Hi. I have a 2002 Mercruiser 5.0L Gen+ with a Mercarb 2 barrel carburetor. Last year just before the season ended the carb got a new kit installed together with a ultrasound clean. That was because the rev jumped to 1500 rpm when put in neutral for 5-10 seconds and thereafter settled with around 650 rpm. i didn?t have a chance to test the rep./clean properly last year, but now i have just put her in the water again. Now the behavior is different. When put in neutral the rpm drops to around 650 and then jump slowly up and down between 650 and 1000 repeatedly. Any suggestion why that is?