re - the heat riser discussion of a few days ago; icing is a very real problem, esp. on the 63-4's as they dont have heat risers on the long rams, they have an exh. gas diversion scheme that doesnt always work well enough to combat icing in the tubes. ive twice had hydrostatic locks due to melting ice from the intake tubes, ive gone so far as to install an ign cut out that allows me to roll the engine over, before starting, to ensure its clear of water, before starting on cold, damp days. JEFF tucson az.