Spitting back thru exhaust at idle

[gf883]

I have twin 1990 200 ETXDs of original build on my Grady. They are well maintained and run great. Yesterday, my starboard motor Started spitting back thru the exhaust causing the engine to stall. This only occurs at idle in nuetral. If the engines are in gear I can idle at 600 rpms and it wont spit back. The engines spool up to 5300 rpms at wot and seem to run fine. I checked compression on all cylinders and its at 122-130 psi. I changed all plugs, cleaned the primary filter, and replaced the secondary filter. I also did a visual check for fuel leaks and found nothing appearent. Any ideas?

Thanks, Gary

[boats.net]

That is usually clogged low speed jets in carb, may need to remove and clean carbs.

[gf883]

The boat will idle at 650 rpms in gear all day long with out a hicup. Once I go to neutral it will idle smooth at 650 rpms for 15-20 seconds then spit and stall. Do you think it would still be the low speed jets? I will have the boat hauled out and rebuild the carbs if you think so.

Thanks Gary

P.S would a bad reed valve cause this to occur?

[jb123]

bad reed would spit out forward.