Rpm issues, carburation?

betayv

Senior Chief Petty Officer
Joined
May 13, 2008
Messages
706
hello guys 1987 searay with 5.7 engine, and a Rochester 4 barrel quadrajet, I start the engine with hose and Rpm are 725 on idle , after minutes drop to 600-575, any advice thanks.
 

alldodge

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Mar 8, 2009
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hello guys 1987 searay with 5.7 engine, and a Rochester 4 barrel quadrajet, I start the engine with hose and Rpm are 725 on idle , after minutes drop to 600-575, any advice thanks.

Have you tried to adjust the choke? After the engine warms totally up what does it idle at?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Is it still the original MARINE carb, or has it been changed out for a standard automotive? What you describe sounds like it's dropping off the fast idle cam (which marine carbs don't have)....
 

NHGuy

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May 21, 2009
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3,631
With the engine warm and choke open you should have about 675- 700 rpm at idle, in gear.
 
Last edited:

betayv

Senior Chief Petty Officer
Joined
May 13, 2008
Messages
706
hi guys this carburetor doens't have a choke and yes is a marine caruburetor, by the way the carburetor was rebuild by a carburetor shop.
 

tank1949

Lieutenant Commander
Joined
Apr 4, 2013
Messages
1,900
Could have some "slop" in linkage. Mine does and I get similar issues but not as bad. Make sure trash not in bowl after setting and sucking up alcolhol for some time. Make sure gas filters are clean and then pop off airhorn from carb main body. Remove float and look for crap. If no crap, put back together with breather off and run up at idle. Loosen throttle arm and manually accelerate motor while carefully placing palm of hand over primary carb air entrance. Motor will want to stall so advance throttle accordingly or lessen had covering to keep motor running. Do this a few times to suck any small particles out of "hidden" places. This is scarry but it works!
 
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