I have a 2015 eskimo stingray 33cc auger Viper engine. I had it running great before I left the house. We got on the lake and it wouldn't start. I have done everything I can think of. I cleaned the carbs, replaced fuel line and filter. Drained and cleaned the tank, replaced grommets and spark plug. Air filter was cleaned, primer bulb works and everything seems in order. I have good compression, fresh fuel. The only way I can get it to stay running is if I have the throttle held down and slightly pressing the prime bulb continuously. What am I missing that could cause it not to run proper?