carb issue?

Motor is a J150exeue. 1997 150hp carbed. The motor will not go above 4200rpm as of yesterday. Got home and put the motor on muffs and let idle for five minutes and took off the cover. I decided to check the carbs to see if they were working properly. I put my hand over each carb's intake manifold one by one. The top right carb when i took hand off the intake no gas came pouring out like the rest of the carbs did. Is this my issue with the carb not feeding gas to the motor?

When you put your hand over the throat of a carburetor of a running engine, you are acting as a manual choke.

From what you're said above, I would assume that on five (5) of the carburetors the rpms dropped down somewhat due to a flooding condition... and on one carburetor, there was no change in the rpm.

On that quiet carburetor, drain the float chamber, then run the engine to see if fuel is being freshly supplied to the float chamber... a test to make sure that the fuel supply line to that particular carburetor hasn't become restricted, plugged, whatever.

Next, remove all spark plugs and take a compression check of all cylinders. What are the psi readings of the individual cylinders?

With the spark plugs still removed, check the spark which should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it? Note that the 7/16" gap is important... testing the spark by using the spark plugs is a waste of time. *** No tester, see the following:

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

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Now, if you have proper spark and compression and fuel is being supplied to the quiet carburetor, the remaining component to suspect would be one or more of the leaf valve (broken, cracked, stuck open) attached to the reed plate assembly related to that quiet carburetor.