I'm just curious as to why a 50wt oil is so highly recommended in the marine arena? I'm going to run Amsoil 10W40 in my 600" mill and I feel it will be more than adequate. If your oil temps are less than 230*, and the clearances in the motor are correct I personally don't see the need to push any heavier than a 40wt. I personally think running something with a 50 attached to it creates a "feel good" false safety factor situation, but it also robs some HP as well as loads the oil pump, cam and timing set more. Just curious on opinions here.
Thanks,
Craig