Carb rebuild then dies immediately with no idle

Buf-T

Recruit
Joined
Jun 15, 2020
Messages
4
My boat went into winter without fogging the engine/carb. Coming out of storage, couldn't get fuel to the carb. Figured likely carb gummed up, so purchased carb rebuild kit and rebuilt carb. I have an OMCobra 5.0FL engine. Model# 502APHUE, SN: T01280724. Dealer gave me rebuild kit PN, which was obsolete and I ordered from a shop out of state, OEM PN: 3854106.
After the rebuild, and after putting some suction to the fuel line to get fuel up to the carb inlet, the engine starts and runs, with full throttle, but as soon as the throttle drops below where the accelerator pump engages, engine dies immediately. It's as if the idle circuit is blocked. the idle adjustment screws on each side of the metering plate, don't seem to make a difference. It seems like there is more smoke than usual, but I never let the engine run long out of water in years prior when it kicked right over after storage. FYI - I blasted the heck out of the metering plate with carb cleaner when it was out. Everything I looked like in the carb looked in good shape. Is there a way to tell/see if the idle circuit is blocked? What else should I be checking? thanks much. btw: I'm a carb rebuild rookie.
 

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Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,499
Go back and actually clean your carb. Your idle passages are plugged. Spraying it with carb cleaner wont cut it. Pull the carb apart, soak for 3-4 hours minimum in a good carb cleaner. Berrymans at a minimum. Then chase every passage with a fine wire or fishing line.

Then set up the carb per the holley spec. At a minimum, use the factory manual
 

Tstew

Cadet
Joined
May 28, 2020
Messages
10
Hi,
also check to make sure there are no vacuum leaks. This will cause hard starting, and only starting at 3/4 to almost full throttle and will die when you back throttle off.
ck vacuum lines and plugs on carb as well as where it bolts to manifold
 

Tstew

Cadet
Joined
May 28, 2020
Messages
10
Hi,
also check to make sure there are no vacuum leaks. This will cause hard starting, and only starting at 3/4 to almost full throttle and will die when you back throttle off.
ck vacuum lines and plugs on carb as well as where it bolts to manifold
 

Buf-T

Recruit
Joined
Jun 15, 2020
Messages
4
Thanks all. I found the barryman's at the local autoshop, disassembled, gave it a good cleaning, reassembled and it runs like a top.
 
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