Not strictly auto, tho close. I'm working on a 3 Litre boat motor & found that covering the carby throat didn't make a damn bit of difference to the motors rev's added to that it didn't try to suck my hand into it. It idles a little rough though not bad. There's no obvious mixture screw so can't alter that. So were the hell is it getting it's air from?? The Mercruiser alpha 1 is a 2002 4 cyl electronic ignition model. Googl ing I didn't find any reference to this problem. I've little to no experience with Mercruisers, though it's only a small truck engine marinised as far as I know.