470 stalling during idling.

[DaleGribble]

Hi guys,
I have a 77' V20 with a Mercruiser 470,during idling after about 5 minutes the boat completely stalls and wont start for about 20 mins,had the carb rebuilt twice by reputable mechanics,new spark plugs and wires new fuel filter,fuel/water. Tanks were stabilized before winter and fresh fuel has been put in. Runs great at full throttle but need idle for crabbing,any suggestions for a rookie?

[spareparts]

those early 470's have the good carbs on them, if you haven't already. Do a compression test. Check your timing. I highly recommend doing an electronic conversion on the distributor(it will help with the idle issue). try and set the idle mixture screws with the boat in the water, it should idle right around 750-800 rpm. Look down the throat of the carb, if you have fuel dripping off the boosters, you have the idle speed screw set too high. Start with the idle mixture screws at about 1 1/2 turns out from lightly bottomed out