Mercury 60 hp 1984 - air control

[siedenburg]

Hi - have a new to me - 84 - I believe - brown stripe, running a 1966 MFG Westfield. Engine throttled up fine in the driveway but, started fine and ran at slow speed, but cuts out upon acceleration in the water. Taking the front cover plate off solved the problem. The air ports in the cover casing are clear -
Any advise on the adjustment to correct so the engine it can operate with the cover on?

Thanks