1969 johnson 85 hp carburetor icing

[smilz4uxo]

has anyone ever had this happen? the boat runs real bad and when i felt the carbs they were ice cold......can someone please give me some info on this.

 

[plugga]

Re: 1969 johnson 85 hp carburetor icing

i'm no expert on such things but for what its worth:<br /><br />any alcohol in your fuel?<br /><br />does it happen all the time or only under certain<br />weather conditions?<br /><br />what throttle position?<br /><br />i would have thought ice cold carbs would be good for power, as long as fuel vaporises fully. i also thought fully vaporising fuel caused ice cold carbs???<br /><br />have a look at some light aviation web sites/boards its a common problem on aircraft

 

[Tolly family]

Re: 1969 johnson 85 hp carburetor icing

I am a pilot and we are all familiar with this, air going thru your venturi increases in velocity and the temp drops causing ice to form until your engine is warm enough to heat the carb. Worst conditions are 40-50 degrees and humid. This is why your car has a heat risor pipe from the exhaust manifold to the air cleaner. If it is iced up shut down and wait a few minutes for the carb to warm up. My big boat has the same problems, runs great for the first 5 minutes then won't idle until fully warm.<br /><br />Dan