Marine Qjet suddenly flooding

[7421f]

I have a pair of marine 454-350HP Crusaders with Qjets that were running great yesterday, but today, one engine is flooding badly. I thought the choke was stuck, but ruled that out. Black smoke and raw fuel smell and evidence of raw fuel in exhaust. Won't idle unless I keep rpms above 900. Flo-Scan shows the troubled engine using 2 gal per hour MORE than the good engine @ 900 rpms. I tried tapping the carb thinking the float was stuck open no difference noted. I have electric fuel pumps feeding the Qjets. Any thoughts on what could cause this sudden onset of flooding and how to fix it quickly as Labor Day weekend approaches and the wife wants to go boating with 2 engines.........

[Cliff Ruggles]

The carb needs to come apart.  I would install one of our kits, they contain much better components for this new fuel. 

It could be as simple as a piece of dirt/debris, but if the top is off, gaskets are needed, and it's a good time for a new float, fuel filter, accl pump, etc.....Cliff

[7421f]

That's what I was thinking,  but hoped I could do a quick fix for this weekend then order up my parts and completely go through it. I only use non-ethanol fuel and use Marine Formula STA-BIL® Ethanol Treatment.
I will get the numbers off the carb today. How quickly can I get a Kit to 98683?

[Cliff Ruggles]

Priority mail is usually 2 days, and inexpensive.  Next day air is really high to the West Coast....Cliff

[7421f]

I may have found the issue, or at least another one. I have the divorced choke on my intake. I started the troubled engine with the hatch off and observed soot blow from under the divorced choke when the engine stumbled. The bolts were about a half a turn loose. I tightened them and there was  an immediate improvement. Should I look at replacing the gasket on that or can I use hi-temp RTV? Could this be the cause of my issue?

[Cliff Ruggles]

Not sure?  That would be an exhaust crossover leak, not a vacuum leak.....Cliff

[Zac Agee]

at the machine shop we use red high temp silicon to seal of the exhaust crossovers on our B.S.A. cars that you can't modify the cylinder heads we just fill the entire hole with it but your better replacing the gaskets if anymore troubles with it. a few of our drag racers use high temp rtv instead of exhaust gaskets in general but they get torn down once a year guaranteed but I've yet to see the silicon burn up.

On another note I'm a fellow west coast customer and usually takes 5-7 days to get anything but well worth the wait thnx cliff!