Engine dies when put in gear

I am a new boater and have an 1986 Gibson with twin Mercruiser 350CI engines . Had one carb rebuilt and now when put in gear at idle starboard engine dies. Close choke about 2/3 and seems to run ok. Mechanic thinks air leak or vacum issue. Any ideas?

Welcome to the forum.

You may get more replies by selecting the correct board (mercruiser). Also helps if you supply all the detail you can.

Guessing that the problem engine (stbd) had the rebuilt carb, were the idle mixture screws set correctly? idle speed adjusted after the mixture screws?

If the carb was reinstalled with the base gasket from a rochester kit, it will quite likely leak. A vacuum gauge will verify this.

If your

Close choke about 2/3 and seems to run ok

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refers to the engine that dies, I'd suspect the 'rebuild' was done without cleaning out the idle passages thoroughly.