottom of the distributor is a gear that drives it and its ran by the oil pump. Get the boat up on plane or right about where it wants to start backfireing and turn the distributor slightly and you will notice the engine power change, it will stop backfireing or get worse all the sudden, twist it in the direction that is improving it till it sounds best or feels best by engine vibrations. Then bring her back to idle and tighten the bolt.
Thanks mmandley, I will try the distrubutor method this weekend. I already loosened it up just enough so I can turn it by hand on the lake. Does it matter that the carb only has carbon buildup and is all black on one side or is that normal for a carb the backfires?Attachment 14409