SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: not fast enough on June 22, 2016, 02:51:42 PM
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Hi guys new to the page just got a jet boat and it has a 454 with a demon 850cfm double pumper. Second pumper wouldn't work on the carb so I rebuilt the carb and fixed the problem but the thing is running was richer than it already was and now is flooding itself and not wanting to start after I stop. Just wondering if anyone has ran this setup and found a jet size that works good before I have to buy a new carburetor. Thanks
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Check float level
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Are the floats set ...
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3rd on it being a float issue. Possibly some debris caught in the needle and seat.
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https://www.google.com/url?sa=t&source=web&rct=j&url=http://static.speedwaymotors.com/pdf/91012054.pdf&ved=0ahUKEwj--Z-p2bzNAhVM02MKHatiDR0QFggiMAI&usg=AFQjCNG2bZgicLbMyeH8lZZsf3atzkmJBg&sig2=t6SQcERt9dwXoVCuEVD44Q
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Brand new needle and seat floats set in the middle of the eyeglass. I checked that already. Carb was running rich primary to being cleaned out now it is extremely rich
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I've went through everything and I know the thing needs a rejet. I was just trying to get a baseline of what jet sizes people are running on stock 454's with a 850 carb
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Well don't know if this is gonna help ya or not. I've got a holley 750 on a 502 and I'm pretty sure I'm running .084" jets currently.
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You prob have the idle cracked open to far and it's pulling fuel from the carb and not the idle circuit... With the carb off the transition slot should be square and not rectangle! It not it will idle so fat it will burn your eyes...
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Well don't know if this is gonna help ya or not. I've got a holley 750 on a 502 and I'm pretty sure I'm running .084" jets currently.
Thank you!
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You prob have the idle cracked open to far and it's pulling fuel from the carb and not the idle circuit... With the carb off the transition slot should be square and not rectangle! It not it will idle so fat it will burn your eyes...
Hmm we fired it up in the garage last weekend and had to get out because my eyes were watering so bad. I will have to check this out
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Usually the factory jetting is going to be pretty close, then only requiring small adjustments for tuning. If this carb still has the original jetting I'd say you have another issue causing you problems.
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But would the factory jetting on an 850 be set up for a stock 454?
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But would the factory jetting on an 850 be set up for a stock 454?
If it was going into a 78 Chevy pick up truck I'd say it was too much, but going into a jet boat it'll be just about right. It's difficult to over-carb a jet boat.