85 hp thump noise at idle expert advice!

Joe Fisherman

Seaman
Joined
Feb 16, 2003
Messages
56
1977 85 hp johnny I just installed a carb kit to get going for the new season and at the river In idle I get a ramdom thumping noise out of the prop area then becomes more rapid every 5 seconds 2 or three times until motor dies. If i run at medium speed or full throttle I have no prolbems at all.After a full throttle run when shift back to idle it idles good for abount 20 seconds then starts the thumping process again until it stalls.This is not a shifting problem.Happens in neutral. Any thoughts would be appreciated?????? Pressure excaping improperly???
 
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