Tony can you tell me the initial settings for carbs

I am an OMC guy but got gave

I am an OMC guy but got gave a 300 Merc. She has good compression and spark and I have cleaned the carbs abd jets. There is a thumb screw jet below the throat on each carb and also a slotted jey on the side of each carb. Could you please tell me the inital setting for these jets? Thanks much in advance!
BC

"B.C.

These carbs had some

"B.C.

These carbs had some minor differences, but were essentially the same.

The screw below the throat should be a plug. Inside you will find the main jet. This should not be adjustable. Both the plug and jet screw out, but if it does not seem to be gummed up in there, I would leave them alone; sometimes they simply will not come out anyway.

The slotted screw is the idle mixture adjustment. It can be on the front of the carb, above the bore, or on the side. You can start by lightly seating this screw, then backing it out 1 1/2 turns. After starting, you may find that the engine idles better if you lean this adjustment a bit. Do this in increments of 1/8 turn and see how it affects the idle. You may find that it improves as you lean this mixture screw. If you go as far as a half turn it will probably start to get rough, but it varies from engine to engine.

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